[Elecraft] KPA500 thermal clicks

Thu Jul 19 10:48:51 EDT 2018

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 <rmcgraw at blomand.net> 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: elecraft-bounces at mailman.qth.net [elecraft-bounces at mailman.qth.net] on behalf of Martin Sole [hs0zed at gmail.com]
>>> Sent: Wednesday, July 18, 2018 8:37 PM
>>> To: elecraft at mailman.qth.net
>>> 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
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