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I don't expect your DC voltages to be a problem at this point, the amp basucally works, we just have added hum in certain parts. That won;t be the result of DC trouble.
By the way, you got +36v on pin 8 and only 14v on pin 7. Just to educate yourself to your meter, try this. Instead of measuring the voltage from pin 7 to ground, measure it from pin 7 to pin 8. Now starting with the 36v on pin 8, you can calculate from this new reading what voltage must be on pin 7. I bet it won;t be 14v.
Normally we think of our meter as an invisible participant. But the meter has an impedance of its own, and that reacts with the circuit, and that causes the artificially low voltage reading on pin 7.
Now back to the issue at hand.
Part of the joy/reward/challenge for me in this effort is the solving of the problem without the amp in front of me. A sort of "Look, Ma, no hands" thing. That said, we may soon come to a point where it is hard for me to get you much further along from afar. My thinking here is that the bypassed signal is hum-free, but the hum is present through the loop circuit by the time it gets to WJ8. SO in my head, the hum is either being picked up by the cable at WJ8 or is coming from pin 6 of the tube. SInce it doesn't seem to be present at the cathode of V3, I would not normally expect it to be at pin6, but we should be able to see it. Scope WJ8, we know the hum is there, so what does it look like? The hum signal probably won;t be very large, but it should be traceable. Once you know what it looks like and how much of it there is, go back to pin 6 of V3 and with the scope on AC, how much hum signal is there? And if we have already tried a different V3, we have have we not?, then there is a llimited space for this to come from.
Q1 is a mute, and it only pulses when you switch channels. Lok bottom center of the page straight down from the send level control. See that little graph with the ;pointy curve on it? That is the "transition mute" waveform, the entire pulse is 60ms long, that is 60/1000 of a second. Your meter won't catch it. All it does is briefly ground off the signal path for a moment when channels are switching. This prevents noises. All other times it sits dormant.
A relay is nothing more than a switch that is remotely actuated. Ther is a magnet coil inside that does that. The switch contacts are uop in the circuit changing circuit paths to suit. The magnet coil is totally separate from that - the whole point of a relay. FInd the little graph again, now look to the left past the two triangles of U2, and you will see K1-C and K2-C. the symbols look like half a transformer. That is the symbol for an iron core coil - the electromagnet in the relay. SO pin 7 of U1b is driving those two coils. WHen it turns them on, the switch contacts for K1 and K2 up in the amp circuit will transfer to the other state.
And look down from those a little and see K3, the EFX LOOP relay coil.
Pots do not control relays. Nothing in the signal path controls a relay, the relays control things in the signal path.
By the way, you got +36v on pin 8 and only 14v on pin 7. Just to educate yourself to your meter, try this. Instead of measuring the voltage from pin 7 to ground, measure it from pin 7 to pin 8. Now starting with the 36v on pin 8, you can calculate from this new reading what voltage must be on pin 7. I bet it won;t be 14v.
Normally we think of our meter as an invisible participant. But the meter has an impedance of its own, and that reacts with the circuit, and that causes the artificially low voltage reading on pin 7.
Now back to the issue at hand.
Part of the joy/reward/challenge for me in this effort is the solving of the problem without the amp in front of me. A sort of "Look, Ma, no hands" thing. That said, we may soon come to a point where it is hard for me to get you much further along from afar. My thinking here is that the bypassed signal is hum-free, but the hum is present through the loop circuit by the time it gets to WJ8. SO in my head, the hum is either being picked up by the cable at WJ8 or is coming from pin 6 of the tube. SInce it doesn't seem to be present at the cathode of V3, I would not normally expect it to be at pin6, but we should be able to see it. Scope WJ8, we know the hum is there, so what does it look like? The hum signal probably won;t be very large, but it should be traceable. Once you know what it looks like and how much of it there is, go back to pin 6 of V3 and with the scope on AC, how much hum signal is there? And if we have already tried a different V3, we have have we not?, then there is a llimited space for this to come from.
Q1 is a mute, and it only pulses when you switch channels. Lok bottom center of the page straight down from the send level control. See that little graph with the ;pointy curve on it? That is the "transition mute" waveform, the entire pulse is 60ms long, that is 60/1000 of a second. Your meter won't catch it. All it does is briefly ground off the signal path for a moment when channels are switching. This prevents noises. All other times it sits dormant.
A relay is nothing more than a switch that is remotely actuated. Ther is a magnet coil inside that does that. The switch contacts are uop in the circuit changing circuit paths to suit. The magnet coil is totally separate from that - the whole point of a relay. FInd the little graph again, now look to the left past the two triangles of U2, and you will see K1-C and K2-C. the symbols look like half a transformer. That is the symbol for an iron core coil - the electromagnet in the relay. SO pin 7 of U1b is driving those two coils. WHen it turns them on, the switch contacts for K1 and K2 up in the amp circuit will transfer to the other state.
And look down from those a little and see K3, the EFX LOOP relay coil.
Pots do not control relays. Nothing in the signal path controls a relay, the relays control things in the signal path.
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