Thank you, Allison.? I think I understood that feedback oscillations could be causing the board failures.? I did not have an issue before making the board mods.? I did afterward.? I chalked it up to not having done the SW upgrade before applying power.? I am not sure that was the cause.? I removed and checked the IRFZ24Ns, and they both check out good.
I have noticed that my board has another MOSFET (2n7000) through hole soldered under the board in what looks parallel to Q10.? See attached pictures.
I did some voltage checks, and it looks like Q9 and Q10 are on without the RPi installed; at least, I am getting the 12volts to the bias circuits.? I adjusted the bias controls, and the current went down, so I guess I will need to replace Q9 and Q10.? I will need to order replacements as I do not have either one in my supply.
73
Evan
AC9TU
