Re: [Elecraft] KPA500 Failure

[Mark Musick]

Dick,
Here is a link to information on many Elecraft products.

https://www.qsl.net/wb4kdi/Elecraft/index.html

Scroll down and you will see the KPA500.
You will see the schematic links.
Select the Low Pass Filter. It is REV D2 dated 12/5/13. I believe that is the 
latest.
The schematic I have is from 1/30/11.

73,
Mark, WB9CIF

-Original Message-
From: elecraft-boun...@mailman.qth.net  On 
Behalf Of Dick Bingham
Sent: Thursday, May 2, 2024 02:16
To: elecraft@mailman.qth.net
Subject: [Elecraft] KPA500 Failure

-- An update on my KPA500 failure --

I extracted the amplifier/LPF assembly from the case and examined the two units:

- Power FETs and all components *appear* to be OK
- *LPF Module Rev D* bd appears to be what failed. The
  SM component positioned between C97, C110 and
  C111 *MAY* be C96 - hard to identify after cleaning the
  white vapor-deposited 'stuff' from the PCA using
  acetone solvent. There was what appeared to be a
  "tombstone-positioned" '*something*' sitting on a pad
  in the damaged area that I can not identify.

I have not been able to locate a schematic or PCA picture for this LPF assembly 
to identify the missing component. If someone could provide a link to the Rev D 
LPF assy, I would appreciate it very much.

73 and TU to all who have, so-far, provided helpful suggestions. I am now 
waiting to hear what Elecraft's Service Department has to say about the failure 
info and picture I sent to them today.

Dick/w7wkr
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Re: [Elecraft] KPA500 metering

[W3FPR]

A 1.5 KW external wattmeter is much less expensive than a major KPA500 
repair - I would not risk it.


73,
Don W3FPR

On 4/3/2024 6:15 PM, Mike Murray wrote:

If a KPA500 is in standby, can it be used to determine power output from
another amp by feeding the signal thru the KPA?  I don't currently have an
external power meter I can utilize to check output of an SB200, but I also
don't want to risk damaging the KPA.

73,
Mike - W0AG
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Re: [Elecraft] KPA500 metering

[Ken Winterling]

Check the KPA500 manual. From memory, the max throughput in standby is
200W. As I say, check my memory against the manual.

*Ken*
*WA2LBI*




On Wed, Apr 3, 2024 at 6:36 PM Mike Murray  wrote:

> If a KPA500 is in standby, can it be used to determine power output from
> another amp by feeding the signal thru the KPA?  I don't currently have an
> external power meter I can utilize to check output of an SB200, but I also
> don't want to risk damaging the KPA.
>
> 73,
> Mike - W0AG
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Re: [Elecraft] KPA500

[AL7CR]

Check eBay.  One was just listed.

On Mon, Mar 18, 2024, at 10:26 AM, Josep via Elecraft wrote:
> Looking for a KPA500 for my Remote station, does anyone have any that 
> don´t need/use anymore..?
> Thanks,
>
>
> 73, 
> JosepEA6BF
> BUG #256  -  CWOps #3072  -  FOC #2182 (ex 1724)  -  CTDXCC - HSC #2016
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Re: [Elecraft] KPA500 Receives Keying Signal but does not XMT

[G4GNX]

OK so are you sure that the cables have been connected exactly according to the 
KAT500 manual (page 5)?

When you power up the KPA500 (with the K3 already on) do you see the KPA500 
announce itself in the VFO-B area of the K3? 

73,
Alan - G4GNX
South Coast UK
Elecraft K4D / KPA500 / KAT500 / IC-9700




> On 5 Dec 2023, at 02:41, Peter M Iverson  wrote:
> 
> Yes, both cables are Elecraft 15-pin cables.
> 
> Sent from my iPhone//Pete
> 
>> On Dec 4, 2023, at 15:30, G4GNX  wrote:
>> 
>> Can we have a little more info please.
>> 
>> Do you have two 15pin cables, one from the K3 to the KAT500 and one from the 
>> KAT500 to the KPA500?
>> 
>> Are the cables genuine Elecraft E850463 Aux Interface Cables or are they VGA 
>> style cables (which won’t work)?
>> 
>> You should not need any other cables connected to the setup apart from power 
>> and RF.
>> 
>> Page 5 of the KAT500 user manual shows the correct cabling.
>> 
>> 73,
>> Alan - G4GNX
>> South Coast UK
>> Elecraft K4D / KPA500 / KAT500 / IC-9700
>> 
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Re: [Elecraft] KPA500 Receives Keying Signal but does not XMT

[Masadaman via Elecraft]

Can anybody tell me how to unsubscribe from this?

Sent from Yahoo Mail on Android 
 
  On Mon, Dec 4, 2023 at 6:34 PM, G4GNX wrote:   Can we have a 
little more info please.

Do you have two 15pin cables, one from the K3 to the KAT500 and one from the 
KAT500 to the KPA500?

Are the cables genuine Elecraft E850463 Aux Interface Cables or are they VGA 
style cables (which won’t work)?

You should not need any other cables connected to the setup apart from power 
and RF.

Page 5 of the KAT500 user manual shows the correct cabling.

73,
Alan - G4GNX
South Coast UK
Elecraft K4D / KPA500 / KAT500 / IC-9700



> On 4 Dec 2023, at 23:18, Peter Iverson  wrote:
> 
> Here’s the problem: I’ve been successfully running a K3/KPA500/LDG 
> AT-600ProII with no problems, usually USB and digital modes at about 400W 
> out. I recently obtained a KAT500 and replaced the LDG tuner. I used the 
> Elecraft 15-pin cables for full integration. The KPA500 follows the K3 when I 
> switch bands, but when I go from STBY to OPER, the KPA500 shows no output. 
> Neither SWR nor POWER led’s light up. I tried my original configuration with 
> the LDG tuner but same problem occurs—KPA500 no output. I know the K3 is 
> producing output because on STBY the LDG shows POWER and I’m making contacts 
> barefoot. I’ve even tried the basic hookup with RCA cables but no joy. The 
> KPA500 does show an asterisk in the left corner of the display when I key the 
> K3 so it is receiving a keying signal. I’ve checked to make sure I have the 
> latest firmware version and I’ve doubled checked to make sure that INHIB IN 
> is DISABLED in the menu. I’m running the KPA500 on 240V mains. I’m hoping 
> someone can help me solve this dilemma.
> 
> Pete
> KH6GK


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Re: [Elecraft] KPA500 Receives Keying Signal but does not XMT

[G4GNX]

Can we have a little more info please.

Do you have two 15pin cables, one from the K3 to the KAT500 and one from the 
KAT500 to the KPA500?

Are the cables genuine Elecraft E850463 Aux Interface Cables or are they VGA 
style cables (which won’t work)?

You should not need any other cables connected to the setup apart from power 
and RF.

Page 5 of the KAT500 user manual shows the correct cabling.

73,
Alan - G4GNX
South Coast UK
Elecraft K4D / KPA500 / KAT500 / IC-9700



> On 4 Dec 2023, at 23:18, Peter Iverson  wrote:
> 
> Here’s the problem: I’ve been successfully running a K3/KPA500/LDG 
> AT-600ProII with no problems, usually USB and digital modes at about 400W 
> out. I recently obtained a KAT500 and replaced the LDG tuner. I used the 
> Elecraft 15-pin cables for full integration. The KPA500 follows the K3 when I 
> switch bands, but when I go from STBY to OPER, the KPA500 shows no output. 
> Neither SWR nor POWER led’s light up. I tried my original configuration with 
> the LDG tuner but same problem occurs—KPA500 no output. I know the K3 is 
> producing output because on STBY the LDG shows POWER and I’m making contacts 
> barefoot. I’ve even tried the basic hookup with RCA cables but no joy. The 
> KPA500 does show an asterisk in the left corner of the display when I key the 
> K3 so it is receiving a keying signal. I’ve checked to make sure I have the 
> latest firmware version and I’ve doubled checked to make sure that INHIB IN 
> is DISABLED in the menu. I’m running the KPA500 on 240V mains. I’m hoping 
> someone can help me solve this dilemma.
> 
> Pete
> KH6GK


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Re: [Elecraft] KPA500 / KAT500 and W2 watt meter question

[Jack Brindle via Elecraft]

If you use the key-line interrupter, then you must use the phono-plug cables to 
connect the K3, KPA and KAT. Otherwise PTT will not get to the amplifier.
Of course using both without the key line interrupter is very redundant. You 
just don’t want to use both if an external device is included.

73,
Jack, W6FB


> On Oct 12, 2023, at 11:35 AM, Andy Durbin  wrote:
> 
> SteppIR will accept up to 200 W without damage and opening the amplifier key 
> line is the standard way protect SteppIR antennas.
> 
> It has been asserted that "NO key line interrupter is needed".  However, 
> Elecraft recognizes that they may be such a need and sells an adapter to 
> disable keying by AUX cable.  The description even mentions including the W2 
> is the protection system.
> 
> https://ftp.elecraft.com/KPA/Manuals%20Downloads/E740160%20-%20KPAK3AUX%20Cable%20Set%20Instructions%20Rev%201E.pdf
> 
> Andy, k3wyc
> 
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Re: [Elecraft] KPA500 / KAT500 and W2 watt meter question

[Andy Durbin]

SteppIR will accept up to 200 W without damage and opening the amplifier key 
line is the standard way protect SteppIR antennas.

It has been asserted that "NO key line interrupter is needed".  However, 
Elecraft recognizes that they may be such a need and sells an adapter to 
disable keying by AUX cable.  The description even mentions including the W2 is 
the protection system.

https://ftp.elecraft.com/KPA/Manuals%20Downloads/E740160%20-%20KPAK3AUX%20Cable%20Set%20Instructions%20Rev%201E.pdf

Andy, k3wyc

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Re: [Elecraft] KPA500 / KAT500 and W2 watt meter question

[Jack Brindle via Elecraft]

Key line interrupt would probably not be a good way since the transceiver is 
still transmitting, but at a lower level. All key line interrupt does is to 
disable the amplifier.
I would think a better way would be to use the K3’s inhibit input signal if you 
really need no tx power coming out.

Note that this has been handled in many, many stations to this point with few 
(or no) issues.

73,
Jack, W6FB


> On Oct 12, 2023, at 10:32 AM, Andy Durbin  wrote:
> 
> "In the KAT500 manual, page 5, Figure 1 Cabling Diagram, is the better and 
> safer way to configure the system.  NO key line interrupter is needed.
> 
> How does an Elecraft station that controls KPA500 and KAT500 using AUX cables 
> inhibit keying when a SteppIR antenna is moving the tapes?  This protection 
> must be provided or element tapes and brushes can be damaged.
> 
> Andy, k3wyc
> 
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Re: [Elecraft] KPA500 / KAT500 and W2 watt meter question

[Andy Durbin]

"In the KAT500 manual, page 5, Figure 1 Cabling Diagram, is the better and 
safer way to configure the system.  NO key line interrupter is needed.

How does an Elecraft station that controls KPA500 and KAT500 using AUX cables 
inhibit keying when a SteppIR antenna is moving the tapes?  This protection 
must be provided or element tapes and brushes can be damaged.

Andy, k3wyc

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Re: [Elecraft] KPA500 / KAT500 and W2 watt meter question

[Tom N4LSJ]

The KAT500 will interrupt the amp properly.  Radio key line goes to KAT, 
then KAT key line goes to KPA.  Coax is opposite: Rig to Amp, then Amp 
to Tuner, then Tuner to Antenna.


On 10/10/23 08:17, Glenn Maclean wrote:

I just ordered the KPA500/KAT500 combo and W2 watt meter for my K3S. Should I 
use the key line interrupt connected to the W2 watt meter or should I connect 
the key line interrupt to the KAT500? Do I even need to use key line interrupt 
with the K line set up?
Thanks in advance
Glenn WA7SPY

Sent from my iPhone
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Re: [Elecraft] KPA500 / KAT500 and W2 watt meter question

[Jack Brindle via Elecraft]

Glenn;

You will want the two Aux cables to connect the K3S to the KAT500, then the 
KAT500 to the KPA500. The cables are described in the equipment manuals.
When the KAT500 is in a tune or finds some error situation, it will negate the 
key line to the KPA500 until the KAT is able to correct the situation.

With this setup, you don’t need the key line interrupter that the W2 provides 
since the KAT500 is doing it for you.

If you need any help, just ask. We hope you really enjoy your KPA500/KAT500 
combination!

73,
Jack, W6FB


> On Oct 10, 2023, at 7:17 AM, Glenn Maclean  wrote:
> 
> I just ordered the KPA500/KAT500 combo and W2 watt meter for my K3S. Should I 
> use the key line interrupt connected to the W2 watt meter or should I connect 
> the key line interrupt to the KAT500? Do I even need to use key line 
> interrupt with the K line set up?
> Thanks in advance
> Glenn WA7SPY
> 
> Sent from my iPhone
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Re: [Elecraft] KPA500 / KAT500 and W2 watt meter question

[Dean L/ K2WW]

I don't see the original thread only Bob's reply?
I've noticed these broken thread quite frequently...Has anyone else see
this?

73
Dean K2WW

On Tue, Oct 10, 2023, 11:09 AM Bob McGraw  wrote:

> Glenn:
>
> In the KAT500 manual, page 5. Figure 1 Cabling Diagram is the better way
> to connect the items.  It does not use the key line interrupt. That is
> the configuration which I have used, very successfully, for years.
>
> In the K3S, set the MENU for 20 watts TUNE power, and from the CONFIG
> menu PWR SET to Per Band.
>
> 73
>
> Bob, K4TAX
>
>
>
> On 10/10/2023 7:18 AM, elecraft-requ...@mailman.qth.net wrote:
> > Message: 23 Date: Tue, 10 Oct 2023 05:17:26 -0700 From: Glenn Maclean
> >  To: elecraft@mailman.qth.net Subject: [Elecraft]
> > KPA500 / KAT500 and W2 watt meter question Message-ID:
> > <3a0e28e4-8411-4394-a880-0fec58bf3...@att.net> Content-Type:
> > text/plain; charset=us-ascii I just ordered the KPA500/KAT500 combo
> > and W2 watt meter for my K3S. Should I use the key line interrupt
> > connected to the W2 watt meter or should I connect the key line
> > interrupt to the KAT500? Do I even need to use key line interrupt with
> > the K line set up? Thanks in advance Glenn WA7SPY
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Re: [Elecraft] KPA500 / KAT500 Combo

[James Bennett via Elecraft]

The amp and tuner have been sold. Thanks for your interest.


> On Oct 4, 2023, at 4:27 PM, James Bennett via Elecraft 
>  wrote:
> 
> Time to clean house of items that are rarely used. I’m selling my KPA500 
> (serial # 3645) and KAT500 (serial #2726). Both were built by me a few years 
> ago and work perfectly. I started out using them with a K3, then a K4D, and 
> most recently a Kenwood TS-890. Both the tuner and the amp work perfectly. 
> Neither has any scratches, dings, or dents and have been used in 100 percent 
> non-smoking environments. The amp is set for 117 volt operation and includes 
> the correct power cable.
> 
> Included will be the following manuals: KPA500 Kit Assembly Instructions, 
> KPA500 Owner’s Manual, KAT500 Owner’s Manual, and the Fred Cady (KE7X, SK) 
> book on the KPA500 and KAT500, 2nd edition.
> 
> In addition you’ll get the interconnecting cables. I currently have the pair 
> connecting my TS-890. You’ll get the corresponding cable(s) for that 
> arrangement along with the cables to connect to a K3 or K4 if that’s what you 
> have.
> 
> The amp and tuner have been in use here at my Idaho QTH for 2-1/2 years, 
> connected to a Zerofive Flagpole Vertical. With 110 feet of RG213, the tuner 
> has been able to get a match on 160 - 6 meters, no small feat indeed! Sadly, 
> I simply don’t use the amp and tuner all that often, I need the dollars, so 
> they’ve gotta go.
> 
> The KPA500 will be shipped in an Elecraft factory double boxed carton. I’ll 
> have UPS professionally package up the KAT500.
> 
> I much prefer to sell the amp and tuner as one package, price: $2,900, FREE 
> SHIPPING, NO SALES TAX. Check the price for a brand new pair and add tax - my 
> price will save you some serious dollars!
> 
> I prefer PayPal friends and family, but will accept cash or personal check 
> (10 days to clear a check, sorry).
> 
> Please contact me off-list. K7TXA at ARRL DOT NET
> 
> Jim / K7TXA (ex-W6JHB)
> Eagle, ID
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Re: [Elecraft] KPA500 17M missing

[Jim Brown]

On 8/31/2023 2:45 PM, Henry Pfizenmayer via Elecraft wrote:

I have a friend across town who has a KPA500  built from a kit  Aug 2017 SN 
33XX who has never used his K3S or KPA500  on17 m and just got an antenna for 
17 and lo and behold NOTHING he does will allow operation on 17.


Hank,

Will the K3S transmit on 17M with the antenna connected directly to it?

73, Jim K9YC
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Re: [Elecraft] KPA500 gain variation with serial number

[Tom N4LSJ]

Mine was bought new in the Summer of 2022 and on most bands it needs 
watts to be in the mid to upper 30s to get the 500 out.


On 7/20/23 13:04, Andy Durbin wrote:

I have been told that the gain of the KPA500 has increased over the years it has been produced.   
"Early" KPA500 are reported to need 35-39 W to produce 500 W out. "Later" 
KPA500 are reported to need only 20-25 W for full output.  The difference in gain has been 
attributed to difference in the PA transistors as well as component changes in the LPF.

I'm interested in knowing where my KPA500 serial number falls in the spread of 
required drive power.  I would like to receive data from KPA500 owners so I can 
get an idea of what gain can be associated with a serial number range.   To 
minimize the spread of data I'd like to specify 20 m band,  non reactive 50 ohm 
load,  key down CW mode.  It would be preferable for drive power and output 
power to be measured with the same instrument but I'll take what I can get.  If 
a KAT500 or other tuner is in circuit it should be in Bypass mode.

Requested data:

Serial number;  frequency; drive power; output power (target 500 W); PA voltage 
(front panel HV); PA current (front panel CUR); power measurement instrument(s).

Only one data point for 20 m band is requested but additional data won't be 
discarded.   I'll collate any data and share it if here is any interest.

Thanks and 73,
Andy, k3wyc




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Re: [Elecraft] KPA500 gain variation with serial number

[Dave (NK7Z)]

Andy,

Pitch out the highest, and lowest, and it looks fairly flat...

73, and thanks,
Dave (NK7Z)
https://www.nk7z.net
ARRL Volunteer Examiner
ARRL Technical Specialist, RFI
ARRL Asst. Director, NW Division, Technical Resources

On 7/26/23 11:00, Andy Durbin wrote:

I now have data for nine KPA500 with serial numbers ranging from 11x to 478x 
(exact serial number intentionally obscured).  Thanks to everyone who 
contributed.

The data show no significant increase in gain from the earliest to the latest 
serial numbers.  However, the data do seem to suggest that serial numbers near 
2,000  have gain well above average.

Perhaps the most interesting data came from one owner of two KPA500.  Serial 
209x had a gain of 14.4 dB but serial 478x had a gain of 12.0.  These numbers 
are from the same person using the same power measurement device and same 
measurement technique.

Lowest reported gain was 11.5 dB (2 samples) and one of those is mine.  There 
are three others at 11.8 dB.  All except 3 fall in the range 11.5 to 12.0.

Plot can be found here - 
https://www.dropbox.com/s/jk1t9j2417lh9gz/KPA500%2020%20m%20gain.png?dl=0

I also have some information on two other KPA500 that have high gain but I 
don't have serial numbers for them.  I'll update my plot if I receive any 
additional data.

73,
Andy, k3wyc


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Re: [Elecraft] KPA500 gain variation with serial number

[Andy Durbin]

I now have data for nine KPA500 with serial numbers ranging from 11x to 478x 
(exact serial number intentionally obscured).  Thanks to everyone who 
contributed.

The data show no significant increase in gain from the earliest to the latest 
serial numbers.  However, the data do seem to suggest that serial numbers near 
2,000  have gain well above average.

Perhaps the most interesting data came from one owner of two KPA500.  Serial 
209x had a gain of 14.4 dB but serial 478x had a gain of 12.0.  These numbers 
are from the same person using the same power measurement device and same 
measurement technique.

Lowest reported gain was 11.5 dB (2 samples) and one of those is mine.  There 
are three others at 11.8 dB.  All except 3 fall in the range 11.5 to 12.0.

Plot can be found here - 
https://www.dropbox.com/s/jk1t9j2417lh9gz/KPA500%2020%20m%20gain.png?dl=0

I also have some information on two other KPA500 that have high gain but I 
don't have serial numbers for them.  I'll update my plot if I receive any 
additional data.

73,
Andy, k3wyc


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Re: [Elecraft] KPA500 gain variation with serial number

[Andy Durbin]

Thanks to all those who have submitted test data.  I shall need more to have 
any hope of seeing a correlation so please keep it coming.

Requested data:

Serial number;  frequency; drive power; output power (target 500 W); PA voltage 
(front panel HV); PA current (front panel CUR); power measurement instrument(s).

Only one data point for 20 m band is requested but additional data won't be 
discarded.

Thanks and 73,
Andy, k3wyc


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Re: [Elecraft] KPA500 PA DISS fault

[Jim Brown]

On 7/16/2023 6:43 AM, Rajiv Dewan wrote:

What do you think I should check or do?


Call Elecraft support. Their service techs will likely have seen it before.

73, Jim K9YC
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Re: [Elecraft] KPA500 PA DISS fault

[Glenn Anderson]

I had the same problem about a year ago.  It's a problem with the output PIN 
diode switch. There will be a burned toroid in the output switch circuit. I 
sent mine back for repair. It's been working fine since.Good luck,Glenn WB5TUF 
 Original message From: Rajiv Dewan  Date: 
7/16/23  08:45  (GMT-06:00) To: elecraft@mailman.qth.net Subject: [Elecraft] 
KPA500 PA DISS fault Hello,   My KPA500 developed a PA DISS fault right the 
start of the VHF contest operating FT8 on 6m.  It is:* showing this message on 
all bands.   The antenna is fine.  (1.2 SWR)* same fault even when feeding a 
good dummy load* I smelt acrid smoke :(What do you think I should check or 
do?Thanks for any tips,Best,Raj N2RD-- --Rajiv Dewan, 
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Re: [Elecraft] KPA500

[EA6BF, Josep via Elecraft]

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Re: [Elecraft] KPA500

[Ian Kahn]

There are also taps inside the KPA500 that need to be set correctly, for
the voltage you wish to use. The assembly manual fully describes setting
the taps appropriately, for your desired voltage.

73 de,

Ian, NV4C

On Mon, Jun 5, 2023, 10:58 AM Irwin KD3TB  wrote:

> Joe,
> On the back of the KPA 500 you will find a fuse plug. You will switch this
> between voltages using different fusses. Be careful to use the correct
> fusses for the specific voltage. You can find the directions in the manual.
>
> Irwin KD3TB
>
> On Mon, Jun 5, 2023 at 7:03 AM Josep via Elecraft <
> elecraft@mailman.qth.net>
> wrote:
>
> > Hi guys,
> > just a question.I have recently bought a KPA500 (#0762) in the US.I
> > have another one at home that a friend of mine built for me in the US.I
> > know the amplifier works 100-120VAC and 200-240VAC so the question is if
> I
> > need to switch some kinda interruptor inside the amplifier.I need to know
> > that so when it comes here I can check wether its set, to 110VAC or
> 240VAC,
> > and correct it if needed.
> > Thanks for help.
> >
> >
> > 73,
> > JosepEA6BFMyWebsiteBUG #256  -  CWOps #3072  -  FOC #2182 (ex 1724)
> > __
> > Elecraft mailing list
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>
> --
> Irwin KD3TB
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Re: [Elecraft] KPA500

[Irwin KD3TB]

Joe,
On the back of the KPA 500 you will find a fuse plug. You will switch this
between voltages using different fusses. Be careful to use the correct
fusses for the specific voltage. You can find the directions in the manual.

Irwin KD3TB

On Mon, Jun 5, 2023 at 7:03 AM Josep via Elecraft 
wrote:

> Hi guys,
> just a question.I have recently bought a KPA500 (#0762) in the US.I
> have another one at home that a friend of mine built for me in the US.I
> know the amplifier works 100-120VAC and 200-240VAC so the question is if I
> need to switch some kinda interruptor inside the amplifier.I need to know
> that so when it comes here I can check wether its set, to 110VAC or 240VAC,
> and correct it if needed.
> Thanks for help.
>
>
> 73,
> JosepEA6BFMyWebsiteBUG #256  -  CWOps #3072  -  FOC #2182 (ex 1724)
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-- 
Irwin KD3TB
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Re: [Elecraft] KPA500 Fan Question

[Jack Brindle via Elecraft]

Hi Jim!
Hope you are enjoying Idaho. I hear it is a great place to be!

The fan in the KPA500 goes to level 3 at 60 degrees. It goes to full-on at 80 
degrees. 
The levels are:
level 1 - 50C degrees
level 2 - 55C degrees
level 3 - 60C degrees
level 4 - 65C degrees
level 5 - 70C degrees
level 6 - 80C degrees
The amplifier will fault at a temperature is 90C.

What mode are you operating? And, for those using TS-890s, why would the KPA 
behave any differently than it does with a K3? Has anyone checked for spurs or 
harmonics coming out of the transmitter? (NOT suggesting there are any, mind 
you). I’m looking for reasons the KPA would heat up any faster than with a K3. 
Are you seeing anything else, like strange band changes?

But, rest assured that the KPA will run just fine at 60 or 65 degrees. The fan 
sound is just telling you the KPA is doing its normal great job at protecting 
itself.

73,
Jack, W6FB
p.s. I didn’t want the snow, so I went the other way, going home to Louisiana…


> On May 14, 2023, at 12:23 PM, James Bennett via Elecraft 
>  wrote:
> 
> Got a question (problem?) regarding the fan in my KPA500. I'm driving the amp 
> at 29 watts from a Kenwood TS-890S. The amp is connected to a KAT500, which 
> in turn is hooked to a 30 foot tall Zerofive flagpole vertical. The tuner has 
> provided me with a nice 1.2:1 SWR, as displayed on the amp. The resting temp 
> of the amp shows 42C. At 29 watts input to the amp, I’m seeing about 480 
> watts of power from the amp. The amp has nothing sitting on top of it, and 
> the wall behind it is over 12” away. There is about 2” clearance on either 
> side of the amp, and it is sitting on top of the KAT500.
> 
> The issue: The fan comes on in a very short time - less than 20 seconds - and 
> the temp display runs up to 50+ degrees. If I start calling CQ or get into a 
> QSO, it doesn’t take long for the temp to show over 60 degrees and the fan is 
> running at max.
> 
> When I had a K3 and more recently, a K4D - this did NOT happen. The fan would 
> come on but NEVER at the max, loud level. Interestingly, many moons ago I 
> also had a KX3 and had it connected to the KPA500. I noticed that the fan 
> would also come on fairly quickly with that rig driving the amp, but I never 
> thought too much about it. Until now...
> 
> But now, I think there is some sort of problem. It seems to me that the temp 
> shouldn’t get that high that fast nor should the fan start roaring in that 
> short amount of time. I could understand it if the SWR was really bad, but at 
> 1.2:1
> 
> Any ideas why the amp fan should be acting this way with a non-K3 or non-K4 
> driving it?
> 
> Jim / K7TXA
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Re: [Elecraft] KPA500 Fan Question

[Peter Lascell]

My K3 into the KPA500 for over ten years . . . .   The FAN REV is 1.54
(this might be software)The resting temp is 27C.  When on RTTY I set
the FAN to 4.  Otherwise 2 for most of the time.  Knowing temperature is
the killer of electronics (short of lightning) I try to keep things cool.
For 10 years I have had a 24 V muffin fan running at 12 V sitting on top of
the amp (and another one on the K3).

To rule out VSWR issues, how about connecting the KPA500 directly into a
dummy load.

Pete W4WWQ

On Sun, May 14, 2023 at 1:24 PM James Bennett via Elecraft <
elecraft@mailman.qth.net> wrote:

> Got a question (problem?) regarding the fan in my KPA500. I'm driving the
> amp at 29 watts from a Kenwood TS-890S. The amp is connected to a KAT500,
> which in turn is hooked to a 30 foot tall Zerofive flagpole vertical. The
> tuner has provided me with a nice 1.2:1 SWR, as displayed on the amp. The
> resting temp of the amp shows 42C. At 29 watts input to the amp, I’m seeing
> about 480 watts of power from the amp. The amp has nothing sitting on top
> of it, and the wall behind it is over 12” away. There is about 2” clearance
> on either side of the amp, and it is sitting on top of the KAT500.
>
> The issue: The fan comes on in a very short time - less than 20 seconds -
> and the temp display runs up to 50+ degrees. If I start calling CQ or get
> into a QSO, it doesn’t take long for the temp to show over 60 degrees and
> the fan is running at max.
>
> When I had a K3 and more recently, a K4D - this did NOT happen. The fan
> would come on but NEVER at the max, loud level. Interestingly, many moons
> ago I also had a KX3 and had it connected to the KPA500. I noticed that the
> fan would also come on fairly quickly with that rig driving the amp, but I
> never thought too much about it. Until now...
>
> But now, I think there is some sort of problem. It seems to me that the
> temp shouldn’t get that high that fast nor should the fan start roaring in
> that short amount of time. I could understand it if the SWR was really bad,
> but at 1.2:1
>
> Any ideas why the amp fan should be acting this way with a non-K3 or
> non-K4 driving it?
>
> Jim / K7TXA
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-- 
Pete Lascell
Forest, VA
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Re: [Elecraft] KPA500 Fan Question

[AL7CR]

My setup is like yours and the response is exactly the same.   Starting use on 
fan speed 4 delays the temp rise for a short time. Mine has run many many  
hours at temps up to 70 with no problems.   Hottest on 20m and  requires the 
most drive on that band also. 

On Sun, May 14, 2023, at 10:23 AM, James Bennett via Elecraft wrote:
> Got a question (problem?) regarding the fan in my KPA500. I'm driving 
> the amp at 29 watts from a Kenwood TS-890S. The amp is connected to a 
> KAT500, which in turn is hooked to a 30 foot tall Zerofive flagpole 
> vertical. The tuner has provided me with a nice 1.2:1 SWR, as displayed 
> on the amp. The resting temp of the amp shows 42C. At 29 watts input to 
> the amp, I’m seeing about 480 watts of power from the amp. The amp has 
> nothing sitting on top of it, and the wall behind it is over 12” away. 
> There is about 2” clearance on either side of the amp, and it is 
> sitting on top of the KAT500.
>
> The issue: The fan comes on in a very short time - less than 20 seconds 
> - and the temp display runs up to 50+ degrees. If I start calling CQ or 
> get into a QSO, it doesn’t take long for the temp to show over 60 
> degrees and the fan is running at max.
>
> When I had a K3 and more recently, a K4D - this did NOT happen. The fan 
> would come on but NEVER at the max, loud level. Interestingly, many 
> moons ago I also had a KX3 and had it connected to the KPA500. I 
> noticed that the fan would also come on fairly quickly with that rig 
> driving the amp, but I never thought too much about it. Until now...
>
> But now, I think there is some sort of problem. It seems to me that the 
> temp shouldn’t get that high that fast nor should the fan start roaring 
> in that short amount of time. I could understand it if the SWR was 
> really bad, but at 1.2:1
>
> Any ideas why the amp fan should be acting this way with a non-K3 or 
> non-K4 driving it?
>
> Jim / K7TXA
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Re: [Elecraft] KPA500 Fan Question

[Mike Maloney]

 Your resting temperature at 42C seems TOO warm to me?   My KPA resting temp 
runs about the same as ambient temperature of shack, 25-30C.   With 25-30W 
drive from TS-890,my KPA seldom reaches 3rd stage 60 degrees.   Have you 
checked SWR or cable between 890 and KPA?  
73, Mike AC5P
On Sunday, May 14, 2023 at 12:38:56 PM CDT, James Bennett via Elecraft 
 wrote:  
 
 Yes, but the amp is not seeing the mis-match, correct? The tuner is taking 
care of that mis-match and I would have thought that the amp should be 
perfectly happy… Yes?

> On May 14, 2023, at 11:35 AM, Dr. William J. Schmidt  
> wrote:
> 
> You are trying to transform a mis-match and that burns energy.  That’s why 
> the fan is running.
> 
> 
> 
> 
> -Original Message-
> From: elecraft-boun...@mailman.qth.net  On 
> Behalf Of James Bennett via Elecraft
> Sent: Sunday, May 14, 2023 12:24 PM
> To: Elecraft Reflector Reflector 
> Subject: [Elecraft] KPA500 Fan Question
> 
> Got a question (problem?) regarding the fan in my KPA500. I'm driving the amp 
> at 29 watts from a Kenwood TS-890S. The amp is connected to a KAT500, which 
> in turn is hooked to a 30 foot tall Zerofive flagpole vertical. The tuner has 
> provided me with a nice 1.2:1 SWR, as displayed on the amp. The resting temp 
> of the amp shows 42C. At 29 watts input to the amp, I’m seeing about 480 
> watts of power from the amp. The amp has nothing sitting on top of it, and 
> the wall behind it is over 12” away. There is about 2” clearance on either 
> side of the amp, and it is sitting on top of the KAT500.
> 
> The issue: The fan comes on in a very short time - less than 20 seconds - and 
> the temp display runs up to 50+ degrees. If I start calling CQ or get into a 
> QSO, it doesn’t take long for the temp to show over 60 degrees and the fan is 
> running at max.
> 
> When I had a K3 and more recently, a K4D - this did NOT happen. The fan would 
> come on but NEVER at the max, loud level. Interestingly, many moons ago I 
> also had a KX3 and had it connected to the KPA500. I noticed that the fan 
> would also come on fairly quickly with that rig driving the amp, but I never 
> thought too much about it. Until now...
> 
> But now, I think there is some sort of problem. It seems to me that the temp 
> shouldn’t get that high that fast nor should the fan start roaring in that 
> short amount of time. I could understand it if the SWR was really bad, but at 
> 1.2:1
> 
> Any ideas why the amp fan should be acting this way with a non-K3 or non-K4 
> driving it?
> 
> Jim / K7TXA
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Re: [Elecraft] KPA500 Fan Question

[James Bennett via Elecraft]

Yes, but the amp is not seeing the mis-match, correct? The tuner is taking care 
of that mis-match and I would have thought that the amp should be perfectly 
happy… Yes?

> On May 14, 2023, at 11:35 AM, Dr. William J. Schmidt  
> wrote:
> 
> You are trying to transform a mis-match and that burns energy.  That’s why 
> the fan is running.
> 
> 
> 
> 
> -Original Message-
> From: elecraft-boun...@mailman.qth.net  On 
> Behalf Of James Bennett via Elecraft
> Sent: Sunday, May 14, 2023 12:24 PM
> To: Elecraft Reflector Reflector 
> Subject: [Elecraft] KPA500 Fan Question
> 
> Got a question (problem?) regarding the fan in my KPA500. I'm driving the amp 
> at 29 watts from a Kenwood TS-890S. The amp is connected to a KAT500, which 
> in turn is hooked to a 30 foot tall Zerofive flagpole vertical. The tuner has 
> provided me with a nice 1.2:1 SWR, as displayed on the amp. The resting temp 
> of the amp shows 42C. At 29 watts input to the amp, I’m seeing about 480 
> watts of power from the amp. The amp has nothing sitting on top of it, and 
> the wall behind it is over 12” away. There is about 2” clearance on either 
> side of the amp, and it is sitting on top of the KAT500.
> 
> The issue: The fan comes on in a very short time - less than 20 seconds - and 
> the temp display runs up to 50+ degrees. If I start calling CQ or get into a 
> QSO, it doesn’t take long for the temp to show over 60 degrees and the fan is 
> running at max.
> 
> When I had a K3 and more recently, a K4D - this did NOT happen. The fan would 
> come on but NEVER at the max, loud level. Interestingly, many moons ago I 
> also had a KX3 and had it connected to the KPA500. I noticed that the fan 
> would also come on fairly quickly with that rig driving the amp, but I never 
> thought too much about it. Until now...
> 
> But now, I think there is some sort of problem. It seems to me that the temp 
> shouldn’t get that high that fast nor should the fan start roaring in that 
> short amount of time. I could understand it if the SWR was really bad, but at 
> 1.2:1
> 
> Any ideas why the amp fan should be acting this way with a non-K3 or non-K4 
> driving it?
> 
> Jim / K7TXA
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Re: [Elecraft] KPA500/KAT500 with Yaesu FT-710 Transciever

[john]

You could just connect the RF cables and the relay cable and let the KPA/KAT
detect and automatically change bands. It will work very well this way.

John KK9A


William Santos KN6UDK wrote:

Hello gang,

I'm considering purchase of a KPA500/KAT500 combo to use with my FT-710
Transciever.

Under the "Cables for non-Elecraft Transceivers" section of the KPA500
Elecraft web page, the FT-710 is not listed.

1. What cables do I need for a KPA500/KAT500 combo interfaced with a Yaesu
FT-710 Transciever?

2. Does anyone out there use this configuration? How do you like it? Any
quirks, problems, workarounds?

Thanks and 73,

Bill
KN6UDK

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Re: [Elecraft] KPA500-KAT500 Combo For Sale.

[Mike Dodd]

On 3/2/2023 12:14 PM, Ramon Batista wrote:

Prefer Local Pick-Up Or Meet Up To 100 Miles


QTH?


My QRZ Information Is
Up To Date


And your call sign is??

--- Mike N4CF

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Re: [Elecraft] KPA500 failure

[davidg3una]

Lyn

Just a thought: the rig has a remote on/off facility and you may be getting
extraneous signals into that port.  I know nothing more, but it may give you
a clue where to start looking.  

73 David G3UNA

-Original Message-
From: elecraft-boun...@mailman.qth.net  On
Behalf Of Lyn Norstad
Sent: 09 February 2023 15:57
To: Elecraft@mailman.qth.net
Subject: Re: [Elecraft] KPA500 failure

Here's another twist that makes me thing it could be a PS issue.

Early this morning, I was hunting down 3Y0J on 10m FT8 (very strong signal
here).  WSJT-X was in F/H and S/P mode.  I stepped out of the shack for a
few minutes, and when I came back the KAP500 was powered ON, in Standby mode
with the Fault LED lit up.  It had been powered Off with the front panel
switch since yesterday (the rear panel switch was ON as usual).

How is that possible?

Thx,
Lyn

-Original Message-
From: elecraft-boun...@mailman.qth.net
[mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Lyn Norstad
Sent: Wednesday, February 08, 2023 4:00 PM
To: Elecraft@mailman.qth.net
Subject: [Elecraft] KPA500 failure

A couple days ago, I stepped out of the shack for a few minutes and upon
returning found the KPA500 had shut down.  I didn’t note any brief power
outage, and I’m quite sure it was “ON” when I stepped away.

 

It has been a little quirky in keying since that time.  Yesterday it gave
off a funny smell and the Power and SWR LEDs were jumping up and down for no
apparent reason. The  display screen jumps to frequency readout when I key
the exciter, no matter what it is set for.

 

The KAT500 seems to be working normally with the amp either OFF or in
Standby.

 

I did a total power reset and reloaded the current firmware (v01.54), but no
change.

 

I have not pulled it apart yet, but I seem to remember these being the
symptoms discussed some time ago that required an LPF rebuild.  Somewhere
along the line, Elecraft switched to a SM board and that’s when the trouble
started.

 

So my question … besides asking for general advice … is if anyone knows the
serial number when Elecraft made that change.  My KPA500 is s/n 03835.

 

Thanks!

 

73

Lyn, WØLEN

 

 

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Re: [Elecraft] KPA500 failure

[Lyn Norstad]

Here's another twist that makes me thing it could be a PS issue.

Early this morning, I was hunting down 3Y0J on 10m FT8 (very strong signal
here).  WSJT-X was in F/H and S/P mode.  I stepped out of the shack for a
few minutes, and when I came back the KAP500 was powered ON, in Standby mode
with the Fault LED lit up.  It had been powered Off with the front panel
switch since yesterday (the rear panel switch was ON as usual).

How is that possible?

Thx,
Lyn

-Original Message-
From: elecraft-boun...@mailman.qth.net
[mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Lyn Norstad
Sent: Wednesday, February 08, 2023 4:00 PM
To: Elecraft@mailman.qth.net
Subject: [Elecraft] KPA500 failure

A couple days ago, I stepped out of the shack for a few minutes and upon
returning found the KPA500 had shut down.  I didn’t note any brief power
outage, and I’m quite sure it was “ON” when I stepped away.

 

It has been a little quirky in keying since that time.  Yesterday it gave
off a funny smell and the Power and SWR LEDs were jumping up and down for no
apparent reason. The  display screen jumps to frequency readout when I key
the exciter, no matter what it is set for.

 

The KAT500 seems to be working normally with the amp either OFF or in
Standby.

 

I did a total power reset and reloaded the current firmware (v01.54), but no
change.

 

I have not pulled it apart yet, but I seem to remember these being the
symptoms discussed some time ago that required an LPF rebuild.  Somewhere
along the line, Elecraft switched to a SM board and that’s when the trouble
started.

 

So my question … besides asking for general advice … is if anyone knows the
serial number when Elecraft made that change.  My KPA500 is s/n 03835.

 

Thanks!

 

73

Lyn, WØLEN

 

 

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Re: [Elecraft] KPA500 Also faulting for High SWR inappropriately

[Fred Jensen]

1. "The Problem" is almost never caused by "the worst thing that could 
happen."


2.  Humans will nearly always assume it's "the worst thing that could 
happen."


While learning to fly an airplane many years ago, IP told me, "By far, 
the reason for landing with the gear up is because you abandoned the 
checklist and forgot to put the wheels down.  It's almost never the 
airplane's fault."


73,

Fred ["Skip"] K6DGW
Sparks NV DM09dn
Washoe County

Tom N4LSJ wrote on 1/4/2023 6:31 AM:
I got a KPA500 this summer and it was doing a lot of faulting.  I had 
to "correct" a few things that were just fine at 100 watts.


1: I discovered that a solder joint in the UNUN had gone bad, and 
fixed that.  That solved most of the faults.
2: With still the occasional fault, I looked again and discovered 
there was a spot on one of the windings in my UNUN that had been 
scraped free of enamel.  I applied insulation.
3: After several months of great operation, my receiver had started to 
"cut out" after transmitting.  At first, I thought my rig was going 
kaput, but it was an inline SO-239 barrell that had gotten heated up 
because of no longer being a tight fit. Replacing that cured it.


Moral: It's almost always the antenna system, somewhere.



On 12/30/22 15:20, Jack Brindle via Elecraft wrote:

Amazingly, it is probably not the KPA500.

We have been seeing quite a few inquiries about this. Analysis almost 
always shows an issue in the antenna system caused by high power.


There are a few things at play. When measuring SWR (or better, 
antenna S parameters) at low power, you will get the results of the 
low power measurements. These are usually quite good for determine 
antenna characteristics and generally tell you almost everything 
going on with the antenna. They do not tell you how the antenna 
handles high power.


Antenna system components, including the feed line , connectors, wire 
and so forth, are designed to handle some level of power before they 
will fail in some way.
As an example, spacing of the windings in loading coils matters. Too 
small, and the coil will arc at high power. The same is true with 
connectors, center insulators and the like. Many antennas have 
matching boxes at their feed point to properly match the feed line to 
the antenna. These have a rating, and many are amazingly low.
One popular (and very good) commercial dipole antenna is rated for 
1000 watts ICAS. The specifications later state that the antenna 
should not exceed 500 watts on CW. This is especially important when 
running digital modes such as FT8 which keep power applied to the 
antenna for long periods of time. As power is applied, the components 
will heat and will eventually fail. When they fail, probably not 
catastrophically, they will change the matching characteristics, and 
the amplifier will see a very high reflected power that will cause it 
to protect itself. When the user inspects the components (with power 
off), they will probably not see a problem - unless the component 
failed catastrophically, it will have cooled by then. The problem 
will repeat itself, of course. No measurement taken with an antenna 
analyzer or VNA will show the problem, because they work at very low 
power levels.


When you select an antenna, the ratings must be taken into 
consideration. Manufacturers like to hide the power ratings 
(especially those with built-in matching systems) in order to get 
more sales. If you want to run high power, don’t use a miniature beam 
- they need lots of matching and are almost always designed to run at 
low power. The same is true for compromise wire antennas and those 
that require matching networks at their feed point. Also watch for 
compromise connectors and adapters. Right-angle UHF adapters are 
notorious for arcing. You can’t see it because it is inside the 
connector, but that arcing is probably the cause of a PA Dissipation 
fault in the amplifier. Make sure connections are tight - hand tight 
is not good enough. Use the best connectors you can get. The industry 
standard is Amphenol - they have very high quality standards.


In short, make sure the antenna system you are using is designed to 
handle high power for doing periods of time. If not, it will fail, 
and when you inspect it you will wonder why.


73,
Jack, W6FB

On Dec 30, 2022, at 12:46 PM, marv marvrossphoto.com 
 wrote:


I have pretty much the same symptoms reported by the KPA1500 users 
here.  The higher the frequency the more likely to see a fault.  10M 
is the worst one.  The amp shows a 2:1 SWR and that is running it 
into a tuned KAT500, which shows 1.2:1 and a Daiwa bridge showing 
1.1:1 into the antenna.  It's the same on a dummy load.


I don't understand Bob McGraw's logic as if it does require power, 
my Daiwa is gonna see it.  If I measure the feedline, lightning 
protection and antenna with a network analyzer I will be doing it 
with mili Watts.


Cheers,

Marv
W0PSY




--
This email has been checked for 

Re: [Elecraft] KPA500 Also faulting for High SWR inappropriately

[Tom N4LSJ]

I got a KPA500 this summer and it was doing a lot of faulting.  I had to 
"correct" a few things that were just fine at 100 watts.


1: I discovered that a solder joint in the UNUN had gone bad, and fixed 
that.  That solved most of the faults.
2: With still the occasional fault, I looked again and discovered there 
was a spot on one of the windings in my UNUN that had been scraped free 
of enamel.  I applied insulation.
3: After several months of great operation, my receiver had started to 
"cut out" after transmitting.  At first, I thought my rig was going 
kaput, but it was an inline SO-239 barrell that had gotten heated up 
because of no longer being a tight fit. Replacing that cured it.


Moral: It's almost always the antenna system, somewhere.



On 12/30/22 15:20, Jack Brindle via Elecraft wrote:

Amazingly, it is probably not the KPA500.

We have been seeing quite a few inquiries about this. Analysis almost always 
shows an issue in the antenna system caused by high power.

There are a few things at play. When measuring SWR (or better, antenna S 
parameters) at low power, you will get the results of the low power 
measurements. These are usually quite good for determine antenna 
characteristics and generally tell you almost everything going on with the 
antenna. They do not tell you how the antenna handles high power.

Antenna system components, including the feed line , connectors, wire and so 
forth, are designed to handle some level of power before they will fail in some 
way.
As an example, spacing of the windings in loading coils matters. Too small, and 
the coil will arc at high power. The same is true with connectors, center 
insulators and the like. Many antennas have matching boxes at their feed point 
to properly match the feed line to the antenna. These have a rating, and many 
are amazingly low.
One popular (and very good) commercial dipole antenna is rated for 1000 watts 
ICAS. The specifications later state that the antenna should not exceed 500 
watts on CW. This is especially important when running digital modes such as 
FT8 which keep power applied to the antenna for long periods of time. As power 
is applied, the components will heat and will eventually fail. When they fail, 
probably not catastrophically, they will change the matching characteristics, 
and the amplifier will see a very high reflected power that will cause it to 
protect itself. When the user inspects the components (with power off), they 
will probably not see a problem - unless the component failed catastrophically, 
it will have cooled by then. The problem will repeat itself, of course. No 
measurement taken with an antenna analyzer or VNA will show the problem, 
because they work at very low power levels.

When you select an antenna, the ratings must be taken into consideration. 
Manufacturers like to hide the power ratings (especially those with built-in 
matching systems) in order to get more sales. If you want to run high power, 
don’t use a miniature beam - they need lots of matching and are almost always 
designed to run at low power. The same is true for compromise wire antennas and 
those that require matching networks at their feed point. Also watch for 
compromise connectors and adapters. Right-angle UHF adapters are notorious for 
arcing. You can’t see it because it is inside the connector, but that arcing is 
probably the cause of a PA Dissipation fault in the amplifier. Make sure 
connections are tight - hand tight is not good enough. Use the best connectors 
you can get. The industry standard is Amphenol - they have very high quality 
standards.

In short, make sure the antenna system you are using is designed to handle high 
power for doing periods of time. If not, it will fail, and when you inspect it 
you will wonder why.

73,
Jack, W6FB



On Dec 30, 2022, at 12:46 PM, marv marvrossphoto.com  
wrote:

I have pretty much the same symptoms reported by the KPA1500 users here.  The 
higher the frequency the more likely to see a fault.  10M is the worst one.  
The amp shows a 2:1 SWR and that is running it into a tuned KAT500, which shows 
1.2:1 and a Daiwa bridge showing 1.1:1 into the antenna.  It's the same on a 
dummy load.

I don't understand Bob McGraw's logic as if it does require power, my Daiwa is 
gonna see it.  If I measure the feedline, lightning protection and antenna with 
a network analyzer I will be doing it with mili Watts.

Cheers,

Marv
W0PSY
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Re: [Elecraft] KPA500 Also faulting for High SWR inappropriately

[Jack Brindle via Elecraft]

Amazingly, it is probably not the KPA500. 

We have been seeing quite a few inquiries about this. Analysis almost always 
shows an issue in the antenna system caused by high power.

There are a few things at play. When measuring SWR (or better, antenna S 
parameters) at low power, you will get the results of the low power 
measurements. These are usually quite good for determine antenna 
characteristics and generally tell you almost everything going on with the 
antenna. They do not tell you how the antenna handles high power. 

Antenna system components, including the feed line , connectors, wire and so 
forth, are designed to handle some level of power before they will fail in some 
way.
As an example, spacing of the windings in loading coils matters. Too small, and 
the coil will arc at high power. The same is true with connectors, center 
insulators and the like. Many antennas have matching boxes at their feed point 
to properly match the feed line to the antenna. These have a rating, and many 
are amazingly low. 
One popular (and very good) commercial dipole antenna is rated for 1000 watts 
ICAS. The specifications later state that the antenna should not exceed 500 
watts on CW. This is especially important when running digital modes such as 
FT8 which keep power applied to the antenna for long periods of time. As power 
is applied, the components will heat and will eventually fail. When they fail, 
probably not catastrophically, they will change the matching characteristics, 
and the amplifier will see a very high reflected power that will cause it to 
protect itself. When the user inspects the components (with power off), they 
will probably not see a problem - unless the component failed catastrophically, 
it will have cooled by then. The problem will repeat itself, of course. No 
measurement taken with an antenna analyzer or VNA will show the problem, 
because they work at very low power levels.

When you select an antenna, the ratings must be taken into consideration. 
Manufacturers like to hide the power ratings (especially those with built-in 
matching systems) in order to get more sales. If you want to run high power, 
don’t use a miniature beam - they need lots of matching and are almost always 
designed to run at low power. The same is true for compromise wire antennas and 
those that require matching networks at their feed point. Also watch for 
compromise connectors and adapters. Right-angle UHF adapters are notorious for 
arcing. You can’t see it because it is inside the connector, but that arcing is 
probably the cause of a PA Dissipation fault in the amplifier. Make sure 
connections are tight - hand tight is not good enough. Use the best connectors 
you can get. The industry standard is Amphenol - they have very high quality 
standards.

In short, make sure the antenna system you are using is designed to handle high 
power for doing periods of time. If not, it will fail, and when you inspect it 
you will wonder why.

73,
Jack, W6FB


> On Dec 30, 2022, at 12:46 PM, marv marvrossphoto.com  
> wrote:
> 
> I have pretty much the same symptoms reported by the KPA1500 users here.  The 
> higher the frequency the more likely to see a fault.  10M is the worst one.  
> The amp shows a 2:1 SWR and that is running it into a tuned KAT500, which 
> shows 1.2:1 and a Daiwa bridge showing 1.1:1 into the antenna.  It's the same 
> on a dummy load.
> 
> I don't understand Bob McGraw's logic as if it does require power, my Daiwa 
> is gonna see it.  If I measure the feedline, lightning protection and antenna 
> with a network analyzer I will be doing it with mili Watts.
> 
> Cheers,
> 
> Marv
> W0PSY
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Re: [Elecraft] KPA500 App

[Joel Black]

Thanks, Jack. Yeah, I realized what I did after Walter sent the link. I went 
here (https://elecraft.com/pages/kpa1500-kpa500-kat500-remote-software) the 
first time and only saw the Windows files. I thought I had seen them for macOS 
previously but, for the life of me, I couldn’t find them again.

Thanks again.

Joel - W4JBB

> On Dec 14, 2022, at 6:20 PM, Jack Brindle  wrote:
> 
> Joel;
> 
> It’s worth the look. We have most apps for both Windows and Mac. 
> By the way, the KPA500 firmware was developed and is still maintained using a 
> Mac mini, which is a good
> indication as to how important both Windows and macOS are to us.
> 
> Welcome to the Elecraft world; we hope you will enjoy your KPA500/KAT500 pair!
> 
> 73,
> Jack, W6FB
> 
> 
>> On Dec 14, 2022, at 5:06 PM, Joel Black  wrote:
>> 
>> Before I go looking too hard, is there a macOS app for the KPA500 or *just* 
>> the Windows app on the Elecraft site.
>> 
>> If it matters, I’m looking to interface the KPA500/KAT500 combo to a Flex 
>> 6400… Maybe. I’ve not bought the amp or tuner… Yet.
>> 
>> My preferred OS is macOS but I do use Win11 in a VM for Winlink using my 
>> Flex.
>> 
>> Thanks,
>> Joel - W4JBB
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Re: [Elecraft] KPA500 App

[Jack Brindle via Elecraft]

Joel;

It’s worth the look. We have most apps for both Windows and Mac. 
By the way, the KPA500 firmware was developed and is still maintained using a 
Mac mini, which is a good
indication as to how important both Windows and macOS are to us.

Welcome to the Elecraft world; we hope you will enjoy your KPA500/KAT500 pair!

73,
Jack, W6FB


> On Dec 14, 2022, at 5:06 PM, Joel Black  wrote:
> 
> Before I go looking too hard, is there a macOS app for the KPA500 or *just* 
> the Windows app on the Elecraft site.
> 
> If it matters, I’m looking to interface the KPA500/KAT500 combo to a Flex 
> 6400… Maybe. I’ve not bought the amp or tuner… Yet.
> 
> My preferred OS is macOS but I do use Win11 in a VM for Winlink using my Flex.
> 
> Thanks,
> Joel - W4JBB
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Re: [Elecraft] KPA500 App

[Walter Underwood]

It is right here, under “Macintosh”.

https://elecraft.com/pages/kpa500-500-watt-linear-amplifier-firmware-and-utility

wunder
K6WRU
Walter Underwood
CM87wj
http://observer.wunderwood.org/ (my blog)

> On Dec 14, 2022, at 3:06 PM, Joel Black  wrote:
> 
> Before I go looking too hard, is there a macOS app for the KPA500 or *just* 
> the Windows app on the Elecraft site.
> 
> If it matters, I’m looking to interface the KPA500/KAT500 combo to a Flex 
> 6400… Maybe. I’ve not bought the amp or tuner… Yet.
> 
> My preferred OS is macOS but I do use Win11 in a VM for Winlink using my Flex.
> 
> Thanks,
> Joel - W4JBB
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Re: [Elecraft] KPA500 transformer removal

[Mike Maloney]

 Am guessing that toroid transformer is 70% or more of total KPA mass?
Has anyone put it on a scale and remembed its weight? 
Be sure to seat and torque bolt properly when putting it back in.  
Mike AC5P
On Tuesday, November 22, 2022 at 07:50:22 AM CST, Michael Walker 
 wrote:  
 
 Not really.

Just label the wires so you know were to put them when it comes back.

Undo the bolt and pull the big torroid out.  You'll notice the KPA500 is a
lot lighter now.  :)

73, mike va3mw

On Tue, Nov 22, 2022 at 6:42 AM  wrote:

> I am sending my KPA500 to Watsonville for service. The shipping
> instructions
> say to "remove the transformer unless otherwise instructed."
>
> Are there any instructions for transformer removal? I've looked at the
> assembly instructions and it seems straightforward.
>
> Are there any potential pitfalls that I should be aware of?
>
>
>
> Dave N1IX
>
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Re: [Elecraft] KPA500 transformer removal

[Michael Walker]

Not really.

Just label the wires so you know were to put them when it comes back.

Undo the bolt and pull the big torroid out.  You'll notice the KPA500 is a
lot lighter now.  :)

73, mike va3mw

On Tue, Nov 22, 2022 at 6:42 AM  wrote:

> I am sending my KPA500 to Watsonville for service. The shipping
> instructions
> say to "remove the transformer unless otherwise instructed."
>
> Are there any instructions for transformer removal? I've looked at the
> assembly instructions and it seems straightforward.
>
> Are there any potential pitfalls that I should be aware of?
>
>
>
> Dave N1IX
>
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Re: [Elecraft] KPA500 Voltage?

[Ed Cole]

PS:  Only the mains line is aluminum and connections treated with 
antioxidant paste.  All new wiring in the new hamshack is copper (12-2 
for 120vac and 10-3 for 240vac).


The 3000w Meanwell 50v PS is served with a short 10-3 line to a 30A 
twist-lock receptacle in a floor mounted utility box with three foot 8-3 
jumper to the PS (All copper).  Max load is 12.5A; fused at 15A. 
Meanwell has internal overload and overtemp auto shutdown.


Main thermostat (3000w) is programmable, so heat load will only be 
highest when the area is occupied.  The workshop has manual thermostat 
which can be turned off when shop not in use (dividing wall is insulated 
between hamshack and workshop).


The building will have a monitored (24/7) security system with smoke 
monitors.  Monitor service calls police/fire dept if no one answers the 
phone.  Two FD stations within five miles.


I guess I could add thermistors to the mains contacts to alert overtemp. 
 I use such a system on my QRO amp heatsinks to protect the amps 
(auto-overtemp shutdown of B+).


I will monitor initial application of 240vac power to look for problems.
In my college years I was a Electrician assistant for one summer job and 
got a good practical education installing ckts (even 440 industrial).


Thanks for all the comments!

Ed - KL7UW
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Re: [Elecraft] KPA500 Shifting Bands without any change in K3 Frequency

[w1ie]

GM Joe,

It can't be solved. The SSB and/or Data at that AF MARS frequency  is just
slightly below the band pass filter change over to the 5.3 bandpass filter
on the KPA500. That means that when you are on SSB, part of your rf envelope
crosses over to the 5.3 band filter which causes the amp to switch to the
higher bandpass (5.3) and when the rf at the frequency stops, the amp
switches back to the 3.5 bandpass. It is not that noticeable at SSB
operations because most men's vocal range does not stay or reach up high
enough to trigger the switch. On data, however it's a different story. Since
the M101 waveform has a bandwidth of 2.8 KHz, your signal is almost always
going to cross over that "flash point" causing the amp to go from OPER to
STBY and vice-a-versa. There is a slight delay in the switching because of
what I believe, are the high and low thresh holds of the filter frequency
change point. There is also some delay in the changeover since again, what I
believe is a hardware/software operation which says "I know you have change
to a higher/or lower frequency, but I am not going to change to the correct
band pass filter until - say 100 milliseconds later, because you might not
have meant to do this". That's just a rhetorical guess on my part.

I brought this problem up with Elecraft some time ago so they know about the
MARS Radio. Elecraft said there could be a software solution to move the
trip points up a little bit. There were not, however, going to do it
because the demand for the change is too low, there would be a lot of effort
to test the modification and finally, it would be a another parallel version
of the product to maintain.

Hope this helps

With best regards,

Jerry, W1IE, AFA3GK 

-Original Message-
From: elecraft-boun...@mailman.qth.net  On
Behalf Of Joe Rogers
Sent: Monday, November 14, 2022 21:00 PM
To: elecraft@mailman.qth.net
Subject: [Elecraft] KPA500 Shifting Bands without any change in K3 Frequency

I am operating the KPA500 KAT500 power combo with the K3.  The combination
works great and normally makes frequency and antenna changes really simple.
I operate on MARS frequencies and normally all works just fine outside of
all the amateur bands with the KPA500/KAT500/K3 there is, however, one
frequency where there is an issue.
When transmitting at about 4.5 MHz using SSB or digital modes, using the
KPA500/KAT500/K3 combination, the band indication shoes the KPA500
spuriously shifting back and forth between 3.5 and 5.3 MHz bands.  This also
affects the amplifier output power. I can also hear what sounds like
contact/relay cycling.   This makes the combo unusable on this frequency.
How can I resolve this problem so that the KPA500 is usable on this
frequency?
73
Joe AJ1Y
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-Original Message-
From: elecraft-boun...@mailman.qth.net  On
Behalf Of Joe Rogers
Sent: Monday, November 14, 2022 21:00 PM
To: elecraft@mailman.qth.net
Subject: [Elecraft] KPA500 Shifting Bands without any change in K3 Frequency

I am operating the KPA500 KAT500 power combo with the K3.  The combination
works great and normally makes frequency and antenna changes really simple.
I operate on MARS frequencies and normally all works just fine outside of
all the amateur bands with the KPA500/KAT500/K3 there is, however, one
frequency where there is an issue.
When transmitting at about 4.5 MHz using SSB or digital modes, using the
KPA500/KAT500/K3 combination, the band indication shoes the KPA500
spuriously shifting back and forth between 3.5 and 5.3 MHz bands.  This also
affects the amplifier output power. I can also hear what sounds like
contact/relay cycling.   This makes the combo unusable on this frequency.
How can I resolve this problem so that the KPA500 is usable on this
frequency?
73
Joe AJ1Y
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Re: [Elecraft] KPA500 Shifting Bands without any change in K3 Frequency

[Rick NK7I]

Have you tried putting the KAT500 into MAN mode (not bypass or AUTO)?  
Once trained for bands (memory loaded), MAN is the best way to use the 
tuner.  It'll recall the tuning combination but won't go into auto-retune.


73,
Rick nk7i


On 11/14/2022 6:00 PM, Joe Rogers wrote:

I am operating the KPA500 KAT500 power combo with the K3.  The combination 
works great and normally makes frequency and antenna changes really simple.  I 
operate on MARS frequencies and normally all works just fine outside of all the 
amateur bands with the KPA500/KAT500/K3 there is, however, one frequency where 
there is an issue.
When transmitting at about 4.5 MHz using SSB or digital modes, using the 
KPA500/KAT500/K3 combination, the band indication shoes the KPA500 spuriously 
shifting back and forth between 3.5 and 5.3 MHz bands.  This also affects the 
amplifier output power. I can also hear what sounds like contact/relay cycling. 
  This makes the combo unusable on this frequency.
How can I resolve this problem so that the KPA500 is usable on this frequency?
73
Joe AJ1Y
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Re: [Elecraft] KPA500 Voltage?

[Lyn Norstad]

It's all Cu now.  They just replaced all the underground cables in our
subdivision.  Big stuff.  200A service is the residential standard these
days (we had 400A at the office).

The more expensive it is, the better they like it since the utility rates
guarantee them a fixed percentage of return on their capital investments.

73
Lyn, WØLEN


-Original Message-
From: elecraft-boun...@mailman.qth.net
[mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Jim Brown
Sent: Monday, November 14, 2022 5:20 PM
To: elecraft@mailman.qth.net
Subject: Re: [Elecraft] KPA500 Voltage?

On 11/14/2022 2:08 PM, Lyn Norstad wrote:
> Aluminum does not meet any current (pun by chance ...) building codes
around
> here.

I don't know what Chicago Codes are like now, but Comm Ed pulled Al 
conductors to my meter when I requested 100A service, and they refused 
to pull Cu. This would have been around 1987-90.

73, Jim K9YC


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Re: [Elecraft] KPA500 Voltage?

[Jim Brown]

On 11/14/2022 2:08 PM, Lyn Norstad wrote:

Aluminum does not meet any current (pun by chance ...) building codes around
here.


I don't know what Chicago Codes are like now, but Comm Ed pulled Al 
conductors to my meter when I requested 100A service, and they refused 
to pull Cu. This would have been around 1987-90.


73, Jim K9YC


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Re: [Elecraft] KPA500 Voltage?

[David Gilbert]

Yes ... both.  Go look for yourself.

Flexible cords like line cords are almost never aluminum ... I assume 
because line cords use fine stranded wires and if I'm not mistaken 
copper is more ductile than aluminum.


Dave   AB7E



On 11/14/2022 3:42 PM, Lou Mecseri wrote:

BUT NOT BOTH.

How about line cords?"

Lou KE1F

On 11/14/2022 22:32, David Gilbert wrote:



There is absolutely nothing inherently wrong with aluminum wire, and 
it is typically what is used for very large gauge wire ... even for 
the utility entrance in my location.  I would bet that if you look 
closely at your breaker box you will see the same for the main feed 
coming in unless you have a very lowly rated box for current.  I 
don't think you can even find , for example, 4/0 wire in copper at 
places like Home Depot or Lowes.


The historical problem associated with aluminum wire was the material 
used for connections at the sockets and other places. That has all 
been changed long ago and if you look closely at many electrical 
fixtures and buss bars you will see that the contacts are stamped to 
be rated for either copper or aluminum.


Dave   AB7E



On 11/14/2022 3:08 PM, Lyn Norstad wrote:

Ed -

I cringe when I think of aluminum wiring.  I know it's currently 
about half
the price of copper, but a townhouse I lived in from 1979-1982 in 
Chicago

caught fire because of aluminum wiring and copper outlets.  In fact,
statistics show that 50% of home fires are due to aluminum wiring.

Aluminum does not meet any current (pun by chance ...) building 
codes around

here.  It's all copper. Has been for at least 40 years.

If you're stuck with aluminum (and it's legal??), be sure to 
liberally apply

antioxidant where needed.

73
Lyn, WØLEN




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Re: [Elecraft] KPA500 Voltage?

[Rick NK7I]

Aluminum was legal at one point, as I recall it was the 80's (copper 
prices were obscene).  It was an expensive mistake to allow aluminum wiring.


I attended some fires as a result of aluminum wire (career firefighter, 
eventually Captain).  My suspicion was that as switches and plugs were 
used, aluminum tolerated the small flexing less than copper (which 
basically self heals, molds to the connection being softer) and as it is 
exposed to air, a layer of aluminum oxide is produced (wrapping the 
internal content ) creating higher resistance.


Over time the resistance and small flexes caused arcing, that gets to a 
point that it heats; causing the excitement.


I don't have the chemistry or metallurigc background to confirm this; 
but this was the result of the cause investigation..


Adding a copper pigtail is a practical solution (cheaper than replacing 
all the wire).  Aluminum wire is not used by me, anywhere, just like the 
backstab plugs and switches (if you can't bind them down; don't use 
them).  I have seen the harm that can result and don't want to lose my 
house and possessions as I've seen others lose.


In the cost of a house or shack, copper; the small increase in cost 
reaps major benefits (and aluminum is no longer legal for new 
construction, at least when I retired).


73,
Rick nk7i


On 11/14/2022 2:25 PM, Fred Jensen wrote:
When my younger brother was finally out of the house for good, Mom and 
Dad bought a double-wide, sold the house in So. Central LAX, and moved 
south into a "Mobile Estates Park" in Costa Mesa.  The wiring was Al.  
About 3 years later, they had a problem in one of the outlets that 
involved a small amount of smoke.  That wasn't a serious incident, but 
Dad had to go around to each of the switches and outlets and put Cu 
pigtails on the Al wires to connect to the devices.  I never got a 
clear story about what caused the original problem or why this would 
fix it.  But, I'm really wary of Al wiring in house in which we sleep.


73,

Fred ["Skip"] K6DGW
Sparks NV DM09dn
Washoe County

Lyn Norstad wrote on 11/14/2022 2:08 PM:

Ed -

I cringe when I think of aluminum wiring.  I know it's currently 
about half
the price of copper, but a townhouse I lived in from 1979-1982 in 
Chicago

caught fire because of aluminum wiring and copper outlets.  In fact,
statistics show that 50% of home fires are due to aluminum wiring.

Aluminum does not meet any current (pun by chance ...) building codes 
around

here.  It's all copper. Has been for at least 40 years.

If you're stuck with aluminum (and it's legal??), be sure to 
liberally apply

antioxidant where needed.

73
Lyn, WØLEN






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Re: [Elecraft] KPA500 Voltage?

[Lou Mecseri]

BUT NOT BOTH.

How about line cords?"

Lou KE1F

On 11/14/2022 22:32, David Gilbert wrote:



There is absolutely nothing inherently wrong with aluminum wire, and 
it is typically what is used for very large gauge wire ... even for 
the utility entrance in my location.  I would bet that if you look 
closely at your breaker box you will see the same for the main feed 
coming in unless you have a very lowly rated box for current.  I don't 
think you can even find , for example, 4/0 wire in copper at places 
like Home Depot or Lowes.


The historical problem associated with aluminum wire was the material 
used for connections at the sockets and other places. That has all 
been changed long ago and if you look closely at many electrical 
fixtures and buss bars you will see that the contacts are stamped to 
be rated for either copper or aluminum.


Dave   AB7E



On 11/14/2022 3:08 PM, Lyn Norstad wrote:

Ed -

I cringe when I think of aluminum wiring.  I know it's currently 
about half
the price of copper, but a townhouse I lived in from 1979-1982 in 
Chicago

caught fire because of aluminum wiring and copper outlets.  In fact,
statistics show that 50% of home fires are due to aluminum wiring.

Aluminum does not meet any current (pun by chance ...) building codes 
around

here.  It's all copper. Has been for at least 40 years.

If you're stuck with aluminum (and it's legal??), be sure to 
liberally apply

antioxidant where needed.

73
Lyn, WØLEN




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Re: [Elecraft] KPA500 Voltage?

[Lou Mecseri]

Aluminum wiring is "penny wise and pound foolish".
Coming from a retired Fire Investigator.
Good Luck and 73, Lou KE1F


On 11/14/2022 22:08, Lyn Norstad wrote:

Ed -

I cringe when I think of aluminum wiring.  I know it's currently about half
the price of copper, but a townhouse I lived in from 1979-1982 in Chicago
caught fire because of aluminum wiring and copper outlets.  In fact,
statistics show that 50% of home fires are due to aluminum wiring.

Aluminum does not meet any current (pun by chance ...) building codes around
here.  It's all copper. Has been for at least 40 years.

If you're stuck with aluminum (and it's legal??), be sure to liberally apply
antioxidant where needed.

73
Lyn, WØLEN


-Original Message-
From: elecraft-boun...@mailman.qth.net
[mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Ed Cole
Sent: Monday, November 14, 2022 3:43 PM
To: elecraft@mailman.qth.net
Subject: Re: [Elecraft] KPA500 Voltage?

On the general subject of house wiring, loads, and resulting voltage:

I am wiring my new hamshack with 240vac mains extension from the house.
I selected three No. 2 awg aluminum lines (copper not commonly used
these days).  These are approx 1/4-inch diameter.

That is rated for 90A (in general).  Resistance is 0.318 ohms/1000-feet
so my 120-foot run has 0.0382 ohms.  At 50A this results in a voltage
drop of 1.9v.  My service voltage is 243VAC.

Estimation of max load at the new hamshack/workshop calculates as 36.5A.
   Maximum will likely never exist as not everything will be activated
simultaneously, but good design is for max load.

Largest load is electric baseboard heat (4000w); 50v PS is next (3000w).
All my QRO amps are LDMOS and run about 2500w dc-input.  I use three of
these switching PS, but only one at a time.

Info on my website: www.kl7uw.com

73, Ed - KL7UW

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Re: [Elecraft] KPA500 Voltage?

[David Gilbert]

There is absolutely nothing inherently wrong with aluminum wire, and it 
is typically what is used for very large gauge wire ... even for the 
utility entrance in my location.  I would bet that if you look closely 
at your breaker box you will see the same for the main feed coming in 
unless you have a very lowly rated box for current.  I don't think you 
can even find , for example, 4/0 wire in copper at places like Home 
Depot or Lowes.


The historical problem associated with aluminum wire was the material 
used for connections at the sockets and other places.  That has all been 
changed long ago and if you look closely at many electrical fixtures and 
buss bars you will see that the contacts are stamped to be rated for 
either copper or aluminum.


Dave   AB7E



On 11/14/2022 3:08 PM, Lyn Norstad wrote:

Ed -

I cringe when I think of aluminum wiring.  I know it's currently about half
the price of copper, but a townhouse I lived in from 1979-1982 in Chicago
caught fire because of aluminum wiring and copper outlets.  In fact,
statistics show that 50% of home fires are due to aluminum wiring.

Aluminum does not meet any current (pun by chance ...) building codes around
here.  It's all copper. Has been for at least 40 years.

If you're stuck with aluminum (and it's legal??), be sure to liberally apply
antioxidant where needed.

73
Lyn, WØLEN




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Re: [Elecraft] KPA500 Voltage?

[Fred Jensen]

When my younger brother was finally out of the house for good, Mom and 
Dad bought a double-wide, sold the house in So. Central LAX, and moved 
south into a "Mobile Estates Park" in Costa Mesa.  The wiring was Al.  
About 3 years later, they had a problem in one of the outlets that 
involved a small amount of smoke.  That wasn't a serious incident, but 
Dad had to go around to each of the switches and outlets and put Cu 
pigtails on the Al wires to connect to the devices.  I never got a clear 
story about what caused the original problem or why this would fix it.  
But, I'm really wary of Al wiring in house in which we sleep.


73,

Fred ["Skip"] K6DGW
Sparks NV DM09dn
Washoe County

Lyn Norstad wrote on 11/14/2022 2:08 PM:

Ed -

I cringe when I think of aluminum wiring.  I know it's currently about half
the price of copper, but a townhouse I lived in from 1979-1982 in Chicago
caught fire because of aluminum wiring and copper outlets.  In fact,
statistics show that 50% of home fires are due to aluminum wiring.

Aluminum does not meet any current (pun by chance ...) building codes around
here.  It's all copper. Has been for at least 40 years.

If you're stuck with aluminum (and it's legal??), be sure to liberally apply
antioxidant where needed.

73
Lyn, WØLEN





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Re: [Elecraft] KPA500 Voltage?

[Jim Brown]

On 11/14/2022 1:43 PM, Ed Cole wrote:
That is rated for 90A (in general).  Resistance is 0.318 ohms/1000-feet 
so my 120-foot run has 0.0382 ohms.  At 50A this results in a voltage 
drop of 1.9v.  My service voltage is 243VAC.


It's important to realize that current on AC mains is FAR from being a 
sine wave. This has been true for at least 30 years, as loads have been 
strongly dominated by switch-mode power supplies in almost every piece 
of equipment wiring into or plugged into, the system, and square-wave 
modulated controllers for nearly all large loads, like motors and 
heating devices. Current flows in pulses, usually short ones, that 
recharge the input capacitors of associated power supplies.


The result of this is that both IR drop and the resulting heating are at 
least one-third greater than predicted by Ohm's Law applied to a sine 
wave. It is, therefore, very good engineering practice to oversize 
conductors, as you have done! Before we moved into the home we bought in 
NorCal, I had the outbuilding housing my shack rewired, and even though 
the runs from the panelboard are pretty short, had #10 pulled in for the 
20A-240V circuit. Since I will never have more than one amp on at a 
time, I felt that 20A was sufficient. All of the 120V circuits are 20A, 
wired with #12, not oversized, since the only heavy load, 1 12A space 
heater, has its own circuit.


73, Jim K9YC

73, Jim K9YC
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Re: [Elecraft] KPA500 Voltage?

[Lyn Norstad]

Ed -

I cringe when I think of aluminum wiring.  I know it's currently about half
the price of copper, but a townhouse I lived in from 1979-1982 in Chicago
caught fire because of aluminum wiring and copper outlets.  In fact,
statistics show that 50% of home fires are due to aluminum wiring.

Aluminum does not meet any current (pun by chance ...) building codes around
here.  It's all copper. Has been for at least 40 years.

If you're stuck with aluminum (and it's legal??), be sure to liberally apply
antioxidant where needed.

73
Lyn, WØLEN


-Original Message-
From: elecraft-boun...@mailman.qth.net
[mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Ed Cole
Sent: Monday, November 14, 2022 3:43 PM
To: elecraft@mailman.qth.net
Subject: Re: [Elecraft] KPA500 Voltage?

On the general subject of house wiring, loads, and resulting voltage:

I am wiring my new hamshack with 240vac mains extension from the house.
I selected three No. 2 awg aluminum lines (copper not commonly used 
these days).  These are approx 1/4-inch diameter.

That is rated for 90A (in general).  Resistance is 0.318 ohms/1000-feet 
so my 120-foot run has 0.0382 ohms.  At 50A this results in a voltage 
drop of 1.9v.  My service voltage is 243VAC.

Estimation of max load at the new hamshack/workshop calculates as 36.5A. 
  Maximum will likely never exist as not everything will be activated 
simultaneously, but good design is for max load.

Largest load is electric baseboard heat (4000w); 50v PS is next (3000w).
All my QRO amps are LDMOS and run about 2500w dc-input.  I use three of 
these switching PS, but only one at a time.

Info on my website: www.kl7uw.com

73, Ed - KL7UW

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Re: [Elecraft] KPA500 Voltage?

[Ed Cole]

On the general subject of house wiring, loads, and resulting voltage:

I am wiring my new hamshack with 240vac mains extension from the house.
I selected three No. 2 awg aluminum lines (copper not commonly used 
these days).  These are approx 1/4-inch diameter.


That is rated for 90A (in general).  Resistance is 0.318 ohms/1000-feet 
so my 120-foot run has 0.0382 ohms.  At 50A this results in a voltage 
drop of 1.9v.  My service voltage is 243VAC.


Estimation of max load at the new hamshack/workshop calculates as 36.5A. 
 Maximum will likely never exist as not everything will be activated 
simultaneously, but good design is for max load.


Largest load is electric baseboard heat (4000w); 50v PS is next (3000w).
All my QRO amps are LDMOS and run about 2500w dc-input.  I use three of 
these switching PS, but only one at a time.


Info on my website: www.kl7uw.com

73, Ed - KL7UW

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Re: [Elecraft] KPA500 Voltage?

[Lyn Norstad]

Jim -

Of course, that's what the various taps are for.  But at the higher setting,
although the voltage was within the published "acceptable" range, 2
components in the power supply failed.

This was the second time it had been back for service - the first time they
discovered missing components (it was factory built).

I'm not going to argue with the Mothership.  It has been flawless since the
second service trip.  If I'm down a couple watts (not at all sure that's the
case), it's better than being down a couple Franklins.

73
Lyn, WØLEN

-Original Message-
From: elecraft-boun...@mailman.qth.net
[mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Jim Brown
Sent: Monday, November 14, 2022 12:37 PM
To: elecraft@mailman.qth.net
Subject: Re: [Elecraft] KPA500 Voltage?

On 11/14/2022 6:38 AM, Lyn Norstad wrote:
> I had mine set up, as Rick suggests - but when it was in for service, they
dropped it back a notch saying it was too high.

That's the difference between their mains wiring and yours. I'd stick 
with what is highest, within range, at your QTH.

73, Jim K9YC
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Re: [Elecraft] KPA500 Voltage?

[Jim Brown]

On 11/14/2022 9:36 AM, Jon Poland wrote:

My 12 year old house has 200 amp service.  I don't know why.  But since
building it, we have shifted to 90+% LED lighting, high efficiency
dishwasher, fridge, and clothes washer.  My entire lighting load at any
given time is less than 120W.  A smart thermostat reduces AC and furnace
loads.  The 2 largest electrical loads are the clothes dryer and gas
furnace blower.  This house is also better insulated than any home I have
ever owned - also reducing the furnace load (gas and electricity).


What you're missing, Jon, is that IR drop to that outlet that feeds the 
KPA500 is NOT the total load to the home, but primarily the IR drop FROM 
THE PANEL of the circuit that feeds the amp. The feed from the street to 
that panel is usually a small fraction of that.


73, Jim K9YC
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Re: [Elecraft] KPA500 Voltage?

[Jim Brown]

On 11/14/2022 6:38 AM, Lyn Norstad wrote:

I had mine set up, as Rick suggests - but when it was in for service, they 
dropped it back a notch saying it was too high.


That's the difference between their mains wiring and yours. I'd stick 
with what is highest, within range, at your QTH.


73, Jim K9YC
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Re: [Elecraft] KPA500 Voltage?

[Rick NK7I]

:
> Gordon -
>
> I had mine set up, as Rick suggests - but when it was in for
service, they dropped it back a notch saying it was too high.
>
> My readings now agree with yours.
>
> 73
> Lyn, WØLEN
>
>
> -Original Message-
> From:elecraft-boun...@mailman.qth.net
<mailto:from%3aelecraft-boun...@mailman.qth.net>
[mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Rick NK7I
> Sent: Saturday, November 12, 2022 1:03 PM
> To:elecraft@mailman.qth.net <mailto:to%3aelecr...@mailman.qth.net>
> Subject: Re: [Elecraft] KPA500 Voltage?
>
> I'd move it up one tap as long as it does NOT EXCEED 85V at receive.
>
> Higher voltage not only gives you better output but also
cleaner.  That
> matters too.
>
> 73,
> Rick nk7i
>
>
> On 11/12/2022 10:25 AM, Gordon LaPoint wrote:
>> My KPA500 is showing 57-58 VDC at 450-500 watts out, and 71-72
VDC on rx.
>>
>> Is this normal or should I move up one tap?
>>
>> Thanks,
>>
>> Gordon - N1MGO
>>
>>
>> __
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Re: [Elecraft] KPA500 Voltage?

[Jon Poland]

I disagree with Rick.  It is true that modern houses have more electric
capacity.  But as homeowners shift to more efficient appliances and
lighting, electric loads (and bills) are consistently dropping.  The one
trend that counters that though is that modern homes (at least in the US)
are consistently larger than their older counterparts and require more
energy to keep comfortable.  That trend does not explain voltage drops
though.

My 12 year old house has 200 amp service.  I don't know why.  But since
building it, we have shifted to 90+% LED lighting, high efficiency
dishwasher, fridge, and clothes washer.  My entire lighting load at any
given time is less than 120W.  A smart thermostat reduces AC and furnace
loads.  The 2 largest electrical loads are the clothes dryer and gas
furnace blower.  This house is also better insulated than any home I have
ever owned - also reducing the furnace load (gas and electricity).

Curiously, the next largest load in many homes are the TV's turned on in
every bedroom... (But their heat reduces the amount of time the furnace
needs to run.)

Of course, if you have an electric car charger the picture changes
drastically...  But that is still a small percentage of US homes today.

jon  N0WL

On Mon, Nov 14, 2022 at 11:10 AM Rick Bates, NK7I 
wrote:

> Too high at THEIR location.
>
> Power company feeds, vary (not a lot but their load changes, they adjust).
>
> House wiring varies and other devices on that circuit can cause other
> variations too.  Older homes (1950's and older) often have less capacity
> than newer homes (didn't need it then).  Today we use a LOT more energy
> than then; some house circuits are no longer 'adequate' (causing fires
> in some cases because folks abuse the wiring in ignorance).
>
> Part of station set up and operations, is knowing what the circuit(s) of
> the house wiring, is connected to besides the station.  Fridge, washer,
> HVAC, electric oven shared with the station?
>
> If you need one more tap to get within the right voltage window, use one
> more tap to achieve that.  If you change circuits, remeasure.  And if on
> the same circuit, maybe don't run the washing machine or oven at the
> same time as the amp. ;-)
>
> 73,
> Rick nk7i
>
>
> On 11/14/2022 6:38 AM, Lyn Norstad wrote:
> > Gordon -
> >
> > I had mine set up, as Rick suggests - but when it was in for service,
> they dropped it back a notch saying it was too high.
> >
> > My readings now agree with yours.
> >
> > 73
> > Lyn, WØLEN
> >
> >
> > -Original Message-
> > From:elecraft-boun...@mailman.qth.net  [mailto:
> elecraft-boun...@mailman.qth.net] On Behalf Of Rick NK7I
> > Sent: Saturday, November 12, 2022 1:03 PM
> > To:elecraft@mailman.qth.net
> > Subject: Re: [Elecraft] KPA500 Voltage?
> >
> > I'd move it up one tap as long as it does NOT EXCEED 85V at receive.
> >
> > Higher voltage not only gives you better output but also cleaner.  That
> > matters too.
> >
> > 73,
> > Rick nk7i
> >
> >
> > On 11/12/2022 10:25 AM, Gordon LaPoint wrote:
> >> My KPA500 is showing 57-58 VDC at 450-500 watts out, and 71-72 VDC on
> rx.
> >>
> >> Is this normal or should I move up one tap?
> >>
> >> Thanks,
> >>
> >> Gordon - N1MGO
> >>
> >>
> >> __
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Re: [Elecraft] KPA500 Voltage?

[Rick Bates, NK7I]

Too high at THEIR location.

Power company feeds, vary (not a lot but their load changes, they adjust).

House wiring varies and other devices on that circuit can cause other 
variations too.  Older homes (1950's and older) often have less capacity 
than newer homes (didn't need it then).  Today we use a LOT more energy 
than then; some house circuits are no longer 'adequate' (causing fires 
in some cases because folks abuse the wiring in ignorance).


Part of station set up and operations, is knowing what the circuit(s) of 
the house wiring, is connected to besides the station.  Fridge, washer, 
HVAC, electric oven shared with the station?


If you need one more tap to get within the right voltage window, use one 
more tap to achieve that.  If you change circuits, remeasure.  And if on 
the same circuit, maybe don't run the washing machine or oven at the 
same time as the amp. ;-)


73,
Rick nk7i


On 11/14/2022 6:38 AM, Lyn Norstad wrote:

Gordon -

I had mine set up, as Rick suggests - but when it was in for service, they 
dropped it back a notch saying it was too high.

My readings now agree with yours.

73
Lyn, WØLEN


-Original Message-
From:elecraft-boun...@mailman.qth.net  
[mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Rick NK7I
Sent: Saturday, November 12, 2022 1:03 PM
To:elecraft@mailman.qth.net
Subject: Re: [Elecraft] KPA500 Voltage?

I'd move it up one tap as long as it does NOT EXCEED 85V at receive.

Higher voltage not only gives you better output but also cleaner.  That
matters too.

73,
Rick nk7i


On 11/12/2022 10:25 AM, Gordon LaPoint wrote:

My KPA500 is showing 57-58 VDC at 450-500 watts out, and 71-72 VDC on rx.

Is this normal or should I move up one tap?

Thanks,

Gordon - N1MGO


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Re: [Elecraft] KPA500 Voltage?

[Lyn Norstad]

Gordon -

I had mine set up, as Rick suggests - but when it was in for service, they 
dropped it back a notch saying it was too high.

My readings now agree with yours.

73
Lyn, WØLEN


-Original Message-
From: elecraft-boun...@mailman.qth.net 
[mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Rick NK7I
Sent: Saturday, November 12, 2022 1:03 PM
To: elecraft@mailman.qth.net
Subject: Re: [Elecraft] KPA500 Voltage?

I'd move it up one tap as long as it does NOT EXCEED 85V at receive.

Higher voltage not only gives you better output but also cleaner.  That 
matters too.

73,
Rick nk7i


On 11/12/2022 10:25 AM, Gordon LaPoint wrote:
> My KPA500 is showing 57-58 VDC at 450-500 watts out, and 71-72 VDC on rx.
>
> Is this normal or should I move up one tap?
>
> Thanks,
>
> Gordon - N1MGO
>
>
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Re: [Elecraft] KPA500 Voltage?

[Jim Brown]

On 11/13/2022 10:52 AM, Andy Durbin wrote:

Note that the drop is not related only to power output but is a function of 
total PA input power


It's also a function of IR drop in ALL of the AC wiring between the 
distribution panel and the amp. In North America, building codes call 
for at least #14 for circuits fused at 15A, and #12 for 20A. Copper is 
expensive, so larger sizes are rarely installed.


73, Jim K9YC
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Re: [Elecraft] KPA500 Voltage?

[Rick NK7I]

I'd move it up one tap as long as it does NOT EXCEED 85V at receive.

Higher voltage not only gives you better output but also cleaner.  That 
matters too.


73,
Rick nk7i


On 11/12/2022 10:25 AM, Gordon LaPoint wrote:

My KPA500 is showing 57-58 VDC at 450-500 watts out, and 71-72 VDC on rx.

Is this normal or should I move up one tap?

Thanks,

Gordon - N1MGO


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Re: [Elecraft] KPA500 Blank Display

[Lyn Norstad]

Bruce -

I've never experienced that with my KPA500, but it sounds like it might be
either a bad ribbon connector, or a bad component on the front panel circuit
board.  Did you assemble it, or was it factory built?

I suggest you talk to Elecraft service.

73
Lyn, WØLEN

-Original Message-
From: elecraft-boun...@mailman.qth.net
[mailto:elecraft-boun...@mailman.qth.net] On Behalf Of bruce ault
Sent: Saturday, October 15, 2022 3:54 PM
To: elecraft@mailman.qth.net
Subject: [Elecraft] KPA500 Blank Display

I'm curious if any others have seen this...

Yesterday I turned on the amp and only the bottom half of the text was
shown on the display.
This slowly faded away leaving just the backlight on,The band switches
were inoperable as
well.   All else worked correctly.

After 20 minutes the display suddenly came back to life and all was well.

After sitting all night the same thing occurred  this morning...blank
display,  et al.   Several
minutes later it was ok.

Any clues?   NOTE:  This is a NEW amp 1 week old.

TNX Bruce  3W3B

-- 
Bruce E. Ault
  XW4XR - 3W3B
Vientiane, LAOS - Da Nang, VIETNAM

 VIETNAM Cell:  +84855287953
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Re: [Elecraft] KPA500 No Output on 6m

[Jim Clymer]

Hi Dave,
More information would be helpful. Are you seeing your radio's output thru
the KPA500 (and on the meters) with the amp in bypass mode? Is the radio's
PTT properly keying the amp? Etc.
Jim - WS6X

On Sun, Sep 4, 2022, 11:35 AM dave ingebright  wrote:

> Bought and assembled a KPA500 kit in 2018. No output on 6m!! I've used it
> on 10-80 and love the performance. Never checked six until I became
> interested in six this summer. Put up a 3 ele yagi and its good
> barefoot/good match but no output on six using the KPA...
> Any ideas? Here's a link to my assembly picts:
> https://www.valhallatreefarm.com/WB7ELY/kpa500/kpa500.htm
> 73,
> Dave WB7ELY
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Re: [Elecraft] KPA500 Parts

[Lyle Johnson]

7.5V

It is not there to regulate, but to limit in case of something bad
happening, while allowing the gate of the FET to get the full control
voltage for T/R switching.  The zener normally is not conducting.

73,

Lyle KK7P

On Wed, Aug 17, 2022 at 12:08 PM RALPH TURK  wrote:

> The real question is/was what value of zener.
>
> > On 08/17/2022 9:45 AM Andy Durbin  wrote:
> >
> >
> > "The latest revision of the schematic for the KPA500 TR Switch shows a
> Zener diode at the gate of Q4 in place of R3, the 100K resistor previously."
> >
> > What is the latest revision?  I have Rev D which is later than any I
> have found on-line but it shows R3 not a Zener.
> >
> > Andy, k3wyc
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Re: [Elecraft] KPA500 Parts

[RALPH TURK]

The real question is/was what value of zener.

> On 08/17/2022 9:45 AM Andy Durbin  wrote:
> 
>  
> "The latest revision of the schematic for the KPA500 TR Switch shows a Zener 
> diode at the gate of Q4 in place of R3, the 100K resistor previously."
> 
> What is the latest revision?  I have Rev D which is later than any I have 
> found on-line but it shows R3 not a Zener.
> 
> Andy, k3wyc
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Re: [Elecraft] KPA500 / 270V ERR

[Andy Durbin]

"He tells me that a failed R16 on the power supply board should have no effect 
on the 60V supply, ."

No, of course it won't.  It will only prevent 270 V being produced if 60 V is 
present.   The amplifier is heavy and will be expensive to ship.  Why not 
diagnose the problem and just fix what has failed?

You have already determined that mains voltage is reaching the low voltage 
supply since you have the display and control panel working.  There really 
isn't much that can kill 60 V if there is input to the main transformer T1.

Failure can probably be isolated to T1, the diode bridge,  the 60 V enable 
relay, and their interconnections (assuming the power supply rails really have 
failed and this isn't a sensing problem).   The problem could be as simple as a 
poor contact on the transformer tap.  The hardest part of the job is removing 
all the screws to gain access to make measurements.

Perhaps the best thing about building a kit is not the small cost saving but 
gaining the confidence to open it up if needed.

Andy, k3wyc
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Re: [Elecraft] KPA500 / 270V ERR

[James Bennett via Elecraft]

Folks - I’ve exchanged email with Rob at Elecraft support. He tells me that a 
failed R16 on the power supply board should have no effect on the 60V supply, 
so I’m opting to NOT rip the amp apart in search of R16. Waiting on Rob to send 
me an RSA and the amp will be off to Watsonville for some first aid. I’ll post 
back here when it is returned and let you know what went south.

73, Jim / K7TXA


> 
>> On Jul 17, 2022, at 4:04 PM, Bruce Forsberg > > wrote:
>> 
>> James I had the 270 V Err message on my KPA500 as well, S/N 3406. It turned
>> out to be R16 on the PS board had opened (S/B 100 ohms). This resistor
>> feeds the voltage multiplier circuit to get to 270V. Don't know if this is
>> your problem or not but does not hurt to check. It is an SMD resistor and I
>> think is accessible from the top.
>> 
>> Bruce, WB6IZG
>> 
>> On Sun, Jul 17, 2022 at 2:51 PM James Bennett via Elecraft <
>> elecraft@mailman.qth.net > wrote:
>> 
>>> Hi - I’ve had my KPA500 serial number 3645 for several years and until
>>> today have had zero problems with it. Previously it was driven by a K3;
>>> currently (until today!) a K4D. Last time I used it, it worked great. Today
>>> I powered it on after having it off for several days and when I went to
>>> Operate mode, I got the dreaded 270V ERR display. When I display HV it
>>> shows “1”. Everything else seems to be OK - band changing works fine,
>>> metering of the power and frequency are OK - just can’t go to Operate mode.
>>> The top cover is on just as tight as it has been for years. Fuses are all
>>> OK.
>>> 
>>> Looked through the archives and did see a few hits, but most were related
>>> to loose top cover or incorrect voltage settings.
>>> 
>>> I’ve fired off an email to Elecraft support earlier today but thought I’d
>>> run it by the owner community too.
>>> 
>>> Suggestions?
>>> 
>>> Jim Bennett / K7TXA
>>> Eagle, ID
>>> 
>>> 
>>> 
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>>> 
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>>> 
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Re: [Elecraft] KPA500 / 270V ERR

[Andy Durbin]

"If you check the schematics, the 270V is made/comes from the power 
supply...BUT the 60V enable relay (feeds the voltage divider and read on the 
front panel) is on the PA board... "

May I suggest that you look at KPA Power Supply Schematic sheet 1 of 2 and 
locate relay K1 (60 V Enable) which is controlled by the interlock switch and 
signal 60 V ENBL.

How is 270 V produced if this relay is open?

How is 270 v produced if 60 V is not present?

I do not think it a coincidence that the OP has lost 270 V and 60 V.  I suspect 
a common cause.

Andy, k3wyc


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Re: [Elecraft] KPA500 / 270V ERR

[Andy Durbin]

"I think it may actually be the other way around... The 60V relay does not 
close if 270V is missing?"

Assume 60 V Enable relay K1 is not closed.  How would 270 V be produced?  The 
secondary winding of T1 is open circuit.

Andy, k3wyc
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Re: [Elecraft] KPA500 / 270V ERR

[Dr. William J. Schmidt]

I think it may actually be the other way around... The 60V relay does not
close if 270V is missing?

-Original Message-
From: elecraft-boun...@mailman.qth.net  On
Behalf Of Andy Durbin
Sent: Sunday, July 17, 2022 6:49 PM
To: elecraft@mailman.qth.net
Subject: [Elecraft] KPA500 / 270V ERR

HV and 270V are separate power supply rails but, if my read of the schematic
is correct, 270 V depends on 60 V being present.  60 V requires the
interlock switch to be closed.

Diagnosing this may require having the top off and the interlock defeated.
Everyone should evaluate their own competence and risk tolerance.

Andy, k3wyc

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Re: [Elecraft] KPA500 / 270V ERR

[Bruce Forsberg]

James I had the 270 V Err message on my KPA500 as well, S/N 3406. It turned
out to be R16 on the PS board had opened (S/B 100 ohms). This resistor
feeds the voltage multiplier circuit to get to 270V. Don't know if this is
your problem or not but does not hurt to check. It is an SMD resistor and I
think is accessible from the top.

Bruce, WB6IZG

On Sun, Jul 17, 2022 at 2:51 PM James Bennett via Elecraft <
elecraft@mailman.qth.net> wrote:

> Hi - I’ve had my KPA500 serial number 3645 for several years and until
> today have had zero problems with it. Previously it was driven by a K3;
> currently (until today!) a K4D. Last time I used it, it worked great. Today
> I powered it on after having it off for several days and when I went to
> Operate mode, I got the dreaded 270V ERR display. When I display HV it
> shows “1”. Everything else seems to be OK - band changing works fine,
> metering of the power and frequency are OK - just can’t go to Operate mode.
> The top cover is on just as tight as it has been for years. Fuses are all
> OK.
>
> Looked through the archives and did see a few hits, but most were related
> to loose top cover or incorrect voltage settings.
>
> I’ve fired off an email to Elecraft support earlier today but thought I’d
> run it by the owner community too.
>
> Suggestions?
>
> Jim Bennett / K7TXA
> Eagle, ID
>
>
>
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Re: [Elecraft] KPA500

[Ian Kahn]

Joseph,

There is no soldering required to assemble the KPA500. If you can use basic
tools (screwdrivers, pliers, etc.), you'll have no issue assembling it. The
assembly manual is also VERY well-written.

You should be fine assembling it yourself.

73 de,

Ian, NV4C

On Fri, Jul 8, 2022, 9:20 AM Josep via Elecraft 
wrote:

> Hi guys,
> I ordered (2 months ago) a KPA500 from Elecraft. I thought I have ordered
> assembled but looks like I have done it wrong and asked for kit.! Now I
> have received all the parts and will have to assemble it myself. I see it
> says no-soldering kit so I assume I just have to plug the modules in and
> go, is that right.? If more complicated, I will have to look for a
> professional as I don’t know much about electronics.! Hope I can fix it
> myself.
>
>
> 73,
> JosepEA6BFBUG #256  -  CWops #3072  -  FOC #2182 (ex 1724)
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Re: [Elecraft] KPA500 Voltage range?

[Lyn Norstad]

Yup.  That's exactly what's happening here - except the numbers are a notch
or two lower.

 

73

Lyn, W0LEN

 

 

From: Andy Durbin [mailto:a.dur...@msn.com] 
Sent: Wednesday, July 06, 2022 2:58 PM
To: elecraft@mailman.qth.net; l...@lnainc.com
Subject: Re: [Elecraft] KPA500 Voltage range?

 

"I though Elecraft wanted HV to be kept at or above 60 to avoid unacceptable
IMD.  No sure where I found that but don't think I imagined it. "

 

The problem with making measurements is that one may not like the results.
It's a nice warm afternoon here in Glendale AZ and I expect every air
conditioner in the street is running.  Line voltage is down to 116.4 and
loaded HV is well below 60 now.

 

 1:13:59.663  KPA Mon frozen 

  TX freq = 50314500 Hz

  Drv pwr = 027 W

  Pwr meter = 12 dots

  KAT SWR =  1.18

  KPA SWR = 01.2

  PA voltage = 56.8 V

  PA current = 13.7 A

  PA input = 778 W

  RF out = 495 W

  PA diss = 283 W

  PA effic = 63%

 

Andy, k3wyc

 

 

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Re: [Elecraft] KPA500 Voltage range?

[Andy Durbin]

"I though Elecraft wanted HV to be kept at or above 60 to avoid unacceptable 
IMD.  No sure where I found that but don't think I imagined it. "

The problem with making measurements is that one may not like the results.  
It's a nice warm afternoon here in Glendale AZ and I expect every air 
conditioner in the street is running.  Line voltage is down to 116.4 and loaded 
HV is well below 60 now.

 1:13:59.663  KPA Mon frozen
  TX freq = 50314500 Hz
  Drv pwr = 027 W
  Pwr meter = 12 dots
  KAT SWR =  1.18
  KPA SWR = 01.2
  PA voltage = 56.8 V
  PA current = 13.7 A
  PA input = 778 W
  RF out = 495 W
  PA diss = 283 W
  PA effic = 63%

Andy, k3wyc


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Re: [Elecraft] KPA500 Voltage range?

[Andy Durbin]

"Seems a little low, but it's happy."

I though Elecraft wanted HV to be kept at or above 60 to avoid unacceptable 
IMD.  No sure where I found that but don't think I imagined it.  Anyone have a 
reference?

Andy, k3wyc
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Re: [Elecraft] KPA500 Voltage range?

[Lyn Norstad]

Andy -

I'm also running 120. My HV idle runs about 68v, and under full load drops
to 50v @ 12a.

Seems a little low, but it's happy.

73
Lyn, W0LEN

-Original Message-
From: elecraft-boun...@mailman.qth.net
[mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Andy Durbin
Sent: Wednesday, July 06, 2022 12:00 PM
To: elecraft@mailman.qth.net
Subject: Re: [Elecraft] KPA500 Voltage range?

"I don't remember the AC, can check it later, but think its 231-232."

Your use of nominal 240 would explain why your HV sag is a lot less than
mine.  I have always run my KPA500 on 120.

Maybe someone who uses nominal 240 would provide their typical loaded and
unloaded HV values.

Andy, k3wyc


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Re: [Elecraft] KPA500 Voltage range?

[Andy Durbin]

"I don't remember the AC, can check it later, but think its 231-232."

Your use of nominal 240 would explain why your HV sag is a lot less than mine.  
I have always run my KPA500 on 120.

Maybe someone who uses nominal 240 would provide their typical loaded and 
unloaded HV values.

Andy, k3wyc


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Re: [Elecraft] KPA500 Voltage range?

[Gordon LaPoint]

Andy,
   Thanks, I'm looking for the VDC allowed voltage, unloaded and 
loaded.  I don't remember the AC, can check it later, but think its 231-232.

Gordon - N1MGO

On 7/6/2022 8:53 AM, Andy Durbin wrote:

"My kpa500 has the taps set to provide 71-72 VDC no load and drops to 60 at 500 
watts."

Do you know how your house line input voltage varies?   Mine can be as high as 
122 and as low as 118 and the local transformer is less than 50 ft from my 
house.

  I see unloaded KPA500 voltage over 80 with tap selected to keep loaded KPA500 
voltage at or above 60.   If your loaded voltage does not drop below 60 for all 
bands, all antenna loads, and all used output powers, I see no reason to change 
the tap.  Band, loading, and power output all have a very significant influence 
on efficiency, PA current, and voltage drop in the PA HV supply.

Spot check values:
Line voltage 122.0
Unloaded HV 81.4
TX 500 W, 6 m band, SWR 1.15, HV 60.3

Andy, k3wyc
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Re: [Elecraft] KPA500/KAT500 SOLD

[Bob McGraw]

KPA500 / KAT500  has been SOLD.

73

Bob, K4TAX

On 5/30/2022 8:52 PM, Bob McGraw wrote:
Making room for something else.   I have for sale my personal KPA500-F 
and KAT500-F.  Includes cables ready to connect to your K3 or K3S.   
Both items have the last release of firmware installed. Both items are 
in excellent condition and include cables and accessories.   Shown on 
my QRZ page.


KPA500-F s/n3519 purchased/received 4/25/2018.  Has original Elecraft 
box and packing.  Includes 240V power cable.


KAT500-F s/n 1807 purchased/received 10/23/2018.

Both have been on my desk in a non-smoking residential environment.  
Pictures are available on request.


Both items shipped to lower 48. $2600.00   Cash or cashier check.

931 256 0340

RMcGraw @ Benlomand dot Net


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Re: [Elecraft] KPA500 Mosfet SD2933 vs VRF2933

[Michael Carter]

Hi Ziv,

The SD2933 is an older part - Mouser lists it as 'obsolete'
and otherwise unavailable.  A review of the datasheets
for the two devices (VRF2933, SD2933) reveals that the
VRF2933 has a higher drain-source breakdown voltage
than the SD2933, and it is tolerant of SWR values up
to 70:1.  The SD2933 tolerates at least SWR of 3:1, possibly
greater, but that is the only spec in its datasheet.  The
VRF2933 has a somewhat lower gate capacitance than the
SD2933.  In other respects, the two MOSFETs are very similar.

I suspect the SD2933 will work in place of the VRF2933, but
you may need to watch the SWR on your antennas a bit more
carefully to avoid exceeding the maximum drain-source
breakdown voltage.  You will also need to carefully check
and adjust the gate bias voltage pots to ensure the proper
quiescent drain currents in each MOSFET.

73,
Mike, K8CN
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Re: [Elecraft] KPA500 Issue

[David Woolley]

Key clicks don't require non-linearity.  They are the result of 
modulating with a signal that has an infinite bandwidth, because of the 
sharp transitions at leading and trailing edges.  That results in 
infinite side bands.  (Actually any signal that communicates information 
in finite time will have infinite side bands, but by correct shaping you 
can make them very small.)


--
David Woolley
Owner K2 06123.


On 01/04/2022 23:06, Jim Brown wrote:

On 4/1/2022 2:35 PM, kevin wrote:

It is more accurately referenced as Discontinuous Wave.


Actually, it is 100% amplitude modulation of a carrier by a rectangular 
wave train. That modulation excites non-linearity in the transmitter 
signal chain and produce intermodulation distortion that is heard as 
clicks.



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Re: [Elecraft] KPA500 Issue

[James Bennett via Elecraft]

No - it does not spontaneously go into transmit more. The problem is that on 
the non-Elecraft radio, placing the KPA into transmit mode (with a button push 
on the KPA) drops the non-Elecraft radio’s receive signal tremendously. See 
Jack’s explanation in an earlier post on what the K3 is doing to the “system” 
when it is powered off.

Jim / K7TXA

> On Apr 1, 2022, at 6:44 PM, Andy Durbin  wrote:
> 
> "Just gave it a try. No joy, same result - lowered rx signal strength on the 
> IC-705.  Jack indicated that the K3 sets the Vcc rail to zero volts on power 
> off, and that is causing the amp to go into Operate mode. "
> 
> Maybe I lost the plot but wasn't the problem that the KPA500 was being keyed, 
> not that it spontaneously went to operate mode.  KPA500 won't be keyed unless 
> one of the two keying inputs is pulled low.
> 
> Take control of KPA keying source and doesn't the problem go away?
> 
> Andy, k3wyc
> 
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Re: [Elecraft] KPA500 Issue

[Jack Brindle via Elecraft]

I don’t think your point #1 is valid. The K3 will cause the KPA to change bands 
when it does a band change and sends out changed bits on the BAND signals. If 
you don’t change bands on the K3, then the KPA won’t have a reason to change. 
The problem with this, when RADIO = K3, is that tapping a band button on the 
KPA _will_ send an Auxbus command to the K3 indicating that a band button has 
been pressed. The key here is then to set the RADIO setting to something else. 
If you do not use the KPA to select a band on the K3, then try setting RADIO to 
BCD. Then, when the K3 changes bands, it will tell the KPA about the new band 
by changing the BAND signals, but the KPA will not send anything on the AUXBUS 
that causes the K3 to perform a band change.

The KPA500 is very versatile. If you make the right selection of its settings, 
it will do what you want. But it cannot overcome that PTT signal being held low 
by the K3. Use the KPA manual as a guide to tell you what you need to set and 
try it. And, for more information on this specific subject, get Fred Cady’s 
book on the KPA500. It has a lot of good info.

I still think that the use of the key block adapter along with a switch to 
select which PTT signal goes to the KPA500 & KAT500 would be your best bet. 
Also, buying a house without those restrictions… ;-)

For the those lurking, Jim and I have been friends for a long time, both 
members of the Northern California Contest Club. We escaped CA about the same 
time, commiserating on how expensive it was to move. At least I don’t have any 
restrictions now. It helps to be married to a ham who understands these things… 
;-)

Keep at it, Jim. I am sure we can devise a good solution for using both rigs.

73,
Jack, W6FB
PS. Watch for us in the La QSO Party on Saturday. It should be fun!


> On Apr 1, 2022, at 6:47 PM, James Bennett via Elecraft 
>  wrote:
> 
> Chuck,
> 
> Just gave it a try. No joy, same result - lowered rx signal strength on the 
> IC-705.  Jack indicated that the K3 sets the Vcc rail to zero volts on power 
> off, and that is causing the amp to go into Operate mode. 
> 
> I see the following options -
> 
> 1. Always put the K3 on the same band as the IC-705 if I want to run QRO with 
> the 705.
> 
> 2. Never use the 705 in QRO mode.
> 
> 3. Disconnect the K3 from the system, sell it, wait for the K4D to be 
> delivered, and use the 705 all by itself with the amp and tuner in the mean 
> time. 
> 
> Option #1 works but is a minor PITA. Option #2 - maybe. Option #3 - probably 
> the choice to make, as the K3/P3 was going to be sold anyway, in anticipation 
> of the K4D arrival. Just hoping I’ll live long enough to see the new radio 
> delivered.
> 
> Oh well, nothing in life is simple. At least I’ve got options and am able to 
> get on the air. :-)
> 
> 
> 
> 
>> On Apr 1, 2022, at 3:51 PM, Chuck Chandler  wrote:
>> 
>> Hhhmmm... I'm coming late to this thread, as I wasn't paying attention
>> before.
>> 
>> Please forgive me if I have missed something but -
>> 
>> I have, in the past, used both a K3S AND an old Yaesu FT-101ZD with my
>> KPA/KAT 500 power combo.  I *THINK* that is similar to what Jim is trying
>> to do.
>> 
>> Here is what I found, if it helps.
>> 
>> When the K3S is on, it communicates with the KAT/KPA.  However, when it is
>> turned off, it leaves the KPA/KAT in a state where they are not prepared to
>> accept input.  I forget the specifics, because I have since provided the
>> 101ZD with it's own amp.
>> 
>> Try this - Turn off the K3S.  Turn off the KPA.
>> 
>> Turn the KPA back on, with the other radio connected to the RF input and at
>> least an RCA keyline connected for the PTT.  See if it works.
>> 
>> IIRC, this was what I had to do.
>> 
>> If anyone needs the specifics as to WHY it works that way, I can try to dig
>> out the old emails with Elecraft.  And, it's been a while so I may be
>> mis-remembering the details.  But, I know it worked.
>> 
>> I hope this helps...
>> 
>> 73 de Chuck, WS1L
>> 
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Re: [Elecraft] KPA500 Issue

[Andy Durbin]

"Just gave it a try. No joy, same result - lowered rx signal strength on the 
IC-705.  Jack indicated that the K3 sets the Vcc rail to zero volts on power 
off, and that is causing the amp to go into Operate mode. "

Maybe I lost the plot but wasn't the problem that the KPA500 was being keyed, 
not that it spontaneously went to operate mode.  KPA500 won't be keyed unless 
one of the two keying inputs is pulled low.

Take control of KPA keying source and doesn't the problem go away?

Andy, k3wyc

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Re: [Elecraft] KPA500 Issue

[James Bennett via Elecraft]

Chuck,

Just gave it a try. No joy, same result - lowered rx signal strength on the 
IC-705.  Jack indicated that the K3 sets the Vcc rail to zero volts on power 
off, and that is causing the amp to go into Operate mode. 

I see the following options -

1. Always put the K3 on the same band as the IC-705 if I want to run QRO with 
the 705.

2. Never use the 705 in QRO mode.

3. Disconnect the K3 from the system, sell it, wait for the K4D to be 
delivered, and use the 705 all by itself with the amp and tuner in the mean 
time. 

Option #1 works but is a minor PITA. Option #2 - maybe. Option #3 - probably 
the choice to make, as the K3/P3 was going to be sold anyway, in anticipation 
of the K4D arrival. Just hoping I’ll live long enough to see the new radio 
delivered.

Oh well, nothing in life is simple. At least I’ve got options and am able to 
get on the air. :-)




> On Apr 1, 2022, at 3:51 PM, Chuck Chandler  wrote:
> 
> Hhhmmm... I'm coming late to this thread, as I wasn't paying attention
> before.
> 
> Please forgive me if I have missed something but -
> 
> I have, in the past, used both a K3S AND an old Yaesu FT-101ZD with my
> KPA/KAT 500 power combo.  I *THINK* that is similar to what Jim is trying
> to do.
> 
> Here is what I found, if it helps.
> 
> When the K3S is on, it communicates with the KAT/KPA.  However, when it is
> turned off, it leaves the KPA/KAT in a state where they are not prepared to
> accept input.  I forget the specifics, because I have since provided the
> 101ZD with it's own amp.
> 
> Try this - Turn off the K3S.  Turn off the KPA.
> 
> Turn the KPA back on, with the other radio connected to the RF input and at
> least an RCA keyline connected for the PTT.  See if it works.
> 
> IIRC, this was what I had to do.
> 
> If anyone needs the specifics as to WHY it works that way, I can try to dig
> out the old emails with Elecraft.  And, it's been a while so I may be
> mis-remembering the details.  But, I know it worked.
> 
> I hope this helps...
> 
> 73 de Chuck, WS1L
> 
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Re: [Elecraft] KPA500 Issue

[Fred Jensen]

Or perhaps OOKPWM?  That was the only available modulating technique for 
spark transmitters.  For all it's apparent simplicity, it is still 
possible to create a rotten signal, and it is notoriously difficult to 
decode ... unless you're a human being.


My modest home station is comprised of only a K3, P3, RemoteRig 
RRC-1258, Winkey, 3 paddles, and one hand key, and the "behind the desk" 
part certainly does not look like "wireless." 


73,

Fred ["Skip"] K6DGW
Sparks NV DM09dn
Washoe County

Jim Brown wrote on 4/1/2022 3:06 PM:

On 4/1/2022 2:35 PM, kevin wrote:

It is more accurately referenced as Discontinuous Wave.


Actually, it is 100% amplitude modulation of a carrier by a 
rectangular wave train. That modulation excites non-linearity in the 
transmitter signal chain and produce intermodulation distortion that 
is heard as clicks.


73, Jim K9YC




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Re: [Elecraft] KPA500 Issue

[Jim Brown]

On 4/1/2022 2:35 PM, kevin wrote:

It is more accurately referenced as Discontinuous Wave.


Actually, it is 100% amplitude modulation of a carrier by a rectangular 
wave train. That modulation excites non-linearity in the transmitter 
signal chain and produce intermodulation distortion that is heard as clicks.


73, Jim K9YC
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Re: [Elecraft] KPA500 Issue

[Chuck Chandler]

Hhhmmm... I'm coming late to this thread, as I wasn't paying attention
before.

Please forgive me if I have missed something but -

I have, in the past, used both a K3S AND an old Yaesu FT-101ZD with my
KPA/KAT 500 power combo.  I *THINK* that is similar to what Jim is trying
to do.

Here is what I found, if it helps.

When the K3S is on, it communicates with the KAT/KPA.  However, when it is
turned off, it leaves the KPA/KAT in a state where they are not prepared to
accept input.  I forget the specifics, because I have since provided the
101ZD with it's own amp.

Try this - Turn off the K3S.  Turn off the KPA.

Turn the KPA back on, with the other radio connected to the RF input and at
least an RCA keyline connected for the PTT.  See if it works.

IIRC, this was what I had to do.

If anyone needs the specifics as to WHY it works that way, I can try to dig
out the old emails with Elecraft.  And, it's been a while so I may be
mis-remembering the details.  But, I know it worked.

I hope this helps...

73 de Chuck, WS1L

chandler...@gmail.com


On Fri, Apr 1, 2022 at 11:01 AM James Bennett via Elecraft <
elecraft@mailman.qth.net> wrote:

> Well, it looks like there is no simple solution to this dilemma. I was
> hoping to (easily) be able to use the amp with either rig while both were
> here in the shack. Pulling the audio cable when I want to use the IC-705
> with the amp isn’t practical due to the location of the radio. I changed
> the “Radio” setting from K3 to Analog and Serial, but with the cables
> attached, the result is the same - as soon as the amp is put in OPER mode
> it goes into transmit state (* showing on the LCD).
>
> So, the only option for the time being is to always have the K3 powered up
> and on the band that I want to operate the IC-705 on. Just need to keep
> their frequencies separated as much as I can. Unless Jack comes up with an
> alternate…! :-) :-)
>
> Jim / K7TXA
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Re: [Elecraft] KPA500 Issue

[kevin]

For the same reason we call using Morse Code CW.

It is more accurately referenced as Discontinuous Wave.

   73,  Kevin.  KD5ONS


On 4/1/22 13:23, Fred Jensen wrote:

Why do we call this "wireless?"

73,

Fred ["Skip"] K6DGW
Sparks NV DM09dn
Washoe County

Jack Brindle via Elecraft wrote on 3/31/2022 9:47 PM:
OK, now this is starting to make sense. Jim’s K3 has a KIO3, not the 
newer KIO3B. On the older board, the BAND and PTT lines have pullup 
resistors to the Vcc rail.
When the K3 is powered off, that Vcc rail is at 0 volts, which means 
the pull-ups are now pulldowns. Thus the K3 is inadvertently keying 
the KPA500. If the KPA
detects that the KEY input is low when the user tries to put it into 
OPER mode, the amplifier will reject the request and stay in STBY. 
Thus the condition that

Jim is seeing.

Try disconnecting the AUXIO cable from the KPA500 and see if it now 
operates properly. You may actually need to connect the KAT500 to the 
KPA using both the AuxIO

and phono cables (for PTT) depending on which radio is in use.

The main issue is how to disconnect the PTT signal from the K3 to the 
KPA when using the Icom. Otherwise you may be able to leave the AuxIO 
cable connected.
I know that Fred Cady discussed sharing a KPA between two radios in 
his book, but has anyone solved this situation - one radio is a K3, 
the other something else?


73,
Jack, W6FB






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Re: [Elecraft] KPA500 Issue

[Fred Jensen]

Why do we call this "wireless?"

73,

Fred ["Skip"] K6DGW
Sparks NV DM09dn
Washoe County

Jack Brindle via Elecraft wrote on 3/31/2022 9:47 PM:

OK, now this is starting to make sense. Jim’s K3 has a KIO3, not the newer 
KIO3B. On the older board, the BAND and PTT lines have pullup resistors to the 
Vcc rail.
When the K3 is powered off, that Vcc rail is at 0 volts, which means the 
pull-ups are now pulldowns. Thus the K3 is inadvertently keying the KPA500. If 
the KPA
detects that the KEY input is low when the user tries to put it into OPER mode, 
the amplifier will reject the request and stay in STBY. Thus the condition that
Jim is seeing.

Try disconnecting the AUXIO cable from the KPA500 and see if it now operates 
properly. You may actually need to connect the KAT500 to the KPA using both the 
AuxIO
and phono cables (for PTT) depending on which radio is in use.

The main issue is how to disconnect the PTT signal from the K3 to the KPA when 
using the Icom. Otherwise you may be able to leave the AuxIO cable connected.
I know that Fred Cady discussed sharing a KPA between two radios in his book, 
but has anyone solved this situation - one radio is a K3, the other something 
else?

73,
Jack, W6FB





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Re: [Elecraft] KPA500 Issue

[ws6x.ars]

Jim,
You are correct! It is clearly not the same problem. I was trying to correct my 
"bad memory" offering from last evening.
Thanks, Jim - WS6X 

-Original Message-
From: elecraft-boun...@mailman.qth.net On Behalf Of James Bennett via Elecraft
Sent: Friday, April 01, 2022 3:36 PM
To: Elecraft Reflector Reflector 
Subject: Re: [Elecraft] KPA500 Issue

Jim,

I don’t think this is the same problem as you had. The receive signal on my K3 
does NOT drop off when placing the amp in OPER. With my antenna switched over 
to the IC-705 (not the K3), the received signal does drop off when the amp is 
placed into OPER mode. Thus, I’m pretty certain that R7 and the PIN diodes are 
OK - the K3 is not affected. 

Jim / K7TXA 

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Re: [Elecraft] KPA500 Issue

[James Bennett via Elecraft]

Jim,

I don’t think this is the same problem as you had. The receive signal on my K3 
does NOT drop off when placing the amp in OPER. With my antenna switched over 
to the IC-705 (not the K3), the received signal does drop off when the amp is 
placed into OPER mode. Thus, I’m pretty certain that R7 and the PIN diodes are 
OK - the K3 is not affected. 

Jim / K7TXA
> 
> Jim, Andy et al,
> 
> I weighed in on this thread last evening from memory in response to Andy's
> comment, above. By age 77, I should have learned not to rely on memory. As
> it turns out, my memory was faulty.
> 
> So, even though it appears many have pointed Jim to a useful, unrelated
> solution, I will now provide the correct information about the issue and fix
> with my KPA500 almost one year ago.
> 
> At first glance, my symptoms were nearly identical to what Jim is reporting:
> With ALL control cables between the K3s and the KPA500 completely
> disconnected (only the input and output coax cables connected to the amp),
> every time the amp is manually switched from "STBY" to "OPER" the receive
> signal on the K3s dropped about 20 dB.
> 
> As many suggested, the problem was in the T/R circuit. In my case the
> culprit was R7. This 51 Ohm resistor was toast -- completely open. My fix
> was to parallel a pair of 1/4 Watt, 100 Ohm resistors across the R7 pads.
> Problem solved. The KPA500 has been on good behavior since.
> 
> Hopefully, this information might be useful to someone in the future.
> 
> Jim - WS6X 
> 
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Re: [Elecraft] KPA500 Issue

[ws6x.ars]

"However, what I'm seeing is that when the amp is in OPER mode, my receive
signal strength drops way, way off to the point I have to go full AF volume
to hear signals. If I put the amp in STBY, signal levels go back to normal."

These exact symptoms have been associated in past reports with a failure of
the TR switch PIN diodes.  Jack's idea of incorrect band can be easily
confirmed, or eliminated, by looking at the KPA500 band display.

Andy, k3wyc



Jim, Andy et al,

I weighed in on this thread last evening from memory in response to Andy's
comment, above. By age 77, I should have learned not to rely on memory. As
it turns out, my memory was faulty.

So, even though it appears many have pointed Jim to a useful, unrelated
solution, I will now provide the correct information about the issue and fix
with my KPA500 almost one year ago.

At first glance, my symptoms were nearly identical to what Jim is reporting:
With ALL control cables between the K3s and the KPA500 completely
disconnected (only the input and output coax cables connected to the amp),
every time the amp is manually switched from "STBY" to "OPER" the receive
signal on the K3s dropped about 20 dB.

As many suggested, the problem was in the T/R circuit. In my case the
culprit was R7. This 51 Ohm resistor was toast -- completely open. My fix
was to parallel a pair of 1/4 Watt, 100 Ohm resistors across the R7 pads.
Problem solved. The KPA500 has been on good behavior since.

Hopefully, this information might be useful to someone in the future.

Jim - WS6X 

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Re: [Elecraft] KPA500 Issue

[Ken K6MR]

"However, if the rigs are on different bands, you do need to rely on frequency 
sensing by the amp."

You don't have to do this, but it does take a bit of extra hardware/software to 
interface two K3s to a KPA1500.  In addition to the necessary relays to switch 
the RF path you can use an Arduino to manage the band data as well as the Aux 
Bus messages.  I also use a MicroHam MK2R+ to point the amp at the correct 
radio.  It is seamless.  I have the amp in a closet and never touch it, 
monitored only by the remote software.  I can switch instantly between radios 
in a SO2R setup and interleave QSOs.

Ken K6MR



From: elecraft-boun...@mailman.qth.net  on 
behalf of Frank Scolaro 
Sent: Friday, April 1, 2022 8:46 AM
To: James Bennett ; Elecraft Reflector Reflector 

Subject: Re: [Elecraft] KPA500 Issue

Jim,.

I use the "1A2R" (one amp tw0 radios) from 4O4A.  I have two rigs share my 
KPA1500.  However, if the rigs are on different bands, you do need to rely on 
frequency sensing by the amp.  Not sure if the KPA500 does that.

GL
Frank, W2YK

-Original Message-
From: James Bennett
Sent: Apr 1, 2022 11:02 AM
To: Elecraft Reflector Reflector
Subject: Re: [Elecraft] KPA500 Issue

Well, it looks like there is no simple solution to this dilemma. I was hoping 
to (easily) be able to use the amp with either rig while both were here in the 
shack. Pulling the audio cable when I want to use the IC-705 with the amp isn’t 
practical due to the location of the radio. I changed the “Radio” setting from 
K3 to Analog and Serial, but with the cables attached, the result is the same - 
as soon as the amp is put in OPER mode it goes into transmit state (* showing 
on the LCD).

So, the only option for the time being is to always have the K3 powered up and 
on the band that I want to operate the IC-705 on. Just need to keep their 
frequencies separated as much as I can. Unless Jack comes up with an 
alternate…! :-) :-)

Jim / K7TXA
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Re: [Elecraft] KPA500 Issue

[RALPH TURK]

In the attached email Frank W2yk wrote the 1A2R from 404A.  I only find a 403.
Please advise 
Ralph, w7HSG/AFA9RT
> On 04/01/2022 9:48 AM Rick Bates, NK7I  wrote:
> 
>  
> It does.  But you HAVE to remember to send a dit on each band change so 
> the amp knows where you are.
> 
> 73,
> Rick NK7I
> 
> 
> On 4/1/2022 8:46 AM, Frank Scolaro wrote:
> > Jim,.
> >   
> > I use the "1A2R" (one amp tw0 radios) from 4O4A.  I have two rigs share my 
> > KPA1500.  However, if the rigs are on different bands, you do need to rely 
> > on frequency sensing by the amp.  Not sure if the KPA500 does that.
> >   
> > GL
> > Frank, W2YK
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Re: [Elecraft] KPA500 Issue

[Andy Durbin]

"Pulling the audio cable when I want to use the IC-705 with the amp isn’t 
practical due to the location of the radio."

The high density 15 pin connectors used on the Aux cable is readily available 
and inexpensive. Why not make an adapter that allows the PTT line (pin 10)  to 
be switched between K3 and Icom?

AUX pin 10 (Ken in) and RCA Key jack are diode OR'd to drive the same KA500 
internal Keying signal.

Andy, k3wyc

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