[Elecraft] [OT] RS-35M noise

[Rick Bates (WA6NHC)]

I took the easy way out.  A used notepad provided the cardboard which was folded and wedged under the top cover.  Problem solved. 

Rick WA6NHC

Smell Czech correction happens

> On Jun 9, 2019, at 3:24 PM, inventor61 . <inventor61 at gmail.com> wrote:
> 
> Hank
> 
> I am only fabricating new top covers for the 35A size Astron units.
> 
> For the majority of acoustic noise situations in the 35 amp size units (the
> variable and the fixed voltage models) the height of the steel cabinet is
> insufficient to keep the sheet metal of the lid away from the flux lines of
> the transformer.
> 
> The resulting eddy currents decay and 'fight' against the transformer field
> itself.
> This results in the buzzing type hum people experience.
> 
> Over time this vibration can loosen the transformer windings so it can buzz
> by itself.
> But generally, the bulk of the objectionable acoustic noise is from the top
> cover..
> 
> You can confirm the cause by simply removing the cover and operating the
> supply.
> There are only seven screws, as you probably already know.
> 
> Suitable electrical safety precautions are to be taken, of course.
> 
> If you have a 35A Astron unit and by the above method you can show yourself
> that the buzzing/hum noise is a result of the magnetic coupling /
> circulating current scenario I have described, this new composite cover
> will solve the problem - as well as reducing the obvious waste heat from
> the supply.
> 
> Steve KZ1X
> 
>> On Sun, Jun 9, 2019 at 6:17 PM HB <hbjr at optilink.us> wrote:
>> 
>> Some more of the factory cork pieces between the transformer and case
>> fixed mine up – the 50 also.
>> 
>> 
>> 
>> Hank
>> 
>> K4HYJ
>> 
>> 
>> 
>> *From: *inventor61 . <inventor61 at gmail.com>
>> *Sent: *Sunday, June 9, 2019 1:48 PM
>> *To: *lists at w2irt.net; elecraft at mailman.qth.net
>> *Subject: *[Elecraft] [OT] RS-35M noise
>> 
>> 
>> 
>> Peter
>> 
>> 
>> 
>> I now have the prototypes completed of a composite material cover to
>> 
>> replace Astron 35A size power supply covers.
>> 
>> 
>> 
>> This solves the acoustic noise problem.
>> 
>> 
>> 
>> The new cover looks terrific and is a 1:1 swap with the old one.
>> 
>> 
>> 
>> I went through *exactly* the same problem you describe, and then buying the
>> 
>> same replacement supply, then modifying it, ad nauseum, before fixing the
>> 
>> original issue.
>> 
>> 
>> 
>> I expect to be able to produce these (it's done on a CNC machine) in the
>> 
>> coming weeks.
>> 
>> I have several requests already.
>> 
>> 
>> 
>> I do not yet know the cost but it won't be outrageous.
>> 
>> Would this interest you?  It has certainly interested others!
>> 
>> 
>> 
>> 73 Steve KZ1X
>> 
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>> 
>> 
>> 
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