Ok, I guess the terminology just threw me off. I presume you just meant to ensure no voltage leakage when testing in diode mode on the bench. There is no voltage leakage. Everything that should not have continuity doesnt, and everything that should, has a solid reading.
At this point, I think I'd leave the SCR out, temporarily (will defeat protection) and test with the audio modules to see if the amp will be worth spending any more time troubleshooting.
Ok, I will give it a shot when I get home. thanks again for your persistence on this. I know this amp definitely isnt worth the time spent on it, but I can certainly state the learning about it is priceless. Much appreciated.
If I leave the SCR out and install the output ICs and put it back together completely, if it works, is there any harm done other than the protection circuit being disabled?
If I leave the SCR out and install the output ICs and put it back together completely, if it works, is there any harm done other than the protection circuit being disabled?
At this point, I simply want to make sure that you have enough good modules to make any more effort feasible.
I don't think I'd use it without protection.
While you have it apart, heat the thermostat to see if that part of the protection is disabled with the SCR out of the circuit.
I don't think I'd use it without protection.
While you have it apart, heat the thermostat to see if that part of the protection is disabled with the SCR out of the circuit.
removed the SCR. put one IC in (didnt want to do both at the same time), powered it up, had both pos and neg rail voltage, then after about ten seconds, pos rail diode shorted. removed shorted diode from circuit. Powered it up again, and neg rail diode started smoking and hot to the touch. shut it down before it shorted.
I am thinking maybe for this test I need to put the full wave rectifier back in? It seems that both voltages likely might have maintained if I was using a more robust diode setup.
I am thinking maybe for this test I need to put the full wave rectifier back in? It seems that both voltages likely might have maintained if I was using a more robust diode setup.
You can try the bridge rectifier but I think it's going to overheat. You need to install high-speed rectifiers if the bridge heats up.
tried original bridge rectifier as it checked out on the bench ok. 5a draw approximately and about 2mvac. Tried the replacement rectifier and got about 60mvac on each rail. rectifier got hot to the touch as well as output IC. Pulled the rectifier out of the circuit and went back to the 1/4w halfwave setup and verified that I still have both pos and neg rail voltage at 33vac. I didnt leave it on too long as I didnt want to cook another diode.
This did occur to me the more I thought about it. Initial testing in the very beginning had this same IC installed. I will swap in a new one tonight and see what I get.
The rail voltage is DC.
I'm not sure what you meant by the voltage you posted in #251.
I think you stated that with either module installed, you get excessive current draw. Is that correct?
I'm not sure what you meant by the voltage you posted in #251.
I think you stated that with either module installed, you get excessive current draw. Is that correct?
I was checking before the diode at the rectifier so I could verify the square wave as well.
Correct. With old and new IC installed in the same position (separately, of course), high current draw and the diode gets hot.
Correct. With old and new IC installed in the same position (separately, of course), high current draw and the diode gets hot.
I don't know how the slow diode would affect the current draw when there is more of a load (from the module). It would drive more ripple to the rail caps when loaded so that could be part of it. Before I'd write it off, I'd try the high-speed rectifiers.