A few months back I recovered an old NAD 3020A from my father's garage. Hooked it up and all works well aside from a fairly loud humming noise coming from both the loudspeaker and the headphone connections.
The hum in question is not affected by the tone controls or the volume knob (unless the phono channel is selected). It's also substantially quieter when the amp is initially powered on thanks to the muting circuit. The only thing removing the pre-amp jumpers does is stop the muting part.
After doing some searching I came to the conclusion that the problem was with the four big caps in the middle of the board and possibly the two at the back right. So I bought and soldered in replacements, powered it up, and there was absolutely no difference. This has left me out of ideas short of replacing more of the caps (which I plan on doing regardless).
Any bright ideas? I'll attach a picture of the amp in question. The black caps are the ones I put in this evening.
The hum in question is not affected by the tone controls or the volume knob (unless the phono channel is selected). It's also substantially quieter when the amp is initially powered on thanks to the muting circuit. The only thing removing the pre-amp jumpers does is stop the muting part.
After doing some searching I came to the conclusion that the problem was with the four big caps in the middle of the board and possibly the two at the back right. So I bought and soldered in replacements, powered it up, and there was absolutely no difference. This has left me out of ideas short of replacing more of the caps (which I plan on doing regardless).
Any bright ideas? I'll attach a picture of the amp in question. The black caps are the ones I put in this evening.