Bit of a hard question to me, but as far as I can see and understand:
The main chip PIC16F1829 has a 5v signal on pin 18, goes thru some resistors and caps (and branches off to a via I haven't explored), then to a N5551 transistor, that goes to an photocoupler PC817. On the collector of the N5551 it receives 5.59v, which comes from a KA7812 outputting +12v and going thru a 8k ohm resistor. That goes to the SD pin
The thing I'm quite sure about is the photocoupler, further than that it gets more complex
The main chip PIC16F1829 has a 5v signal on pin 18, goes thru some resistors and caps (and branches off to a via I haven't explored), then to a N5551 transistor, that goes to an photocoupler PC817. On the collector of the N5551 it receives 5.59v, which comes from a KA7812 outputting +12v and going thru a 8k ohm resistor. That goes to the SD pin
The thing I'm quite sure about is the photocoupler, further than that it gets more complex
If no one who has a diagram steps in, I'd suggest breaking the circuit that's driving the SD pins high to see if it has a legitimate fault or possibly a defective protection circuit. This will disable the protection circuit so clamp all components tightly to the heatsink before powering up the amp.
While soldering iron heats up, should I also connect the rectifiers fully or still use the lightbulb on one of them?
Has the SD terminal voltage dropped to 0v, with reference to the Vss terminal?
Do you see a square or triangle wave on any terminal of the LM319?
No need to post waveforms.
Do you see a square or triangle wave on any terminal of the LM319?
No need to post waveforms.
If you drive a strong signal into the amp, do you see more signal on the LM319?
Do you have a signal generator?
Do you have a signal generator?
Makes a 50hz square wave on the LM319 inputs and outputs (signal generator making a 50hz sinewave)
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The low-side should have ~10v amplitude. The high-side, may not have much signal. Is that what you're seeing?
Is the amp still in protect mode?
Do you see a rail-rail signal of 50Hz at the input of the output filter inductor?
Do you see a rail-rail signal of 50Hz at the input of the output filter inductor?
It still goes into protect mode and does the whining sound.
Unsure what I need to measure for the rail-rail signal.
Unsure what I need to measure for the rail-rail signal.
Are you starving the amp for current?
What's the DCV across the B+ and ground terminals?
Rail-rail would be measured on the input of the output filter inductor. It would swing between the high and low rail voltage.
What's the DCV across the B+ and ground terminals?
Rail-rail would be measured on the input of the output filter inductor. It would swing between the high and low rail voltage.
12.6v idle, 12.4v when its trying to power on
On the output inductors there isn't much, about a 0.5v 50hz square wave (signal generator still on)
On the output inductors there isn't much, about a 0.5v 50hz square wave (signal generator still on)