How about the other power supply voltages, +/-40V, +/-35V, +/-15V ?
Amp powers on and fuse holds but no sound from the speakers. CLIP light at INPUT emits steady yellow, fan is not working, pressing the TUNING MUTE does not light its red LED. POWER/PROTECT light at POWER switch should be blue, but instead emits steady red and does not change colors under any conditions thus far.
0.00 VDC at speaker outputs
0.001 VDC on FX Send
0.002 VDC on FX Return.
Injected signal into INPUT, get signal at TUNER OUT on patchbay, but no signal from FX SEND jack.
Injected +4 signal into FX RETURN jack and get no sound from power amp to speakers.
On the power amp board, someone has replaced D7 at one point as evidenced by it standing off the PCB by the full length of its leads. Measured 87.0 VDC across D7 in one direction and -86.9 VDC in the other direction. Can hear audible amplifier noise through power amp to speaker when measuring D7 with amplifier on.
UPDATE: Received current schematics from GK which cover this board revision. Correct schematics attached
Make sure to check out the updated schematics attached below.
OK, we have power supply voltages out of whack all over the power amp. Since I have a number of measurements, this is a great opportunity to learn to organize it effectively in a post so its easy to follow for those helping out. Feel free to tweak my data organization, or lack thereof.
We have +86V at R70 (expected +86V)
We have -86V at R71 (expected -86V)
We have +40V at R70 (expected +40V)
We have -40V at R71 (expected -40V)
We have +40.3V at R78 (expected +35V)
We have -35V at R75 (expected -35V)
We have -40.1V at junction of pin#1 of Q20, R41, R36, R40, R44 (expected +15V)
We have -38.6 at junction of pin#3 of U4, R73, and neg side of C33 (expected -15V)
DC MEASUREMENT POINTS
Component ___________________ Expected _________ Measured
Across R15 _______________________ 2.6V _______________ 0.013V
Across R16 _______________________ 2.6V _______________ 0.018V
Across R24 _______________________ 2.1V _______________ 0.000V
Across R33 _______________________ 1.55V _______________ 0.000V
Junction D7, pin#2 Q14, D9 __________ 4.9V ______________ -0.001V
Junction D5, pin#2 Q11, R25, D11 _____ 4.9V ______________ -0.001V
Presumably, you have 40V supplied to U5 since it's there on R78, but check it right on the leg of the regulator. You could have cracked solder or a burnt trace. Also, what are the other voltages right on that +15 regulator (U5)? Obviously, there's something radically wrong with voltages in that +-15v regulator circuit. Also wondering if we have a burnt or missing ground there somewhere.
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