Hey guys I have been working on a power 1100a2 amp that someone got a hold of before me. After repairing all the damage they started I ended up replacing all the powersupply fets and all the audio outputs for both channels. I rebuilt the left channel driver circuit also. Only one channel burned out but both sets of powersupply fets and resistors were burned. I powered the amp on with the bias fully counterclockwise and the draws about 8 to 10 amps. The channel that had burned out had about 63v and the channel that had no problem was around 72v. The right side powersupply fets are starting to get warm also. I adjusted the bias on both channels with no effect. Any ideas fellas before I start digging through the driver circuits again?
Okay Perry thanks I will change the gate resistors. Unfortunately i can not check the waveform again because my fluke 97 will not boot this morning. It's been limping along for a while now. I did find one bad output that I replaced. Maybe it was heated too long during install. Checking a few more...
There's a problem with these amps that can make it destroy outputs if there is even a minor problem. The problem is that it charges the huge bank of capacitors and then switches on the biasing for the outputs. If there is a problem, the outputs have to try to pass all of the stored energy. This generally causes the outputs to fail. If you short Q11 collector to emitter, it will force the biasing on full time so a limiting resistor can help protect the outputs. Without the jumper, the limiting resistor can only protect the power supply FETs.
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