If you suspect that one of the 1N52xx zeners is defective, pull one leg and re-check. While it's desoldered, read the numbers you couldn't see while it was soldered in the board.
Ok, I've replaced all the parts I found to be bad in the first channel. Both the dc offset and the bias pots appear to work as they should, it's not burning any resistors. So it looks like possible I know what I need to do to finish the other 3 channels. However, I did notice that the 530's seem to run a bit warmer than the 9z34's. Is that normal in this amp?
At idle, the bias current and power dissipation should be the same through both so they should operate at about the same temperature unless there is a different number of the two part numbers. One of the few things that could make a difference is if the rail voltage (positive vs negative) was significantly different.
OK, I thought they should run about the same temperature. I'm not sure what is causing the 530's to warm up more, the rial is pretty centered on +/-27 volts. I would imagine that where ever the power is going should be warming up a component or components shouldn't it? To get the dc offset near 0 the pot had to be turned up higher than I expected.
Perry, thanks for the information and your time answering my questions. The amp is up and running now.
For the output transistors with no load, there really isn't anywhere for the current to flow other than from one bank of output transistors to the other.
Or there is another possibility is of ones one stupidity and a jumper wire sitting under the amp. I need to get a larger more organized work area. The problem has been resolved. Thanks again for your help on this one!
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