[Elecraft] OT: Astron RS-35M Transformer Hum

[David Bunte]

David -

I have an RS-35M, that sits on a shelf under my operating desk. I leave it
on 24/7, and never gave any thought to acoustic hum from it. I just ducked
my head down below the desktop, and 'thought' I could hear some hum. I
turned off the power supply and verified that there is a little bit that I
could detect. I am blessed with better than average hearing for a
76-year-old, but that is largely thanks to my hearing aids.

In the past I have had pretty bad hum from power supply transformers, and
the worst case I ever had was totally cured by tightening the bolts that
held the laminations together. That was pretty easy because it was an open
frame transformer in a home brew KW amp. In a number of transformers I have
paid attention to in the past few years, the screws or bolts that hold the
transformer to the chassis go through the corners of the laminations, and
tightening those may also help.

I have been "told" that acoustic hum is often made more evident because the
chassis is vibrating... and that putting some dampening material (a sheet
of rubber for example) under the transformer goes a long way toward
reducing the problem.

Best of luck.

Dave - K9FN



On Fri, Apr 24, 2020 at 10:14 AM David Herring <david.n5dch at gmail.com>
wrote:

> Does anyone have a way to dampen the physical hum generated by the
> transformer in an RS-35M PS?
>
> This really is just transformer hum I’m hearing, not signal hum…my station
> is fully bonded and as a result quiet in that regard.  Most folks probably
> never hear this hum, but I have been “blessed” with really good hearing and
> so this hum irritates the dickens out of me.
>
> If push comes to shove, I will relocated the PS farther away from the
> operating position, I just didn’t want to have to extend power and bonding
> runs and thus am hoping someone has a different idea.
>
> Thanks & 73,
> David N5DCH
> (Formerly AH6TD)
>
>
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