[Elecraft] Astron RS-35M Hum

[wb6rse1 at mac.com]

Astron RS-35M Hum (and probably other Astrons).

I've found some posts in the archives related to this topic so perhaps a bit OT but hopefully of general interest.

My Astron RS35M developed a hum that increased with increased load. Otherwise working OK but became annoyingly loud.

My solution was to insert a round rubber pad at each of the four mounting screws between the chassis and the transformer.

3/4" OD x 1/4" ID x 1/8 inch thick.

https://www.amazon.com/dp/B0BJPF9QMZ

The hum now is very low. Nothing that would otherwise stand out if I weren't listening for it. And it does not change with load or increased load.

So the problem seems to be mechanical coupling between the transformer and the chassis with the hum amplified when the cover is on the PS. Likely varies with any given batch of transformers. My much older RS-35M exhibits no hum at all even under load.

73 - Steve WB6RSE