Ben, here is a couple pics. As well, there is 2 more here.
https://www.electro-tech-online.com...d-audio-amp-where-should-i-be-looking.110285/
If you want the full rezzy pics, shoot me your email via PM. I very much agree with you that the driver or PS anyway just seems to be a problem and the fact that the mosefets toast instantly points me directly to the driver board BUT how the heck do those mosfets get controlled? By looking at the driver, they surely do not get switched by any type of IC.
If you look at the pics, you will see that I have removed the mosfets along with the heat sink. In the two recent ones, the driver board is out. There is another daughter board that has a glob of epoxy covering something so that might be the mystery IC that is running the show.... However, it does not appear that it has anything at all to do with the mosfet drivers.
On the mosfet driver board, You can clearly see that of the 5 diodes, 2 are marked "Z1, Z2", and the others are Ds. I will assume that only 2 are zeners and the others are ????
markings are
307
0
F4
I am not familiar with them. I am hoping I can find them bad.... Let me know what else you want/need.
I tested all the diodes with a DMM diode test. the "schottky" (??) diodes all test about .5V drop one way and OL the other so I am assuming they are not shorted out. As I understand, that is how you test a schottky, if that is what they are...
In the pics, you can see where the PS ends about where the large coil is and the output stage begins. Just not much going on in the PS and a bunch of stuff has already come of the board for testing. All the resistors, caps, etc have been tested. I did not remove the 2 large, fast acting diode but they test in circuit fine. Basically power comes in, makes its way to the bridge, then over to the mosfets and transformer coil and power cap. From there it goes out into the world. I have also removed several components on the output side for testing and everything is coming back fine.
IMO, I just cannot see a transient making it's way past everything in the PS and taking out the output stage. Amps commonly burn up from overdrive and that usually shorts the the output side. I think this one took a quick surge or possibly is just failed for no good reason. Only thing I have to go on is the PS mosfets are toasting and I do not even know how they work in this circuit....