What work have you done to this amp?
Post the DC voltage on all pins of that IC.
U21
Pin 1: 8.76 vdc
Pin 2: .771 vdc
Pin 3: 8.18 vdc
Pin 4: -0.029 vdc
Pin 5: 4.99 vdc
Pin 6: 8.21 vdc
Pin 7: 1.230 vdc
Pin 8: 9.64 vdc
I checked the drive circuit and all looks very nice, very nice crisp square form, and checked the ohm readings between first and last gate legs in all pairs all read 20 ohms.
Checked ohm reading from last leg of Q101 to positive speaker terminal, and it read 0.1 ohms. Wiggling the output inductor coil makes no change.
I checked the waveform on pins 1 and 7 of Ull and they are identical like a heart beat on the EKG again, no triangle or square like they shouls be.
So far thats all I have done i was going to run a sine wave and look at the output signal on pin 1 of U4 but have not got that far.
The board looks like new no dust, no repairs, absolutely immaculant.
You're missing the negative regulated voltage. I think the regulator is the one labeled Q16.
Ok I dont remember checking it on the other amp. I will look for Q16, you need the dc voltage reading from Q16??
Leg 3 of the 337. The 317 is the positive regulator.
Any particular probe configuration?
Black probe on amp ground. Red probe on the regulator.
Ok thats what I thought so the source leg of that regulator started at -0.075 vdc and bled down rapidly to - 0.031 vdc and seemed to hold there.
There's no 'source' leg. Leg 3 is the output. What is the DC voltage on the other two legs?
Leg 1: -0.032 vdc
Leg 2: -18.75 vdc
Leg 3: -0.032 vdc
It's difficult to determine if it's being overloaded or defective so I'd recommend replacing it.
No problem I have several hundred of each in stock, shall I replace both the positive and negative regulators since they are both getting hot?
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