Sorry, hit send too quickly....

JohnC wrote:
I sprayed cleaner in the volume control, hum still present. Something
else.. the hum is audible no matter what input is selected from the
input switch, FM, AM, Phono, tape/aux. But there is a Monitor switch and
when switched from Source to Monitor, the hum ceases.

John C.
John,

Have you tried feeding a source into the monitor input and see if the unit
sounds OK? I'm guessing it will. While I don't know the HK-230A, I have
seen receivers that the tape monitor switch feeds the volume control
directly (or nearly so) eliminating the the tone control amps.

I strongly suspect that you have a low level (regulated) power supply
failure that is causing the hum. Looking at the power supplies that feed
the preamp circuits with an oscilloscope is going to be the hot ticket
here.

Tim Schwartz
Bristol Electronics

Tim,
Yes, when I plugged a source into the monitor input there is no hum. All
controls, bass, treble, balance, volume work for the monitor source.
Another item of interest- one of the channels begins to cut out after about
half a minute while using the monitor input. I can unplug the RCA jacks and
reinsert and both channels come back, only to have one of the channels drop
out again after about half a minute.

John


This is starting to sound like the possibility of either bad solder
joints, corroded internal connectors....

Also, it's been reported here that some older stuff develops loose
circuit board to chassis connections which can be solved by merely
backing off and reseating any screws which hold them down.

Clean EVERYTHING--controls, switches, jacks etc. Pull and reseat all
connectors. If the problem still exists, poke around the inside with an
insulated probe and see if you can cause any change in the amplitude of
the hum...or in the case of the tape input, can get the bad channel to
either cut out or in.

Check back....

jak