[Heathkit] HW-16 and "hum".

[Kenneth G. Gordon]

Hmmm...well, it turned out NOT to be hum after all. Something, 
which I still haven't figured out, was breaking down at a 60 Hz. rate, 
showing very sharp positive and negative pulses at that rate.

One of our list members suggested that I use a spare electrolytic 
cap with the negative clip-leaded to ground and parallel those caps 
that I could in order to check the filter caps.

Doing that didn't make any difference.

HOWEVER, when I shorted the charged up cap's positive lead 
against the chassis, the "hum" immediately went away.

Now get this: the negative lead of the cap is connected directly to 
the chassis. The cap is charged up when I connect it in parallel with 
the various power supply caps. When I discharge that cap by 
shorting its positive lead against the chassis, within about 1/2" of 
the negative lead connection, the "hum" goes away, permanently 
for now.

I'm still clueless....

Ken W7EKB