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
>
> __
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Elecraft@mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to va...@portcredit.net
>
__
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Elecraft@mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to a...@sbcglobal.net 
  
__
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Elecraft@mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to arch...@mail-archive.com 

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
>
> __
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Elecraft@mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to va...@portcredit.net
>
__
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Elecraft@mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to arch...@mail-archive.com 

[Elecraft] KPA500 transformer removal

[n1ix]

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

__
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Elecraft@mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to arch...@mail-archive.com 

Re: [Elecraft] KPA500 Transformer

[Jack Brindle via Elecraft]

Gee Alan, we get told that all the time, specially by coworkers… 

As for the transformer, the tech support guys give good advice here. Place the 
rubber disks below the transformer in the appropriate places, and one above as 
the instructions indicate.
Essentially you want to get the transformer off the base chassis enough to keep 
it from vibrating against it. We all worry about tightening the nut down too 
much, which is why we added the torque wrench suggestion in the manual. But it 
does need to be rather tight to keep things from vibrating. Also, make sure all 
the screws in the chassis are tight. The hum can come from other parts as well. 
Making sure thins like the rectifier board are properly tight can help 
alleviate this situation also.

Someone asked about keeping the rear-panel power on. I have the first KPA500 
still in operation, and it has seen very little rear-panel off time during its 
life. In this situation, the power supply is on, and the microcontroller is on 
in sleep mode. This means the unit does draw current, but not very much. I have 
seen no effect from it on my power bill. During months when I participate in 
contests I can’t say that - running 500 or so watts for long periods each 
weekend does spin the power meter a bit.

Thanks for the compliment, we work very hard to create, build and support 
products that make you guys happy. I think it shows.

73!
Jack, W6FB
Elecraft Engineering


> On Oct 20, 2020, at 2:27 PM, Alan - G4GNX  wrote:
> 
> Guys. My comment was sarcastic and has a smiley on the end of it. Elecraft 
> know what they're doing and I would not expect anyone to tell them they got 
> it wrong!
> 
> 73,
> 
> Alan. G4GNX
> 
> 
> -- Original Message --
> From: "Nr4c" 
> To: "Alan - G4GNX" 
> Cc: "Elecraft Reflector" 
> Sent: 20/10/2020 19:42:31
> Subject: Re: [Elecraft] KPA500 Transformer
> 
>> No,  no. The torque wrench is used to insure the proper torque is applied.
>> 
>> A torque wrench is not a torque multiplier, it is a measurement instrument.
>> 
>> Sent from my iPhone
>> ...nr4c. bill
>> 
>> 
>>> On Oct 20, 2020, at 6:33 AM, Alan - G4GNX  wrote:
>>> 
>>> Then perhaps someone needs to educate Elecraft not to specify use of a 
>>> torque wrench, in their assembly instructions. ;-)
>>> 
>>> 73,
>>> 
>>> Alan. G4GNX
>>> 
>>> 
> 
> __
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Elecraft@mailman.qth.net
> 
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to jackbrin...@me.com

__
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Elecraft@mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to arch...@mail-archive.com 

Re: [Elecraft] KPA500 Transformer

[Alan - G4GNX]

Guys. My comment was sarcastic and has a smiley on the end of it. 
Elecraft know what they're doing and I would not expect anyone to tell 
them they got it wrong!


73,

Alan. G4GNX


-- Original Message --
From: "Nr4c" 
To: "Alan - G4GNX" 
Cc: "Elecraft Reflector" 
Sent: 20/10/2020 19:42:31
Subject: Re: [Elecraft] KPA500 Transformer


 No,  no. The torque wrench is used to insure the proper torque is applied.

A torque wrench is not a torque multiplier, it is a measurement instrument.

Sent from my iPhone
...nr4c. bill



 On Oct 20, 2020, at 6:33 AM, Alan - G4GNX  wrote:

 Then perhaps someone needs to educate Elecraft not to specify use of a torque 
wrench, in their assembly instructions. ;-)

 73,

 Alan. G4GNX




__
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Elecraft@mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to arch...@mail-archive.com 

Re: [Elecraft] KPA500 Transformer

[Josh Fiden]

Yes. 100% of the time I’ve specified using a calibrated torque wrench or driver 
in an assembly procedure is to prevent *too much* torque from being applied. 

73
Josh W6XU

Sent from my mobile device

> On Oct 20, 2020, at 11:43 AM, Nr4c  wrote:
> 
>  No,  no. The torque wrench is used to insure the proper torque is applied. 
> 
> A torque wrench is not a torque multiplier, it is a measurement instrument. 
> 

__
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Elecraft@mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to arch...@mail-archive.com 

Re: [Elecraft] KPA500 Transformer

[Harry Yingst via Elecraft]

 Here is a video that shows what the root issue may actually be.
https://youtu.be/80XN7OHoBSc




On Tuesday, October 20, 2020, 02:11:51 PM EDT, David Gilbert 
 wrote:  
 
 
Because everyone who now owns a KPA500 owned it years ago and was a list 
member back then??

Besides, I've been a member of this list since at least 2008 and I can 
recall many KPA500 owners still complaining about hum even after trying 
to follow all of the advice given here.  It's still a valid topic and 
not outside the list boundary rules.

And of course, every single post in this recent KPA500 hum thread has 
been clearly identified in the headline and could be easily ignored or 
deleted by anyone who was able to read it.  You could have done so 
yourself in far less time than it took you to write your post.

Dave  AB7E



On 10/19/2020 9:34 PM, Eric Norris wrote:
> The torque spec is called out in the manual.  Why not use a torque wrench?
> Can we please not resurrect the KPA500 hum thread already beat to death
> multiple times years ago?  Or does everyone need to chime in yet again?
>
> 55 inch-pounds.
>
> 73 Eric WD6DBM

__
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Elecraft@mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to hlyin...@yahoo.com   
__
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Elecraft@mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to arch...@mail-archive.com 

Re: [Elecraft] KPA500 Transformer

[Nr4c]

 No,  no. The torque wrench is used to insure the proper torque is applied. 

A torque wrench is not a torque multiplier, it is a measurement instrument. 

Sent from my iPhone
...nr4c. bill


> On Oct 20, 2020, at 6:33 AM, Alan - G4GNX  wrote:
> 
> Then perhaps someone needs to educate Elecraft not to specify use of a 
> torque wrench, in their assembly instructions. ;-)
> 
> 73,
> 
> Alan. G4GNX
> 
> 
> -- Original Message --
> From: "Bert" 
> To: elecraft@mailman.qth.net
> Sent: 20/10/2020 05:15:21
> Subject: Re: [Elecraft] KPA500 Transformer
> 
>> Toroidal transformers cause very little acoustic hum, unless the core
>> is not tightly wound or the copper wire windings are loose!
>> 
>> If you have to tighten the mounting bolt with a torque wrench
>> to get the transformer quiet, something is wrong!
>> 
>> Bert VE3NR
>> 
> 
> __
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Elecraft@mailman.qth.net
> 
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to n...@widomaker.com 
__
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Elecraft@mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to arch...@mail-archive.com 

Re: [Elecraft] KPA500 Transformer

[David Gilbert]

Because everyone who now owns a KPA500 owned it years ago and was a list 
member back then??


Besides, I've been a member of this list since at least 2008 and I can 
recall many KPA500 owners still complaining about hum even after trying 
to follow all of the advice given here.  It's still a valid topic and 
not outside the list boundary rules.


And of course, every single post in this recent KPA500 hum thread has 
been clearly identified in the headline and could be easily ignored or 
deleted by anyone who was able to read it.  You could have done so 
yourself in far less time than it took you to write your post.


Dave  AB7E



On 10/19/2020 9:34 PM, Eric Norris wrote:

The torque spec is called out in the manual.  Why not use a torque wrench?
Can we please not resurrect the KPA500 hum thread already beat to death
multiple times years ago?  Or does everyone need to chime in yet again?

55 inch-pounds.

73 Eric WD6DBM


__
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Elecraft@mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to arch...@mail-archive.com 

Re: [Elecraft] KPA500 Transformer

[Bert]

Agree 100%!!!
Bert VE3NR

On 2020-10-20 8:11, jimn4kh wrote:
I wasn't my intention to resurrect an old thread. I checked the 
archives before posting my message yesterday. I found a little info 
but not much. Perhaps I missed it. I delayed going to the list but 
Elecraft tech support is apparently really backed up because I've 
gotten zero response to my emails and voicemails beyond one email with 
the hum mitigation tech note I mentioned before. I thought perhaps the 
larger community had a specific solution. Judging from the widely 
varied responses I've gotten ovciously not. I've tightened, loosened, 
and moved the transformer around multiple times with no change. I'll 
go get a torque wrench and try that but I cant imagine it resolving 
the problem given how loud it is. Ill take it all apart first and try 
the procedure once and see if it helps. I just dont like having to 
solve problems through expermention on a $2k+ amplifier.

Jim N4KH


Sent from my Verizon, Samsung Galaxy smartphone


 Original message 
From: Eric Norris 
Date: 10/19/20 11:37 PM (GMT-06:00)
To: Bert 
Cc: "elecraft@mailman qth. net" 
Subject: Re: [Elecraft] KPA500 Transformer

The torque spec is called out in the manual.  Why not use a torque wrench?
Can we please not resurrect the KPA500 hum thread already beat to death
multiple times years ago?  Or does everyone need to chime in yet again?

55 inch-pounds.

73 Eric WD6DBM

On Mon, Oct 19, 2020, 9:15 PM Bert  wrote:

> Toroidal transformers cause very little acoustic hum, unless the core
> is not tightly wound or the copper wire windings are loose!
>
> If you have to tighten the mounting bolt with a torque wrench
> to get the transformer quiet, something is wrong!
>
> Bert VE3NR
>
>
>
>
> On 2020-10-19 19:59, Jim Spikes N4KH wrote:
> > Looking for details from anyone who resolved issues with excessive
> > transformer hum during transmit on a KPA-500.
> >
> >
> >
> > I have a hum mitigation application note sent from Elecraft tech 
support.

> > But the procedure recommended is pretty involved - removing front/side
> > panels, un-plugging connections, removing the transformer, changing
> > positions of the rubber discs, and putting it back together. Possibly
> more
> > than once, depending on the results.
> >
> >
> >
> > There is a risk of breaking something, and I'm not sure its going to
> solve
> > the problem if I'm successful. This is a new out of the box KPA500 
kit.

> >
> >
> >
> > If anybody has any lessons learned I would appreciate hearing them.
> >
> >
> >
> > Jim, N4KH
> >
> > __
> > Elecraft mailing list
> > Home: http://mailman.qth.net/mailman/listinfo/elecraft
> > Help: http://mailman.qth.net/mmfaq.htm
> > Post: mailto:Elecraft@mailman.qth.net
> >
> > This list hosted by: http://www.qsl.net
> > Please help support this email list: http://www.qsl.net/donate.html
> > Message delivered to ve...@bell.net
>
> __
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Elecraft@mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to norrislawfi...@gmail.com
>
__
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Elecraft@mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to jimn...@gmail.com


__
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Elecraft@mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to arch...@mail-archive.com 

Re: [Elecraft] KPA500 Transformer

[David Christ]

Torque wrenches are used for two reasons:

1) to make sure things are tight enough

2) to make sure things are not tightened too much.

Stating the proper torque is good engineering practice.  For common screws and 
bolts one can find the suggested torque in reference books and online.  For 
special circumstances the manufacturer should publish the proper values.

David K0LUM

> On Oct 20, 2020, at 5:31 AM, Alan - G4GNX  wrote:
> 
> Then perhaps someone needs to educate Elecraft not to specify use of a torque 
> wrench, in their assembly instructions. ;-)
> 
> 73,
> 
> Alan. G4GNX
> 
> 
> -- Original Message --
> From: "Bert" 
> To: elecraft@mailman.qth.net
> Sent: 20/10/2020 05:15:21
> Subject: Re: [Elecraft] KPA500 Transformer
> 
>> Toroidal transformers cause very little acoustic hum, unless the core
>> is not tightly wound or the copper wire windings are loose!
>> 
>> If you have to tighten the mounting bolt with a torque wrench
>> to get the transformer quiet, something is wrong!
>> 
>> Bert VE3NR
>> 
> 
> __
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Elecraft@mailman.qth.net
> 
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to radio...@mchsi.com 

__
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Elecraft@mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to arch...@mail-archive.com 

Re: [Elecraft] KPA500 Transformer

[Alan - G4GNX]

Then perhaps someone needs to educate Elecraft not to specify use of a 
torque wrench, in their assembly instructions. ;-)


73,

Alan. G4GNX


-- Original Message --
From: "Bert" 
To: elecraft@mailman.qth.net
Sent: 20/10/2020 05:15:21
Subject: Re: [Elecraft] KPA500 Transformer


Toroidal transformers cause very little acoustic hum, unless the core
is not tightly wound or the copper wire windings are loose!

If you have to tighten the mounting bolt with a torque wrench
to get the transformer quiet, something is wrong!

Bert VE3NR



__
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Elecraft@mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to arch...@mail-archive.com 

Re: [Elecraft] KPA500 Transformer

[Eric Norris]

The torque spec is called out in the manual.  Why not use a torque wrench?
Can we please not resurrect the KPA500 hum thread already beat to death
multiple times years ago?  Or does everyone need to chime in yet again?

55 inch-pounds.

73 Eric WD6DBM

On Mon, Oct 19, 2020, 9:15 PM Bert  wrote:

> Toroidal transformers cause very little acoustic hum, unless the core
> is not tightly wound or the copper wire windings are loose!
>
> If you have to tighten the mounting bolt with a torque wrench
> to get the transformer quiet, something is wrong!
>
> Bert VE3NR
>
>
>
>
> On 2020-10-19 19:59, Jim Spikes N4KH wrote:
> > Looking for details from anyone who resolved issues with excessive
> > transformer hum during transmit on a KPA-500.
> >
> >
> >
> > I have a hum mitigation application note sent from Elecraft tech support.
> > But the procedure recommended is pretty involved - removing front/side
> > panels, un-plugging connections, removing the transformer, changing
> > positions of the rubber discs, and putting it back together. Possibly
> more
> > than once, depending on the results.
> >
> >
> >
> > There is a risk of breaking something, and I'm not sure its going to
> solve
> > the problem if I'm successful. This is a new out of the box KPA500 kit.
> >
> >
> >
> > If anybody has any lessons learned I would appreciate hearing them.
> >
> >
> >
> > Jim, N4KH
> >
> > __
> > Elecraft mailing list
> > Home: http://mailman.qth.net/mailman/listinfo/elecraft
> > Help: http://mailman.qth.net/mmfaq.htm
> > Post: mailto:Elecraft@mailman.qth.net
> >
> > This list hosted by: http://www.qsl.net
> > Please help support this email list: http://www.qsl.net/donate.html
> > Message delivered to ve...@bell.net
>
> __
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Elecraft@mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to norrislawfi...@gmail.com
>
__
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Elecraft@mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to arch...@mail-archive.com 

Re: [Elecraft] KPA500 Transformer

[Bert]

Toroidal transformers cause very little acoustic hum, unless the core
is not tightly wound or the copper wire windings are loose!

If you have to tighten the mounting bolt with a torque wrench
to get the transformer quiet, something is wrong!

Bert VE3NR




On 2020-10-19 19:59, Jim Spikes N4KH wrote:

Looking for details from anyone who resolved issues with excessive
transformer hum during transmit on a KPA-500.

  


I have a hum mitigation application note sent from Elecraft tech support.
But the procedure recommended is pretty involved - removing front/side
panels, un-plugging connections, removing the transformer, changing
positions of the rubber discs, and putting it back together. Possibly more
than once, depending on the results.

  


There is a risk of breaking something, and I'm not sure its going to solve
the problem if I'm successful. This is a new out of the box KPA500 kit.

  


If anybody has any lessons learned I would appreciate hearing them.

  


Jim, N4KH

__
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Elecraft@mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to ve...@bell.net


__
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Elecraft@mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to arch...@mail-archive.com 

Re: [Elecraft] KPA500 Transformer

[Macy monkeys]

Even the 'normal' hum was too much my tastes. My KPA500 is now on the floor, 
under the desk with a remote digital readout on the desk. 

John K7FD

> On Oct 19, 2020, at 6:25 PM, Eric Norris  wrote:
> 
> When the KPA500 first came out, there were lots of complaints about hum.
> This made it difficult for Elecraft Support to differentiate between normal
> hum, which I can barely hear, to the obnoxiously loud hum of a misaligned
> transformer.  I finally called support so they could hear the hum of my
> KPA500, which was in the obnoxious category.
> 
> Take a breath, you can fix this.  Tweaking the bolt torque, and slightly
> moving the transformer, requires only removing the cover.  If you don't own
> and can't borrow a torque wrench, given your investment--buy one.  A small,
> inexpensive one will do the trick as the torque is quite low.
> 
> 73 Eric WD6DBM
> 
>> On Mon, Oct 19, 2020, 5:00 PM Jim Spikes N4KH  wrote:
>> 
>> Looking for details from anyone who resolved issues with excessive
>> transformer hum during transmit on a KPA-500.
>> 
>> 
>> 
>> I have a hum mitigation application note sent from Elecraft tech support.
>> But the procedure recommended is pretty involved - removing front/side
>> panels, un-plugging connections, removing the transformer, changing
>> positions of the rubber discs, and putting it back together. Possibly more
>> than once, depending on the results.
>> 
>> 
>> 
>> There is a risk of breaking something, and I'm not sure its going to solve
>> the problem if I'm successful. This is a new out of the box KPA500 kit.
>> 
>> 
>> 
>> If anybody has any lessons learned I would appreciate hearing them.
>> 
>> 
>> 
>> Jim, N4KH
>> 
>> __
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:Elecraft@mailman.qth.net
>> 
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>> Message delivered to norrislawfi...@gmail.com
> __
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Elecraft@mailman.qth.net
> 
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to macymonk...@charter.net 

__
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Elecraft@mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to arch...@mail-archive.com 

Re: [Elecraft] KPA500 Transformer

[Eric Norris]

When the KPA500 first came out, there were lots of complaints about hum.
This made it difficult for Elecraft Support to differentiate between normal
hum, which I can barely hear, to the obnoxiously loud hum of a misaligned
transformer.  I finally called support so they could hear the hum of my
KPA500, which was in the obnoxious category.

Take a breath, you can fix this.  Tweaking the bolt torque, and slightly
moving the transformer, requires only removing the cover.  If you don't own
and can't borrow a torque wrench, given your investment--buy one.  A small,
inexpensive one will do the trick as the torque is quite low.

73 Eric WD6DBM

On Mon, Oct 19, 2020, 5:00 PM Jim Spikes N4KH  wrote:

> Looking for details from anyone who resolved issues with excessive
> transformer hum during transmit on a KPA-500.
>
>
>
> I have a hum mitigation application note sent from Elecraft tech support.
> But the procedure recommended is pretty involved - removing front/side
> panels, un-plugging connections, removing the transformer, changing
> positions of the rubber discs, and putting it back together. Possibly more
> than once, depending on the results.
>
>
>
> There is a risk of breaking something, and I'm not sure its going to solve
> the problem if I'm successful. This is a new out of the box KPA500 kit.
>
>
>
> If anybody has any lessons learned I would appreciate hearing them.
>
>
>
> Jim, N4KH
>
> __
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Elecraft@mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to norrislawfi...@gmail.com
>
__
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Elecraft@mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to arch...@mail-archive.com 

Re: [Elecraft] KPA500 Transformer

[Eric Norris]

Hi Jim,

I had a bad hum from my KPA500 kit, an early model.  Elecraft sent me a new
center bolt that was only threaded on the end--the original bolt had
threads all along the shaft.  Also an additional pad.

Assuming you assembled it all correctly, try these two things:  If you have
a torque wrench, tighten the bolt to the exact spec.  If you don't have
one, try slightly tightening or even loosening the bolt.  Second, make sure
the transformer is exactly centered on the bolt and not touching any of the
sheet metal, including the side panel.  Use a strong flashlight to check it
with the top removed.  UNPLUG THE AMP FIRST!

Mine has been hum-free for years, after the tweaking.

73 Eric WD6DBM

On Mon, Oct 19, 2020, 5:00 PM Jim Spikes N4KH  wrote:

> Looking for details from anyone who resolved issues with excessive
> transformer hum during transmit on a KPA-500.
>
>
>
> I have a hum mitigation application note sent from Elecraft tech support.
> But the procedure recommended is pretty involved - removing front/side
> panels, un-plugging connections, removing the transformer, changing
> positions of the rubber discs, and putting it back together. Possibly more
> than once, depending on the results.
>
>
>
> There is a risk of breaking something, and I'm not sure its going to solve
> the problem if I'm successful. This is a new out of the box KPA500 kit.
>
>
>
> If anybody has any lessons learned I would appreciate hearing them.
>
>
>
> Jim, N4KH
>
> __
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Elecraft@mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to norrislawfi...@gmail.com
>
__
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Elecraft@mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to arch...@mail-archive.com 

Re: [Elecraft] KPA500 Transformer

[Alan - G4GNX]

I don't see the problem. I presume you bought a kit to assemble it 
yourself. You simply reverse part of the assembly procedure, then 
re-assemble it. I've assembled several KPA500s and I'd bet that you 
didn't quite get it right first time. There's no shame in that. This is 
a risk you take with self-assembly. ISTR there's a torque wrench setting 
for tightening. Did you use one?


Have confidence. Take it apart, do as they say and enjoy feeling smug 
that you fixed it yourself. :-)


Lessons learned? Yeah, take your time, follow instructions to the 
letter. Don't do anything if you're tired. Plenty of space. Plenty of 
light. The right tools and a suitable container for parts.


73,

Alan. G4GNX


-- Original Message --
From: "Jim Spikes N4KH" 
To: Elecraft@mailman.qth.net
Sent: 20/10/2020 00:59:06
Subject: [Elecraft] KPA500 Transformer


Looking for details from anyone who resolved issues with excessive
transformer hum during transmit on a KPA-500.



I have a hum mitigation application note sent from Elecraft tech support.
But the procedure recommended is pretty involved - removing front/side
panels, un-plugging connections, removing the transformer, changing
positions of the rubber discs, and putting it back together. Possibly more
than once, depending on the results.



There is a risk of breaking something, and I'm not sure its going to solve
the problem if I'm successful. This is a new out of the box KPA500 kit.



If anybody has any lessons learned I would appreciate hearing them.



Jim, N4KH



__
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Elecraft@mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to arch...@mail-archive.com 

[Elecraft] KPA500 Transformer

[Jim Spikes N4KH]

Looking for details from anyone who resolved issues with excessive
transformer hum during transmit on a KPA-500. 

 

I have a hum mitigation application note sent from Elecraft tech support.
But the procedure recommended is pretty involved - removing front/side
panels, un-plugging connections, removing the transformer, changing
positions of the rubber discs, and putting it back together. Possibly more
than once, depending on the results. 

 

There is a risk of breaking something, and I'm not sure its going to solve
the problem if I'm successful. This is a new out of the box KPA500 kit.

 

If anybody has any lessons learned I would appreciate hearing them.

 

Jim, N4KH

__
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Elecraft@mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to arch...@mail-archive.com 

[Elecraft] KPA500 transformer taps

[Willco Repair/Memory]

Check your house wiring.  The outlet might be wired with 14 gauge wire and
is an extra-long run.  I have about 20ft of 12 gauge wire to the outlets in
my shack and key up is 123.6ac and 74.5dc.  Key down is 122.2 and 62.8.
 
-- 

Jack WA9FVP-  
http://www.willcoele.com/radio_repair 

The Radio Reclamation Center (815) 463-9365
 
__
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Elecraft@mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to arch...@mail-archive.com

Re: [Elecraft] KPA500 transformer taps

[Don Wilhelm]

Ray,

As Phil has indicated, the 10 volt drop in the AC mains may be the only 
problem and should be investigated.  Tracking it down to the trouble 
spot as Phil has detailed is the 'only way to go'.
What I would look for is loose connections (screws) at the breaker box 
and at each receptacle that is connected to that circuit.


If you are capable, remove each receptacle in the circuit and check it. 
If it is wired with the push-in 'backstab' connectors, remove the wires 
and connect them securely under the screws.


There are two types of "backstab" connectors.  One type uses the screw 
to tighten a clamp around the wire.  Those are normally OK, but you may 
want to make certain the screws are tight.
The other type does not depend on the screws, but just have prongs in 
the wire insertion holes to secure the wire.  If you have that type, 
remove the wire (twist while pulling and it will come out) and secure 
the wire under the screwhead.


With that much AC voltage drop under load, you have a condition where 
the failing junction has significant resistance and could cause 
overheating and possibly a fire.


73,
Don W3FPR

On 6/1/2017 12:41 PM, Phil Kane wrote:

On 6/1/2017 8:11 AM, Ray W2RS via Elecraft wrote:


With no load, my AC line voltage is 121 and my power supply voltage
is 73.  With full load, the readings are 111 and 53, respectively.
That is with the yellow transformer tap in place.  Should I switch to
another tap?

As Josh said earlier, be very concerned about the10 volt drop in the AC
voltage measured at the load.  Depending on the "amp-feet" of the
circuity feeding the load, the drop for a 1 KW AC load should be no more
than the industry standard of 2 volts.

  If you have the opportunity, put the amplifier on a dummy load and
measure (CAREFULLY) the AC voltage at the entrance panel, the socket if
it's a duplex one, and the load taps.  This will tell you where the drop
is occurring.  I can't emphasize it more - BE CAREFUL.  As an EE you
know that.


__
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Elecraft@mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to arch...@mail-archive.com

Re: [Elecraft] KPA500 transformer taps

[Jim Brown]

On Thu,6/1/2017 9:41 AM, Phil Kane wrote:

As Josh said earlier, be very concerned about the10 volt drop in the AC
voltage measured at the load.


All great advice. Also, try to trace the wiring that feeds the outlet 
that the amp is plugged into. Possible causes of the high voltage drop 
are 1) conductors that are too small (AWG #14 is the smallest permitted 
for a 15A circuit, #12 for a 20A circuit); 2) bad splices; 3) miswiring 
of outlets or splices (reversals of hot and neutral, or hot and ground, 
or neutral and ground); 4) degraded outlets; 5) miswiring of the KPA500 
power cable (like #3).


For a circuit carrying this much current from an electronic load, wiring 
should be a direct run of #12 (hot, neutral, and ground) from the power 
panel to the outlet. While #12 is not legally required for a 15A 
circuit, the larger conductors reduce IR drop.


AND -- load current to electronic loads is NOT a sine wave, but instead 
consists of pulses at positive and negative peaks of the waveform to 
recharge filter caps in the power supply. This causes IR drop to be 
greater than predicted by application of Ohm's Law to a sine wave. SO -- 
it's good engineering practice to oversize conductors on circuits for 
electronic loads. Two wire sizes is a good rule of thumb.


73, Jim K9YC

__
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Elecraft@mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to arch...@mail-archive.com

Re: [Elecraft] KPA500 transformer taps

[Phil Kane]

On 6/1/2017 8:11 AM, Ray W2RS via Elecraft wrote:
> 
> With no load, my AC line voltage is 121 and my power supply voltage
> is 73.  With full load, the readings are 111 and 53, respectively.
> That is with the yellow transformer tap in place.  Should I switch to
> another tap?
As Josh said earlier, be very concerned about the10 volt drop in the AC
voltage measured at the load.  Depending on the "amp-feet" of the
circuity feeding the load, the drop for a 1 KW AC load should be no more
than the industry standard of 2 volts.

 If you have the opportunity, put the amplifier on a dummy load and
measure (CAREFULLY) the AC voltage at the entrance panel, the socket if
it's a duplex one, and the load taps.  This will tell you where the drop
is occurring.  I can't emphasize it more - BE CAREFUL.  As an EE you
know that.

(Among other things my company designs comm station AC and DC power
installations - if you need help, just ask.)

Ray - contact me directly.  Our paths have crossed way back when..

73 de K2ASP - Phil Kane (since 1952)
Elecraft K2/100   s/n 5402

VP - General Counsel & Engineering Manager
CSI Telecommunications, Inc. - Consulting Engineers
San Francisco, CA - Beaverton, OR
__
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Elecraft@mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to arch...@mail-archive.com

Re: [Elecraft] KPA500 transformer taps

[Josh]

I'd be first concerned with the 10V drop in line voltage. Do you know where 
that's occurring?

73,
Josh W6XU

Sent from my mobile device

> On Jun 1, 2017, at 8:11 AM, Ray W2RS via Elecraft  
> wrote:
> 
> 
> With no load, my AC line voltage is 121 and my power supply voltage is 73.  
> With full load, the readings are 111 and 53, respectively.  That is with the 
> yellow transformer tap in place.  Should I switch to another tap?
> 
> 
> 

__
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Elecraft@mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to arch...@mail-archive.com

[Elecraft] KPA500 transformer taps

[Ray W2RS via Elecraft]

With no load, my AC line voltage is 121 and my power supply voltage is 73.  
With full load, the readings are 111 and 53, respectively.  That is with the 
yellow transformer tap in place.  Should I switch to another tap?


73 Ray W2RS


__
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Elecraft@mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to arch...@mail-archive.com

[Elecraft] KPA500 - transformer low level hum

[Johnny Siu]

Hello Group,
 
When the KPA500 is operating, I notice that the transformer is vibrating and 
gives a low level hum.  Is that normal? Can the hum be reduced?
 
Any ideas?

TNX  73,


Johnny VR2XMC
__
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Elecraft@mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html

Re: [Elecraft] KPA500 - transformer low level hum

[Eric Swartz - WA6HHQ, Elecraft]

This is normal at this power level.
73, Eric

---
www.elecraft.com


On 9/16/2011 7:11 AM, Johnny Siu wrote:
 Hello Group,
   
 When the KPA500 is operating, I notice that the transformer is vibrating and 
 gives a low level hum.  Is that normal? Can the hum be reduced?
   
 Any ideas?

 TNX  73,

 Johnny VR2XMC
__
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Elecraft@mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html