On Mar 2, 7:07*pm, "JohnC" wrote:
Thank you all for your assistance and suggestions to help me with this
hum problem. *I opened it up again today and removed the front too to
better inspect connections on the front panel. *With the unit on, I
tapped all over the unit with a non-conductive tool. *I was unable to
have any effect on the hum. *I loosened and tightened many screws.
Especially those that appear to provide some grounding. No change. *I
found no connections that appeared suspect.

I suppose the next step is to test the caps with an ESR meter. *This is
probably beyond my ability and will involve the purchase of such a unit..
So I think I will button the unit up, and for now keep it on 'Monitor'
and use an external tuner on the monitor inputs. *There is no hum when
using Monitor.

Yes this unit is a relic and in fact purchased by my wife new in the
early 70's. *Perhaps not worth the service fee for repair, but it
provides a connection to the past so I'll keep in for her a bit longer.

Thanks again.

John

Was the hum only on the (FM) radio section? That would have narrowed it
down somewhat...

Mark Z.

Mark,
The hum is there for phono, AM, and FM - so all source inputs.
John

Didn't you report earlier that you tried connecting a separate audio
source into the tape monitor inputs and the hum went away? Did you
mean completely, i.e. no hum problem at all in this case? That really
sounds like a (mechanical) grounding problem to me. Especially since
the volume and tone controls worked for this test, which would
indicate that it isn't a problem with preamp/tone power supply
ripple. Good luck.