I'm not sure this is part of the answer to the problem with the buzz,
but I think it's worth mentioning again to pass along to the folk.
The bleeder resistor arrangement in this power supply is problematical.
If you are not dead on when mounting the resistors so the screw centers
in the center of the ceramic, it can lead to shorting out. The design
calls for
such an arrangement, and correctly reinstalling the mica insulator/ spacers
between the mounting bracket and the resistor.
I had a devil of a time with a buddy's amplifier until I got some nylon
washers
and screws to lift the mounting brackets off chassis ground. Using mica
spacers
and depending on alignment is not a good idea, IMHO. The breakdown of
the resistor
spacing is too close for comfort.
Been working like a charm, only cost a couple of resistors that flashed
over to
help with the prototyping.
Good Luck, We're All Counting On You!
ed K0KL
One more thing, use fiberglass tape on the screw prior to mounting.
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