The Fisher 202 - hum problem

[ariekarp]

I have a "The Fisher 202 Futura" receiver, that produces a constant volume hum regardless of volume knob setting.
Any ideas from where the problem stems from?
Thanks

 

[djoffe]

Completely a SWAG from afar, but the first guess on such a symptom would be the power supply filter caps have lost significant capacitance.