[Elecraft] [OT] RS-35M noise

[inventor61 .]

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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