Removing the thought to be good driver card brought the amplifier out of protection and no outputs heated up on that side. So seems that something on the pulled driver card was triggering the protection curcuit. I'll dig into the card or just replace the c1027/A1023 transistors. Or maybe it's one of the A1381/C3503
Looking at this driver board more closely, I see some damage I overlooked before.I will dig up a board and post a pic for side by side comparison. U1 looks like it may need replacing, and the sm cap above the 470 sm resistor doesn't appear to be attached. This is something you may have addressed. If so ignore my comments.I will upload a pic of a board when I dig one up, for side by side comparison
Also, below is my post I copied to point out the resistors and inductors that should be checked along with all of the transistors.
If any of the driver transistors short (A1381,C3503,A1023y,C1027y) these resistors may open up, check all resistors in their path(***This are only resistor values only, when I get a chance I will post the locators for them**2.2,4.7,910,270).Also check the 22uh inductors(L1,L2,L3,L7).
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If this goes on much longer, it may be time to pull the outputs and short the servo op-amp. That should allow testing everything in the amp up to the outputs.
It was another diode 1n4742 on that card. Test 1411 amp Powers up with oscillation on the outputs.
Test 1411?
With both boards in place the amp powers up and there is oscillation on the outputs on both sides, correct?
With both boards in place the amp powers up and there is oscillation on the outputs on both sides, correct?
Yes both sides , it was a bad diode the 1n4742 oscillation and clear audio at the speaker terminal. used new silicone tape and some paste for the thermal. Tidied up a fee other things and should be good once in case. Thanks.
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