This is a 1966 Supro 6497 "combo tremolo" which is a 2X6L6GC amp, 5U4 rectifier, 3X12ax7 in the preamp one of which is used as a trem tube (both sides).
Originally I thought the OT was bad as I was getting weird readings, however I'm not experienced troubleshooting transformer issues and I may have been making a mistake. I had an extra OT that works perfectly and I stuck that on there, but still... nothing.
Problem: the amp makes NO sound. No hiss, static, nothing. Power on, and I can hear the PT humming very faintly - AC power in is fine, indicator light works, I have all new caps throughout the amp (filter, signal and otherwise), conversion to 3 prong, all grounds test good, rolled all different tubes, used different speakers, disconnected standby (which is just a PI ground to silence it) - still, nothing. Absolutely no sound. ALL voltages everywhere in the amp are where they ought to be - no funky readings anywhere. I tested all the pots and they all seem fine. This is a two channel/4 input amp, no sound no way no how neither channel. It sounds just like the PI is grounded out, but I've checked it a dozen times and it all seems fine. Tubes are not redplating, transformers not getting hot. To ward off parasitics, I put 2.2K stoppers on the leads from the PI (pin 5 power tubes) and I put a 56pf cap across the PI plates. No difference. This amp is cathode bias, no NFB, no choke. I've repeatedly checked for cold joints, continuity etc. I can't get a pop or crackle or hiss out of this amp to save my life no matter what I touch or jumper etc.
THIS IS DRIVING ME CRAZY!!!!! Anyone have any ideas?
Originally I thought the OT was bad as I was getting weird readings, however I'm not experienced troubleshooting transformer issues and I may have been making a mistake. I had an extra OT that works perfectly and I stuck that on there, but still... nothing.
Problem: the amp makes NO sound. No hiss, static, nothing. Power on, and I can hear the PT humming very faintly - AC power in is fine, indicator light works, I have all new caps throughout the amp (filter, signal and otherwise), conversion to 3 prong, all grounds test good, rolled all different tubes, used different speakers, disconnected standby (which is just a PI ground to silence it) - still, nothing. Absolutely no sound. ALL voltages everywhere in the amp are where they ought to be - no funky readings anywhere. I tested all the pots and they all seem fine. This is a two channel/4 input amp, no sound no way no how neither channel. It sounds just like the PI is grounded out, but I've checked it a dozen times and it all seems fine. Tubes are not redplating, transformers not getting hot. To ward off parasitics, I put 2.2K stoppers on the leads from the PI (pin 5 power tubes) and I put a 56pf cap across the PI plates. No difference. This amp is cathode bias, no NFB, no choke. I've repeatedly checked for cold joints, continuity etc. I can't get a pop or crackle or hiss out of this amp to save my life no matter what I touch or jumper etc.
THIS IS DRIVING ME CRAZY!!!!! Anyone have any ideas?
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