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

[Jim Brown]

On 4/24/2020 8:17 AM, Robert Sands wrote:
> My Astron hums loudly only when the fax machine runs. Otherwise silent.
> ?interaction puzzling.

This strongly suggests one or more mis-wired outlets in your home. 
Things like phase (hot) and neutral reversal, neutral and ground 
reversal, or an additional bond between neutral and ground (there MUST 
be one at the power entry panel, but there must NOT be one anywhere else).

I suggest that you start by checking every outlet with a good outlet 
tester.

There's one other thing about Astron supplies that also might be the 
cause -- the green wire is not properly connected to the chassis inside 
the PSU, because the lug to which the green wire is soldered is 
insulated from the chassis by paint. Check for this by measuring between 
the green wire on the plug and the chassis with an Ohmmeter. You should 
see a dead short. If you don't, open it up, scrape the paint under that 
lug. While you're at it, remove the wire between V- and that lug. This 
problem is documented in
http://k9yc.com/PowerSupplyBondingAndAudioDistortion.pdf

73, Jim K9YC