A few things to check / eliminate _ make sure all interconnect and speaker cables are a good distance away from power cables not alongside or running parallel with .
Same with the tuner ariel . Avoid coiling of excess cabling and try a different cable to connect the tuner and see if it improves,
Is this something that just started happening on the system that was previously ok?
Same with the tuner ariel . Avoid coiling of excess cabling and try a different cable to connect the tuner and see if it improves,
Is this something that just started happening on the system that was previously ok?
do other inputs - CD / turntable, etc work?
If so, and you're using cable company input for FM tuner - via coax cable - could be ground loop from improperly grounded street feed. I had this several times myself, and would occur using either the 75ohm input, or the 300ohm terminals with matching transformer
Most cable providers offer 75ohm coax isolation baluns for this - and they certainly worked for me.
If not, and the hum is present with no signal inputs connected, you've got a problem in the amp. Exactly were to start is a good question
This sounds like the unit still is partially working but has a problem in the preamp section - maybe one of the 4066s used for switching is dead or no longer receives power. If there is a signal source with adjustable output volume floating around (walkman, discman, MP3 player, smartphone or similar) plus matching cabling, I would momentarily unplug the connection between MAIN IN and TONE OUT and run said source into the MAIN IN. If that works fine, theory confirmed.
Presumably the hum was already present before, there seems to be a ground loop problem worth hunting down as well - it is to be assumed that along with the tuner, another of the sources is earthed directly or indirectly. But that's another problem for another day.
As ugly as this receiver is, it's pretty fixable. As long as the power amp is fine (it's an STK based job), there's not too much in terms of rare or exotic parts in the preamp or power supply section. I've got the impression the OP better lug it to a repair guy though, as some further digging with a multimeter will be required to identify the faulty part.
Presumably the hum was already present before, there seems to be a ground loop problem worth hunting down as well - it is to be assumed that along with the tuner, another of the sources is earthed directly or indirectly. But that's another problem for another day.
As ugly as this receiver is, it's pretty fixable. As long as the power amp is fine (it's an STK based job), there's not too much in terms of rare or exotic parts in the preamp or power supply section. I've got the impression the OP better lug it to a repair guy though, as some further digging with a multimeter will be required to identify the faulty part.
me too , contradictory posts and l'm still not sure what the exact issue is although based on the symptoms and the fact that the system suddenly developed the fault tends to suggest failed caps rather than an earth problem especially given it was made in 83/84 .
Ok one more try 
Zips can you describe exactly what happened when the fault first became apparent? Specifically were you using the system and it suddenly started to hum ?
Did the hum change in frequency or stay the same once it started?
Was anything changed on the system? ( cables etc ) Was the system moved to a new location ,room and was it plugged into a different wall socket or extension lead?
lf you unplug the speakers is the hum still heard from the amp itself and with no speakers connected does it still hum using headphones?
Zips can you describe exactly what happened when the fault first became apparent? Specifically were you using the system and it suddenly started to hum ?Did the hum change in frequency or stay the same once it started?
Was anything changed on the system? ( cables etc ) Was the system moved to a new location ,room and was it plugged into a different wall socket or extension lead?
lf you unplug the speakers is the hum still heard from the amp itself and with no speakers connected does it still hum using headphones?
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