Elecraft

KPA500 thermal clicks

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ke9uw

Re: KPA500 thermal clicks

The ticking sound is clearly the resonant aluminum heat sink fins. The mechanical shrinking or expanding is abrupt and resonates the fins much like a tuning fork.
My take on it...

Chuck
Amateur Radio, KE9UW
_____
From: [hidden email] [[hidden email]] on behalf of Martin Sole [[hidden email]]
Sent: Wednesday, July 18, 2018 8:37 PM
To: [hidden email]
Subject: Re: [Elecraft] KPA500 thermal clicks

I think it sounds "orrible!". I'm quite used to the low rumble of the
blower in my Alpha 77D but that ticking would be like Chinese water
torture to me. Listening to an individual tick it does seem to have a
ring to it. Okay the recording was perhaps not the most acoustically
perfect but it certainly does sound as if the ring is from the source
and not any sort of artifact. If it is from the source then I think you
can probably find a way to damp it. First trick will be to identify the
specific source.

I had read other comments about a ticking, always imagined it to be
minimal and essentially unobtrusive but if what you have recorded is
anything like how it sounds sat in front of it then definitely it does
sound pretty bad to me and not just in amplitude but also in its timbre,
pitch, and repetition rate.

Martin, HS0ZED

On 19/07/2018 06:25, ANDY DURBIN wrote:

> I placed my Android phone on top of my KPA500 and made a recording while making a few cycles of FT8 TX/RX. The audio files can be found here:
>
> https://www.dropbox.com/sh/amfy3dz8pgl083n/AAAKi2GYripXyIDjiLpJ2hDwa?dl=0
>
>
> One file is the raw recording. The second has been processed in Audacity to amplify to 0 dB peak. The file starts before the first TX. Next the hum of the transformer can be heard with FT8 modulation in the background from TX moni. As the recording progresses the changes in fan speed can be heard. The click are always well above the fan noise.
>
> I used this recording to perform some spectral analysis of the clicks. I took one sample at the click and another sample of the noise just before the click. I then subtracted the noise from the click and I think I have a reasonable click signature to use as a baseline for evaluating any mechanical changes I make in an attempt to reduce the clicks.
>
> Crank it up and enjoy, especially if you think it's normal.
>
> 73,
> Andy k3wyc
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]

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Chuck, KE9UW

Don Wilhelm

Re: KPA500 thermal clicks

Chuck and all,

The clicking/ticking sound is coming from the expansion/contraction of
the "Z" bracket against its mounting screws. Yes, it may seem to come
from the heatsink, because the Z bracket is fastened to the heatsink and
the sound will conduct to it.
The tightness of the screws may affect the amount of sound you hear.

Those wanting to reduce (or at least alter) the sound intensity may want
to tighten the Z bracket mounting screws a bit after several hours of
operation. To tighten the screws into the heatsink (see page 22 of the
KPA500 assembly manual), you may be able to open the cover of the KPA500
and use a small angled #1 Phillips screwdriver, or you may have to
remove the side panel and move the PA module assembly over. The Z
bracket to case mounting screws are accessible from the bottom (see
assembly manual page 24), so try tightening those first.

73,
Don W3FPR

On 7/19/2018 9:18 AM, hawley, charles j jr wrote:
> The ticking sound is clearly the resonant aluminum heat sink fins. The mechanical shrinking or expanding is abrupt and resonates the fins much like a tuning fork.
> My take on it...
______________________________________________________________
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Clay Autery-2

Re: KPA500 thermal clicks

In reply to this post by ke9uw

Y'all are making me want to find a unit with this "issue" now just so I
can solve the mystery....

IF it is the aluminum fins "creaking" due to rapid thermal
expansion/contraction, one possible/probably solution is a small
Sorbothane damper attached across the fins in an appropriate spot....
Can likely be don without measurably challenging the airflow...

73,

______________________
Clay Autery, KY5G
(318) 518-1389

On 19-Jul-18 08:18, hawley, charles j jr wrote:

> The ticking sound is clearly the resonant aluminum heat sink fins. The mechanical shrinking or expanding is abrupt and resonates the fins much like a tuning fork.
> My take on it...
>
> Chuck
> Amateur Radio, KE9UW
> _____
> From: [hidden email] [[hidden email]] on behalf of Martin Sole [[hidden email]]
> Sent: Wednesday, July 18, 2018 8:37 PM
> To: [hidden email]
> Subject: Re: [Elecraft] KPA500 thermal clicks
>
> I think it sounds "orrible!". I'm quite used to the low rumble of the
> blower in my Alpha 77D but that ticking would be like Chinese water
> torture to me. Listening to an individual tick it does seem to have a
> ring to it. Okay the recording was perhaps not the most acoustically
> perfect but it certainly does sound as if the ring is from the source
> and not any sort of artifact. If it is from the source then I think you
> can probably find a way to damp it. First trick will be to identify the
> specific source.
>
> I had read other comments about a ticking, always imagined it to be
> minimal and essentially unobtrusive but if what you have recorded is
> anything like how it sounds sat in front of it then definitely it does
> sound pretty bad to me and not just in amplitude but also in its timbre,
> pitch, and repetition rate.
>
> Martin, HS0ZED
>
>
> On 19/07/2018 06:25, ANDY DURBIN wrote:
>> I placed my Android phone on top of my KPA500 and made a recording while making a few cycles of FT8 TX/RX. The audio files can be found here:
>>
>> https://www.dropbox.com/sh/amfy3dz8pgl083n/AAAKi2GYripXyIDjiLpJ2hDwa?dl=0
>>
>>
>> One file is the raw recording. The second has been processed in Audacity to amplify to 0 dB peak. The file starts before the first TX. Next the hum of the transformer can be heard with FT8 modulation in the background from TX moni. As the recording progresses the changes in fan speed can be heard. The click are always well above the fan noise.
>>
>> I used this recording to perform some spectral analysis of the clicks. I took one sample at the click and another sample of the noise just before the click. I then subtracted the noise from the click and I think I have a reasonable click signature to use as a baseline for evaluating any mechanical changes I make in an attempt to reduce the clicks.
>>
>> Crank it up and enjoy, especially if you think it's normal.
>>
>> 73,
>> Andy k3wyc
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:[hidden email]
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>> Message delivered to [hidden email]
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
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> Message delivered to [hidden email]

Bob McGraw - K4TAX

Re: KPA500 thermal clicks

Well I really don't have an issue with mine but I did search and learn
about using a Sorbothane damper. Interesting stuff and related
applications.

73

Bob, K4TAX

On 7/19/2018 9:01 AM, Clay Autery wrote:

> Y'all are making me want to find a unit with this "issue" now just so
> I can solve the mystery....
>
> IF it is the aluminum fins "creaking" due to rapid thermal
> expansion/contraction, one possible/probably solution is a small
> Sorbothane damper attached across the fins in an appropriate spot....
> Can likely be don without measurably challenging the airflow...
>
> 73,
>
> ______________________
> Clay Autery, KY5G
> (318) 518-1389
>
> On 19-Jul-18 08:18, hawley, charles j jr wrote:
>> The ticking sound is clearly the resonant aluminum heat sink fins.
>> The mechanical shrinking or expanding is abrupt and resonates the
>> fins much like a tuning fork.
>> My take on it...
>>
>> Chuck
>> Amateur Radio, KE9UW
>> _____
>> From: [hidden email]
>> [[hidden email]] on behalf of Martin Sole
>> [[hidden email]]
>> Sent: Wednesday, July 18, 2018 8:37 PM
>> To: [hidden email]
>> Subject: Re: [Elecraft] KPA500 thermal clicks
>>
>> I think it sounds "orrible!". I'm quite used to the low rumble of the
>> blower in my Alpha 77D but that ticking would be like Chinese water
>> torture to me. Listening to an individual tick it does seem to have a
>> ring to it. Okay the recording was perhaps not the most acoustically
>> perfect but it certainly does sound as if the ring is from the source
>> and not any sort of artifact. If it is from the source then I think you
>> can probably find a way to damp it. First trick will be to identify the
>> specific source.
>>
>> I had read other comments about a ticking, always imagined it to be
>> minimal and essentially unobtrusive but if what you have recorded is
>> anything like how it sounds sat in front of it then definitely it does
>> sound pretty bad to me and not just in amplitude but also in its timbre,
>> pitch, and repetition rate.
>>
>> Martin, HS0ZED
>>
>>
>> On 19/07/2018 06:25, ANDY DURBIN wrote:
>>> I placed my Android phone on top of my KPA500 and made a recording
>>> while making a few cycles of FT8 TX/RX. The audio files can be
>>> found here:
>>>
>>> https://www.dropbox.com/sh/amfy3dz8pgl083n/AAAKi2GYripXyIDjiLpJ2hDwa?dl=0
>>>
>>>
>>>
>>> One file is the raw recording. The second has been processed in
>>> Audacity to amplify to 0 dB peak. The file starts before the first
>>> TX. Next the hum of the transformer can be heard with FT8 modulation
>>> in the background from TX moni. As the recording progresses the
>>> changes in fan speed can be heard. The click are always well above
>>> the fan noise.
>>>
>>> I used this recording to perform some spectral analysis of the
>>> clicks. I took one sample at the click and another sample of the
>>> noise just before the click. I then subtracted the noise from the
>>> click and I think I have a reasonable click signature to use as a
>>> baseline for evaluating any mechanical changes I make in an attempt
>>> to reduce the clicks.
>>>
>>> Crank it up and enjoy, especially if you think it's normal.
>>>
>>> 73,
>>> Andy k3wyc
>>> ______________________________________________________________
>>> Elecraft mailing list
>>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>>> Help: http://mailman.qth.net/mmfaq.htm
>>> Post: mailto:[hidden email]
>>>
>>> This list hosted by: http://www.qsl.net
>>> Please help support this email list: http://www.qsl.net/donate.html
>>> Message delivered to [hidden email]
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:[hidden email]
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>> Message delivered to [hidden email]
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:[hidden email]
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>> Message delivered to [hidden email]
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]

Clay Autery-2

Re: KPA500 thermal clicks

I've solved many an issue with the stuff... Mostly IS/IT related...
building for low sound, high-durability/longevity, but there are many
applications... especially when you start molding it around fasteners...
I've used it in shotgun pads, running shoes, and bicycle seat pads...
happy on all accounts.... but it is at its best when it is used to
isolate/interrupt metallic vibration loops.

73,

______________________
Clay Autery, KY5G
(318) 518-1389

On 19-Jul-18 09:08, Bob McGraw K4TAX wrote:

> Well I really don't have an issue with mine but I did search and learn
> about using a Sorbothane damper. Interesting stuff and related
> applications.
>
> 73
>
> Bob, K4TAX
>
>
> On 7/19/2018 9:01 AM, Clay Autery wrote:
>> Y'all are making me want to find a unit with this "issue" now just so
>> I can solve the mystery....
>>
>> IF it is the aluminum fins "creaking" due to rapid thermal
>> expansion/contraction, one possible/probably solution is a small
>> Sorbothane damper attached across the fins in an appropriate
>> spot.... Can likely be don without measurably challenging the
>> airflow...
>>
>> 73,
>>
>> ______________________
>> Clay Autery, KY5G
>> (318) 518-1389
>>
>> On 19-Jul-18 08:18, hawley, charles j jr wrote:
>>> The ticking sound is clearly the resonant aluminum heat sink fins.
>>> The mechanical shrinking or expanding is abrupt and resonates the
>>> fins much like a tuning fork.
>>> My take on it...
>>>
>>> Chuck
>>> Amateur Radio, KE9UW
>>> _____
>>> From: [hidden email]
>>> [[hidden email]] on behalf of Martin Sole
>>> [[hidden email]]
>>> Sent: Wednesday, July 18, 2018 8:37 PM
>>> To: [hidden email]
>>> Subject: Re: [Elecraft] KPA500 thermal clicks
>>>
>>> I think it sounds "orrible!". I'm quite used to the low rumble of the
>>> blower in my Alpha 77D but that ticking would be like Chinese water
>>> torture to me. Listening to an individual tick it does seem to have a
>>> ring to it. Okay the recording was perhaps not the most acoustically
>>> perfect but it certainly does sound as if the ring is from the source
>>> and not any sort of artifact. If it is from the source then I think you
>>> can probably find a way to damp it. First trick will be to identify the
>>> specific source.
>>>
>>> I had read other comments about a ticking, always imagined it to be
>>> minimal and essentially unobtrusive but if what you have recorded is
>>> anything like how it sounds sat in front of it then definitely it does
>>> sound pretty bad to me and not just in amplitude but also in its
>>> timbre,
>>> pitch, and repetition rate.
>>>
>>> Martin, HS0ZED
>>>
>>>
>>> On 19/07/2018 06:25, ANDY DURBIN wrote:
>>>> I placed my Android phone on top of my KPA500 and made a recording
>>>> while making a few cycles of FT8 TX/RX. The audio files can be
>>>> found here:
>>>>
>>>> https://www.dropbox.com/sh/amfy3dz8pgl083n/AAAKi2GYripXyIDjiLpJ2hDwa?dl=0
>>>>
>>>>
>>>>
>>>> One file is the raw recording. The second has been processed in
>>>> Audacity to amplify to 0 dB peak. The file starts before the first
>>>> TX. Next the hum of the transformer can be heard with FT8
>>>> modulation in the background from TX moni. As the recording
>>>> progresses the changes in fan speed can be heard. The click are
>>>> always well above the fan noise.
>>>>
>>>> I used this recording to perform some spectral analysis of the
>>>> clicks. I took one sample at the click and another sample of the
>>>> noise just before the click. I then subtracted the noise from the
>>>> click and I think I have a reasonable click signature to use as a
>>>> baseline for evaluating any mechanical changes I make in an attempt
>>>> to reduce the clicks.
>>>>
>>>> Crank it up and enjoy, especially if you think it's normal.
>>>>
>>>> 73,
>>>> Andy k3wyc
>>>> ______________________________________________________________
>>>> Elecraft mailing list
>>>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>>>> Help: http://mailman.qth.net/mmfaq.htm
>>>> Post: mailto:[hidden email]
>>>>
>>>> This list hosted by: http://www.qsl.net
>>>> Please help support this email list: http://www.qsl.net/donate.html
>>>> Message delivered to [hidden email]
>>> ______________________________________________________________
>>> Elecraft mailing list
>>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>>> Help: http://mailman.qth.net/mmfaq.htm
>>> Post: mailto:[hidden email]
>>>
>>> This list hosted by: http://www.qsl.net
>>> Please help support this email list: http://www.qsl.net/donate.html
>>> Message delivered to [hidden email]
>>> ______________________________________________________________
>>> Elecraft mailing list
>>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>>> Help: http://mailman.qth.net/mmfaq.htm
>>> Post: mailto:[hidden email]
>>>
>>> This list hosted by: http://www.qsl.net
>>> Please help support this email list: http://www.qsl.net/donate.html
>>> Message delivered to [hidden email]
>>
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:[hidden email]
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>> Message delivered to [hidden email]
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]

ke9uw

Re: KPA500 thermal clicks

In reply to this post by Bob McGraw - K4TAX

Actually I (agree with Don) thought that it’s possibly the z bracket secured to the heat sink and the difference between the two expansions causing the abrupt shifts and resonating the fins.

Chuck Jack
KE9UW

Sent from my iPhone, cjack

> On Jul 19, 2018, at 9:09 AM, Bob McGraw K4TAX <[hidden email]> wrote:
>
> Well I really don't have an issue with mine but I did search and learn about using a Sorbothane damper. Interesting stuff and related applications.
>
> 73
>
> Bob, K4TAX
>
>
>> On 7/19/2018 9:01 AM, Clay Autery wrote:
>> Y'all are making me want to find a unit with this "issue" now just so I can solve the mystery....
>>
>> IF it is the aluminum fins "creaking" due to rapid thermal expansion/contraction, one possible/probably solution is a small Sorbothane damper attached across the fins in an appropriate spot.... Can likely be don without measurably challenging the airflow...
>>
>> 73,
>>
>> ______________________
>> Clay Autery, KY5G
>> (318) 518-1389
>>
>>> On 19-Jul-18 08:18, hawley, charles j jr wrote:
>>> The ticking sound is clearly the resonant aluminum heat sink fins. The mechanical shrinking or expanding is abrupt and resonates the fins much like a tuning fork.
>>> My take on it...
>>>
>>> Chuck
>>> Amateur Radio, KE9UW
>>> _____
>>> From: [hidden email] [[hidden email]] on behalf of Martin Sole [[hidden email]]
>>> Sent: Wednesday, July 18, 2018 8:37 PM
>>> To: [hidden email]
>>> Subject: Re: [Elecraft] KPA500 thermal clicks
>>>
>>> I think it sounds "orrible!". I'm quite used to the low rumble of the
>>> blower in my Alpha 77D but that ticking would be like Chinese water
>>> torture to me. Listening to an individual tick it does seem to have a
>>> ring to it. Okay the recording was perhaps not the most acoustically
>>> perfect but it certainly does sound as if the ring is from the source
>>> and not any sort of artifact. If it is from the source then I think you
>>> can probably find a way to damp it. First trick will be to identify the
>>> specific source.
>>>
>>> I had read other comments about a ticking, always imagined it to be
>>> minimal and essentially unobtrusive but if what you have recorded is
>>> anything like how it sounds sat in front of it then definitely it does
>>> sound pretty bad to me and not just in amplitude but also in its timbre,
>>> pitch, and repetition rate.
>>>
>>> Martin, HS0ZED
>>>
>>>
>>>> On 19/07/2018 06:25, ANDY DURBIN wrote:
>>>> I placed my Android phone on top of my KPA500 and made a recording while making a few cycles of FT8 TX/RX. The audio files can be found here:
>>>>
>>>> https://www.dropbox.com/sh/amfy3dz8pgl083n/AAAKi2GYripXyIDjiLpJ2hDwa?dl=0
>>>>
>>>>
>>>> One file is the raw recording. The second has been processed in Audacity to amplify to 0 dB peak. The file starts before the first TX. Next the hum of the transformer can be heard with FT8 modulation in the background from TX moni. As the recording progresses the changes in fan speed can be heard. The click are always well above the fan noise.
>>>>
>>>> I used this recording to perform some spectral analysis of the clicks. I took one sample at the click and another sample of the noise just before the click. I then subtracted the noise from the click and I think I have a reasonable click signature to use as a baseline for evaluating any mechanical changes I make in an attempt to reduce the clicks.
>>>>
>>>> Crank it up and enjoy, especially if you think it's normal.
>>>>
>>>> 73,
>>>> Andy k3wyc
>>>> ______________________________________________________________
>>>> Elecraft mailing list
>>>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>>>> Help: http://mailman.qth.net/mmfaq.htm
>>>> Post: mailto:[hidden email]
>>>>
>>>> This list hosted by: http://www.qsl.net
>>>> Please help support this email list: http://www.qsl.net/donate.html
>>>> Message delivered to [hidden email]
>>> ______________________________________________________________
>>> Elecraft mailing list
>>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>>> Help: http://mailman.qth.net/mmfaq.htm
>>> Post: mailto:[hidden email]
>>>
>>> This list hosted by: http://www.qsl.net
>>> Please help support this email list: http://www.qsl.net/donate.html
>>> Message delivered to [hidden email]
>>> ______________________________________________________________
>>> Elecraft mailing list
>>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>>> Help: http://mailman.qth.net/mmfaq.htm
>>> Post: mailto:[hidden email]
>>>
>>> This list hosted by: http://www.qsl.net
>>> Please help support this email list: http://www.qsl.net/donate.html
>>> Message delivered to [hidden email]
>>
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:[hidden email]
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>> Message delivered to [hidden email]
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]

Chuck, KE9UW

Martin Sole-3

Re: KPA500 thermal clicks

In reply to this post by Clay Autery-2

I'm of the same mind, though a KPA1500 is more my preference to replace
one of the aging tube monsters here.

Good stuff Sorbothane.

Sorbothane was specifically designed for shock absorption
<https://www.sorbothane.com/what-is-a-good-material-for-shock-absorption.aspx>
and is manufactured to outperform every other material on the market.
What makes Sorbothane the best material for shock absorption?

* It absorbs more than 90% of shock energy and more than 50% of
vibration energy;
* It performs in temperatures ranging from –20° to 160° Fahrenheit
(–29° to 72° Celsius)];
* It performs at frequencies ranging from 10 to 30,000 Hertz;
* It’s damping ratio is 0.344 at 2.34 HZ;
* It doesn’t support bacterial or fungal growth and is relatively
unaffected by industrial solvents such as diesel fuel, kerosene, and
hydraulic fluid;
* It has an extremely long shelf life; and
* It has a superior damping coefficient.

But I wonder about that temp rating :-)

On 19/07/2018 21:01, Clay Autery wrote:

Elecraft mailing list

Re: KPA500 thermal clicks

It would be interesting to follow the temp rise profile with the ticking. Since the ticking continues over different operating conditions, it is hard to tell if the overall ticking is tracking the temp. Seems to sound the same throughout.. I don't like it at all. Too much thermal resistance differential. Not good..
Mel, K6KBE

From: Martin Sole <[hidden email]>
To: [hidden email]
Sent: Thursday, July 19, 2018 8:45 AM
Subject: Re: [Elecraft] KPA500 thermal clicks

I'm of the same mind, though a KPA1500 is more my preference to replace
one of the aging tube monsters here.

Good stuff Sorbothane.

Sorbothane was specifically designed for shock absorption
<https://www.sorbothane.com/what-is-a-good-material-for-shock-absorption.aspx>
and is manufactured to outperform every other material on the market.
What makes Sorbothane the best material for shock absorption?

* It absorbs more than 90% of shock energy and more than 50% of
vibration energy;
* It performs in temperatures ranging from –20° to 160° Fahrenheit
(–29° to 72° Celsius)];
* It performs at frequencies ranging from 10 to 30,000 Hertz;
* It’s damping ratio is 0.344 at 2.34 HZ;
* It doesn’t support bacterial or fungal growth and is relatively
unaffected by industrial solvents such as diesel fuel, kerosene, and
hydraulic fluid;
* It has an extremely long shelf life; and
* It has a superior damping coefficient.

But I wonder about that temp rating :-)

On 19/07/2018 21:01, Clay Autery wrote:

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Bill K9YEQ

Re: KPA500 thermal clicks

In reply to this post by john@kk9a.com

I own(ed) both. I operate SSB and not continuous modes. No clicking, no fan issues. My hearing is good, yes the fans operate. My THP 2.5KFx had much louder fan noise while rag chewing than the KPA1500. If you are operating in full cycle mode with these lighter weight amps you will have some compromises. Portability/weight was my love for the Elecraft amps not to forget the seamless, and to me, near flawless operation.

73,
Bill
K9YEQ

-----Original Message-----
From: [hidden email] <[hidden email]> On Behalf Of [hidden email]
Sent: Thursday, July 19, 2018 6:30 AM
To: [hidden email]
Cc: [hidden email]
Subject: Re: [Elecraft] KPA500 thermal clicks

Nice documentation. My KPA500 also makes this clicking noise so I would say that your amp is functioning normally. Apparently many people on this list do not find it objectionable. My KPA500 is just a backup / casual use amp but I would still send it in if there was a mod to fix this. I wonder if the KPA1500 also clicks?

Back to the vanity callsign net...

John KK9A

ANDY DURBIN K3WYC wrote:

I placed my Android phone on top of my KPA500 and made a recording while making a few cycles of FT8 TX/RX. The audio files can be found here:

https://www.dropbox.com/sh/amfy3dz8pgl083n/AAAKi2GYripXyIDjiLpJ2hDwa?dl=0

One file is the raw recording. The second has been processed in Audacity to amplify to 0 dB peak. The file starts before the first TX. Next the hum of the transformer can be heard with FT8 modulation in the background
from TX moni. As the recording progresses the changes in fan speed can
be heard. The click are always well above the fan noise.

I used this recording to perform some spectral analysis of the clicks. I took one sample at the click and another sample of the noise just before the click. I then subtracted the noise from the click and I think I have a reasonable click signature to use as a baseline for evaluating any mechanical changes I make in an attempt to reduce the clicks.

Crank it up and enjoy, especially if you think it's normal.

73,
Andy k3wyc

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Eric Swartz - WA6HHQ

Re: KPA500 thermal clicks

Administrator

In reply to this post by ANDY DURBIN

Folks - please see my post just prior to this noting this is normal on the amps.

And in the interest of relieving email overload for others, let's close this
thread at this time.

73,
Eric
/elecraft.com/

On 7/18/2018 9:11 PM, ANDY DURBIN wrote:

> "I doubt that a phone recording has the proper range to qualify as a test device."
>
>
> I think some people have misunderstood the reason for making the recording. The purpose was to establish a baseline. If any mechanical changes I make change the acoustic signature of the clicks then I have increased my knowledge of what causes them. It does not matter a bit if what the phone records represents what I hear.
>
>
> I do not claim that the phone recording is an absolute measurement of anything.
>
> 73,
>
> Andy, k3wyc
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ANDY DURBIN

Re: KPA500 thermal clicks

In reply to this post by ANDY DURBIN

"it is hard to tell if the overall ticking is tracking the temp"

It's quite instructive to view the file in Audacity. That shows clearly that the groups of clicks that happen during the heating cycle are about half the amplitude of the group of click that happen during the cooling cycles. The fan speed gives a indication of PA temperature. Although I normally record PA temperature and fan speed my logger was not running when this audio file was recorded.

This morning I removed the top cover and placed two thicknesses of Scotch double sided foam mounting tape on the top cover half way between the back and the vent holes. This presses on the heat sink fins and reduces the ringing a bit. I found I could still excite the fins by plucking them with a tooth pick inserted through the air holes.

Subjectively the clicks seem to have less ring to them but I need to refine my spectral analysis technique to be sure what difference it actually made. I see no reason that dampening material couldn't be place on top of all the fins except those directly under the air vent holes.

More to be done but it appears that ringing of the heat sink contributes to the problem. Next step will be to find out what excites the heat sink and eliminate if possible. I know it has been stated that it's movement between Z bracket and heatsink but I need to find out for myself.

For those with a concern about my priorities - both this investigation and my Arduino coding are done while watching 6 m for an opening (CT and EA worked from AZ yesterday).

73,

Andy k3wyc

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Clay Autery-2

KPA-500: Mitigating Thermal Expansion Generated Noise

In reply to this post by ke9uw

OK.... I don't have a KPA-500 to take apart and play with, but I just
spent about an hour reviewing the images in the assembly manual, et al.

Yep.... It is likely the thermal expansion and contraction of the
relatively thin aluminum Z-bracket. The Z-bracket appears to be acting
as a heat sink/spreader/connector between the 4 each rectifiers and the
heat sink. There are a NUMBER of potential issues in this setup that
may be causing the noise via thermal cycling:

1) In high demand conditions, the rectifiers are dumping a sufficient
amount of heat into the Z-bracket to cause the aluminum to increase in
temperature enough to expand just the amount required to "tink" during
thermal cycling.... because...
2) The Z-bracket is relatively thin...
3) The Z-bracket is constrained from expansion top to bottom by its
connection to the top and bottom of the chassis.
4) The rectifiers are secured to a "tab" that sticks out of the end of
the Z-bracket that is NOT constrained from expansion in either the
top/bottom or side/side directions. It reminds me of the little metal
tabs in old thermostats designed to change position with temperature in
order to switch conditions on the thermostat... also reminds me of the
temperature activated auto-resetting circuit breakers....

The heat imparted to that tab by the rectifiers causes the aluminum tab
to heat up and expand.... that movement is transmitted to the rest of
the Z-bracket.... the Z-bracket is constrained by its connections to
the top/bottom chassis plates, AND in a thin row to the heatsink... The
unequal distortion of the thin metal produces a sound under thermal
cycling...

There are a NUMBER of factors that may have prevented this.... Thicker
material in the Z-bracket would have provided more rigidity that MAY
have allowed it to resist the distortion events long enough to smooth
the thermal cycling.... More importantly, there would have been more
thermal mass to spread the heat dump from the rectifiers. But we can't
do anything about that part.... but perhaps some mitigation (see below).

The rectifier Z-arms could have been extended to include the rectifier
tab so that it wasn't a small/thin aluminum tab floating in space taking
heat hits from 4 rectifiers....

The Z-bracket has a relatively small thermal connection to the
heatsink... Had the contact patch between the Z-bracket and heat-sink
been larger, the heat load MAY have been able to disperse into the
heatsink fast enough to reduce the thermal distortion sufficiently to
eliminate the sound under high demand through the rectifiers....
maybe. (IAW... attached to a FIN face, rather than the base strip)

Other factors I won't address at present.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Mitigation:

OK... there are a number of things that might be tried to mitigate and
perhaps eliminate the sound... The bottom line (I think) is that we
need to provide a better thermal pathway for the heat from the
rectifiers THROUGH the Z-bracket to SOMEWHERE ELSE at a rate that will
prevent the Z-bracket from distorting to the "tink point". <smile>

1) Connections to the chassis: The chassis has the largest relative
contact patch with the Z-bracket, and has thermal mass that opens to the
exterior for heat rejection. IF we can improve the thermal conductivity
of the interface between the Z-bracket arms and the chassis panels, we
can INCREASE the rate and magnitude of the heat dump into the chassis
panels. The idea is already to provide continuity between the Z-bracket
arms and the top/bottom panels since the paint is masked to provide a
metal to metal contact. It also attached to the rear panel at two
points as well... Here are some things that can be done to increase the
thermal conductivity between the Z-bracket and the chassis panels.

a) Reduce the interface gaps at top, bottom, and rear attachment
points. How smooth is the aluminum plate on the arms and rear mounting
bosses? How flat is it? One MIGHT consider lapping those areas FLAT
and SMOOTH with a true surface/fixture and progressively finer wet/dry
sandpapers to a grit size of 1500 or so... This WOULD require
disassembly of the amp such that you could work on the Z-bracket by
itself. And lapping the areas flat requires that you be able to do so
squarely.... likely requiring a fixture. I would do this. But I've
been lapping processor cases and heatsinks flat for many years.

b) Further improve the interfaces both thermally and electrically by
making sure the corresponding areas on the chassis panels are smooth and
"bright" (no paint, tape residue, overspray, or any other
contaminant.... I would wet sand these areas with a small block and
progressively fine grits of sandpaper or polishing compound... Must be
careful to keep the run-out minimized along the long axis of the Z-arm
contact patches, et al.... I don't see whether the paint is masked off
on the rear panel at all.

c) Finally, these areas should be cleaned WELL with 91%+ alcohol or
other suitably low-residue solvent to get them super clean.... think,
mounting a heat-sink. THEN, on reassembly, you want to use a QUALITY
thermal compound..... Arctic Silver 5 would be almost ideal. IDEALLY,
you would use an electrically conductive thermal compound, BUT because
in this case, we are just "gap filling" to increase the contact patch
integrity, it will still be electrically connected at the SAME points it
would have without the compound. AND the compound will keep the bright
aluminum form oxidizing over time.

2) Connection to the heatsink: The thin strip/patch where the heatsink
mates with the Z-bracket is IMPORTANT. This is the only path for heat
to effectively travel from the rectifiers to the heatsink where it can
be rejected via airflow from the fan to the outside world. Using the
techniques above similarly.

a) Lap the z-bracket face that contacts the heat-sink flat and smooth to
1500 grit minimum.

b) Lap the EDGE of the heat-sink flat and smooth to 1500 grit minimum.
This removes the "black" anodizing layer and provides a full and bright
aluminum to aluminum thermal interface between the heatsink and the
Z-bracket which SHOULD similarly increase the efficiency of heat removal
from the rectifiers/Z-bracket. NOTE: The heatsink is part of the
PRE-assembled PA module.... If you do this, you MUST be careful to NOT
contaminate or damage the PA modul board, traces, components et al with
lapping wastes. DO SO AT YOUR OWN RISK.

c) Properly clean both surfaces and apply the same thermal compound at
this interface joint. Use ENOUGH to provide full coverage, but not so
much that you have excessive squeeze out.... clean up the excess around
the edges with q-tips and paper towels... Do not use alcohol as you
don't want it to wash out the thermal paste at the edges or undercut the
interface connection.

3) Sound/vibration absorption/conversion: We can't just go hog wild and
stuff the box full of dampers and sound absorption material. We don't
want to reduce the interior free volume any more than absolutely
necessary, and for SURE do not want to jeopardize the air flow over the
heatsink and out via the fan opening.

I suggest using a layer of Sorbothane 1-side PSA sheeting of the
appropriate durometer and of sufficient thickness to absorb any
vibration/sound from the Z-bracket that might be made during a high
demand thermal cycle...
The sheeting should ONLY be applied on the torroid side of the Z-bracket
so as not to interrupt/block that last airflow channel between the
Z-bracket and the first heatsink fin. The more area that is covered the
better.... with the trade-off being that you are consuming interior free
volume. The area on the free-floating rectifier tab is of particular
importance.... the area between the rectifier board and the tab should
be fully populated to the end, around the stand-offs and to within about
and 1/8' (or closer if you are good) of the mounting patches of the
rectifiers making SURE NOT to interfere with the rectifier packages
making full contact with the bracket. You probably can't do a
continuous section on the other side of the rectifiers and past the
torroid.... and probably should not try... the torroid appears to be
very close to the bracket at the tangent point of the torroid.... and
perhaps a 1/4" channel left for aiflow would be better.... We don't
want to cause any flow short circuits that would produce stagnant air
that will heat up and work against our purposes.

You could also put a 1/8" thick sheet strip on the non-mating sides of
the Z-bracket ears/arms....

AND one MIGHT consider a 1/8" sheet on the interior top panel (and
bottom though the area is probably not sufficient for the trouble/small
additional gains).

As an aside and not related really.... There is the POTENTIAL that the
40-wire flat ribbon cable could be split and bound into a "rounded"
cable, but I would NOT do that without first thoroughly reviewing the
schematics and examined the signal arrangements.... there may be
signals that need to be separate by intervening grounds on the flat
cable.... We addressed this in the old days when I built 8 foot long
PATA cables with 10x CAT-5 runs by giving EACH signal it's own twisted
pair partner ground. The only benefit to this would be to improve
airflow in/around where the ribbon cable sits.

4) Other thoughts: My original suggestion to put a Sorbothane damper
across the heatsink fins in some fashion to break the resonance of the
sound transmitted to them.... while perhaps offering some mitigation, is
likely not needed if the above is done and may well reduce efficient
operation of the heatsink and airflow. IF I did this, I think I would
likely try some small diameter disks just thick enough to offer an
interference fit, and insert them between fins on the front, top corners
of the fins.

==========================================================================

Without a unit to examine, this is my best, first SWAG at this... I
could be completely off base. But I think this is a good start. There
are a number of additional things that could be done.

I have to say though.... I am overall very, VERY impressed with the
package as illustrated. Getting what they got into THAT package and
making it do what it does is a testament to fine engineering!

If anyone has a KPA-500-K they want assembled, I would LOVE to have the
opportunity to put one together.... my way. <big smile>

73,

______________________
Clay Autery, KY5G
(318) 518-1389

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