"my KPA500 seems to have an excessive amount of hum/buzz when transmitting.
What should I look for?"
Ask Elecraft support to send you the paper "KPA500 Application Note - Hum
Mitigation". Also ask about the mod kit that includes a longer transformer
hold down bolt an extras rubber disks.
Thanks. I’ll try that.
73, John N1JM
> On Jun 2, 2019, at 6:12 PM, hawley, charles j jr
> wrote:
>
> Readjust the toroid hold down? Maybe rotate it a bit. Just make a change of
> some kind...
>
> Chuck Jack
> KE9UW
>
> Sent from my iPhone, cjack
>
>> On Jun 2, 2019, at 5:59 PM, John
Readjust the toroid hold down? Maybe rotate it a bit. Just make a change of
some kind...
Chuck Jack
KE9UW
Sent from my iPhone, cjack
> On Jun 2, 2019, at 5:59 PM, John Merrill wrote:
>
> Probably has been discusses before but my KPA500 seems to have an excessive
> amount of hum/buzz when
Probably has been discusses before but my KPA500 seems to have an excessive
amount of hum/buzz when transmitting. What should I look for?
73, John N1JM
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Prob. The front switch is a “soft switch”. Wakes up the amp from a nap.
Sent from my iPhone
...nr4c. bill
> On Jan 4, 2019, at 12:57 AM, John_N1JM wrote:
>
> I don't use my KPA500 a lot, but I just noticed with only the back switch on
> I can hear a hum coming from the amp. It disappears of
On 1/4/2019 10:52 AM, Bob McGraw K4TAX wrote:
Mark et al:
Your description raises a bit of concern. Not with the amplifier but
with your power distribution in your home / QTH.
Yes. This is the symptom of one or more mis-wired outlets, or of an
extra bond between neutral and ground
Mark et al:
Your description raises a bit of concern. Not with the amplifier but
with your power distribution in your home / QTH.
First I'll presume you are running the amp on 120V and not 240V. Thus
being so, as the coffee maker comes on or curling iron comes on the
Neutral current
John,
When my KPA500 hums, I assume it is a power quality problem.
It only hums when a curling iron or coffee maker, both of which are on
different circuits, are in operation.
--mark/ae0mm
‐‐‐ Original Message ‐‐‐
On Friday, January 4, 2019 8:14 AM, John_N1JM wrote:
> Thanks Bob.
Thanks Bob. Yes great amp.
73, John N1JM
Bob McGraw - K4TAX wrote
> Yes it is normal to hear a slight hum when the Mains switch is on. Also
> the left side may be slightly warm. When the Mains switch is on, the
> low voltage power supply is on. This supply is for the logic and
>
Yes it is normal to hear a slight hum when the Mains switch is on. Also
the left side may be slightly warm. When the Mains switch is on, the
low voltage power supply is on. This supply is for the logic and
processing.
See the IMPORTANT section on page 14 of the manual for further
I don't use my KPA500 a lot, but I just noticed with only the back switch on
I can hear a hum coming from the amp. It disappears of course when I turn
the switch off. Is this normal?
73, John N1JM
--
Sent from: http://elecraft.365791.n2.nabble.com/
Hum level depends on PA current draw from the torroidal transformer. What is
your PA voltage key down? What is the complex impedance of the antenna system
as measured at the amplifier?
I reduced my KPA500 hum level from intolerable to acceptable by adjusting the
transformer voltage tap and
I suspect that may be the case, Bob. I will wait until I hear from tech support
before I pop open then amplifier for a look-see. It is factory built.
Regarding power output, I was incorrect. On 80 and 40 meters I am seeing
similar outputs as you. I am on a 240 source, HV is 74 volts.
John
Zero hum from mine. From other comments, be sure the power transformer
is correctly installed and secured. It may have moved during
transportation if you purchased a factory built unit.
As to 20 watts drive and 350 watts out, what bands? With 20 watts
drive from my K3S I see 450 to 550
I'm certainly having my troubles with this new KPA500. The level of hum is
unacceptable.
The manual says it is normal to hear hum. With 20 w drive I'm getting 350 watts
out but the hum is horrendous when I send CW. SSB not so bad. Is this level of
hum normal during keydown? It's room
I run my amp on 240 VAC with the yellow tap as supplied from the
factory. No hum or buzz when operating 550 watts output. Drive on 6M
is 30 watts. SWR is 1.2:1 or better. Other bands the same. The
KAT500 memory is "trained" every 50 kHz on all band below 10M. In
fact with my ear
When I first started using my KPA500 I found the hum/buzz during high power CW
operation to be intolerable. Elecraft support sent me a paper on hum
reduction, a longer transformer bolt, and additional rubber washers. I did not
use any of this new hardware but now have acceptable hum/buzz
Hi Eric
It isn't a continuous hum, nor does it sound like a small transformer. It
comes on for perhaps 15 seconds, sometimes more, then goes away. Nothing
shows on the front panel when this happens as it is off but back panel
switch is on. It sounds more like a big transformer hum.
I've got a
I leave my KPA500 back panel switch in the ON position most of the time and
use the front panel switch to bring it to life.
However in even when in the Front panel off/Back panel on state the
KPA500 will occasionally hum for a few seconds.
Is this normal? Any suggested causes to worry about?
Jim
The KPA500 turns on the fan momentarily when you use the front panel on/off
switch. I believe this is to bleed off voltage in the internal power supply. It
is a design consideration not a problem
Harlan
NC3C
Sent from my Verizon Wireless 4G LTE DROID
Jim Miller j...@jtmiller.com wrote:
Jim,
My first KPA500 did that occasionally, so I don't think it's an issue.
I'd guess it has to do with line voltage variances.
73,
Scott, N9AA
On 6/11/13 10:51 AM, Jim Miller wrote:
I leave my KPA500 back panel switch in the ON position most of the time and
use the front panel switch to
Jim;
Make sure the transformer is bolted down appropriately. If it works loose then
it will cause the hum.
Jack Brindle, W6FB
On Jun 11, 2013, at 7:51 AM, Jim Miller j...@jtmiller.com wrote:
I leave my KPA500 back panel switch in the ON position most of the time and
use the front panel
It's not fan noise. It's definitely 60hz hum likely due to transformer for
some reason. This was a factory assembled unit. I'll take the lid off and
check it out the bolting. I'm currently running on a shared household
circuit with who-knows-what connected elsewhere. The shack will get a
dedicated
I have a kit-built KPA500 that has the same issue.
It's well grounded and all the bolts are tight.
The humm is barely noticeable when off but definitely there.
73
Stan AE7UT
--
View this message in context:
http://elecraft.365791.n2.nabble.com/KPA500-Hum-when-off-tp7575069p7575086.html
Sent
My kit built hums but only periodically - more like a cycle and certainly not a
continuous hum. When it happens I can fear it if the room is quiet. Capacitor
recharging?
On Jun 11, 2013, at 12:13 PM, Stan AE7UT ae7...@gmail.com wrote:
I have a kit-built KPA500 that has the same issue.
It's
Jim,
As someone else mentioned, it is most likely due to line voltage variance.
Even though they are on different circuits, whenever my wife uses the blow
dryer, the KPA500 starts humming along. I guess that doesn't speak well
for connections somewhere between the electric company and my ac
This is normal and is due to the small low voltage transformer and
rectifiers that provide power to the front panel microprocessor. turning
off the rear switch will turn everything off, including this transformer.
Eric
elecraft.com
On 6/11/2013 10:13 AM, Stan AE7UT wrote:
I have a kit-built
I had this happen and discovered that the laser printer I had was plugged into
the same ac circuit and was causing voltage drop periodically. Moving the
printer to another wall outlet fixed the problem.
Matt NQ6N
On Jun 11, 2013, at 5:03 PM, Eric Swartz - WA6HHQ, Elecraft
e...@elecraft.com
A low level of AC hum is normal with products like the KPA500 that use
a high-power linear supply.
Nearly all reports of KPA500 hum have come from kit builders. So we
did some reverse engineering of our kit building process to see how to
make the normal hum worse. In the process we found
︰ Elecraft Reflector elecraft@mailman.qth.net
傳送日期︰ 2011年09月29日 (週四) 7:40 AM
主題︰ [Elecraft] KPA500 hum
A low level of AC hum is normal with products like the KPA500 that use
a high-power linear supply.
Nearly all reports of KPA500 hum have come from kit builders. So we
did some reverse
Wayne,
I have not purchased my KPA500 yet but I do want to understand anything you
say. Now, I don't understand item (1) below about using the yellow (lowest
voltage) tap.
I think my problem is possibly perspective but in reading the manual, the yellow
tap is associated with the highest primary
Hi Phil,
Wayne was referring to the highest supply voltage internal to the amplifier
which increases in steps when moving from the yellow to the red, to the
green tap. It is a bit confusing because the highest voltage tap would be
used with the lowest AC mains voltage to maintain the operating
從︰ Phil Hystad phys...@mac.com
收件人︰ Wayne Burdick n...@elecraft.com
副本(CC)︰ Elecraft Reflector elecraft@mailman.qth.net
傳送日期︰ 2011年09月29日 (週四) 11:56 AM
主題︰ Re: [Elecraft] KPA500 hum
Wayne,
I have not purchased my KPA500 yet but I do want to understand anything you
Ron D'Eau Claire wrote:
Mike, I certainly concur with Eric's observation. What I thought was
very unusual was that you said that the hum would come and go, which I
presume happens when you aren't doing anything at the amp.
Hum that comes and goes for no apparent reason might be caused by some
Hope there comes a hardware mod to obtain minimum hum.
73
Arie PA3A
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...@xs4all.nl
收件人︰ elecraft@mailman.qth.net
傳送日期︰ 2011年09月27日 (週二) 9:23 PM
主題︰ Re: [Elecraft] KPA500 Hum
Hope there comes a hardware mod to obtain minimum hum.
73
Arie PA3A
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Referring to kit assembly instructions, Rev B, June 22, 2011:
The following is on page 33. When placing the transformer on the chassis
you are told to press it toward the Z-Bracket so it does not hit the rubber
bumpers installed earlier. Then
above figure 49 on the same page it says the
I did as you Roy but if I press my ear to the top of the KPA500 case I can
hear a faint hum. It is the same with my 12v linear power supply underneath
the bench. I do not believe it is a fault but fairly normal for linear power
supplies. Occasionally both the KPA500 and the power supply under
Another issue is what the amp is resting upon.
Back when I first got my Alpha 76PA, I had a noticeable hum when
transmitting. When I wised up a little, I tried it from different places
and noted that the volume had a very large variation depending on where
placed on the upper shelf or simply
Yes, the resonating board may explain the difference between various
perceptions of KPA500 owners about the hum level. To check for that, it
is a simple matter of lifting the KPA500 up with your hands - if the hum
level diminishes, then the surface it is sitting on is acting as an
acoustical
Dave,
Yes, you are correct, the foam may take some time to recover, but if
loosening the bolt makes a change, then that is the problem.
I am doing well, and in fact this weekend, my antenna farm will get
higher. I have a crew coming over to put the VHF/UHF antenna on the 48
foot tower - that
My KPA500 now seems to have the hummms. It comes and goes whether the
unit is on or off. It does go away when you turn off the rear switch.
I noticed someone changed the tap and that appeared to fix the hum.
I am running the amp on 110V. My actual wall voltage is 119V.
I did not notice this
What you are describing is very unusual, Mike.
Typically, one will hear some hum from the transformer with the key down
(full 500 watt carrier). It is most pronounced when using the green
transformer tap (lowest line voltage input). Normally there is no hum with
the KPA500 off, or when running
Hi Mike,
This doesn't sound unusual.
There is also a normal amount of 'resting' idle low level transformer
hum, which varies with line voltage and frequency. Also, when the rear
switch is on, the transformer primary is active even when the front
switch is off ( but the output windings are
Ok. I just never heard it before. I did recall others mentioning
this. It is not loud. The amp works great.
J6/W0MU November 21 - December 1 2011 CQ WW DX CW
W0MU-1 CC Cluster w0mu.net
On 9/26/2011 1:07 PM, Eric Swartz - WA6HHQ, Elecraft wrote:
Hi Mike,
This doesn't sound unusual.
Mike, I certainly concur with Eric's observation. What I thought was very
unusual was that you said that the hum would come and go, which I presume
happens when you aren't doing anything at the amp.
Did you build your amp yourself from the kit? Since you said the hum seems
to have increased
Twice mine has hummed loudly enough (always when off from the front, on from
the rear) that I looked for the noise, and unplugged it. I guess perhaps
it's related to line voltage, which changes. I will monitor line voltage
with my KILL-A-WATT meter and see if I can correlate it.
Leigh/WA5ZNU
Hi
I see this has been mentioned before - but my KPA500 was pretty quiet when I
first got it (plugged in - but not 'ON')
Now - sometimes - it has a pretty loud hum while 'OFF' - I turned the power
switch at back on / off a couple of times - and it quieted down.. after a
couple of minutes it
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