Good day to all techs out their , i hope you have great jobs going on. Need your help or tips guys, I am working on a bass amplifier Ampeg SVT-7 pro. I know a lot of techs are having a hard time on this amp ,as i read in some forum as I do. The amp is dead without green light power indicator ON. Upon thorough trouble shooting surprising ly i did not find any defective parts or shorted whatsoever. I suspected on the IC ICE2a165 U2 PWM controller which was getting really hot when powered on, but which I replaced with a higher wattage ICE2a265. The IC is not getting hot as much but still no power indicator and still dead, no response click on the relay REL2 . ANother thing i want to point out is since the TH1 in parallel with the the relay contact has a low resistance its supplying 220 volts ac on the BR1 rectifier. Is this TH1 normal for having a low resistance of 2 OHms? .Can't find any more parts to suspect , if anyone encountered this problem please a small tip might help me. Attached is the schematics.
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I had found 2 IGBT that are open and defective. which is responsible for the +/- 55 volts. On circuit they read nomally by tester because its collector and emitter is in parallel with a diode. If you want to make sure , take it out from the board and check it. I will order this part and will update once i fix it.