I figured I’d post an update if anyone comes across this. I pulled the working amp out and put it side by side with the broken board and was making good progress probing them with the oscilloscope and writing down the differences I could find, but accidentally shorted something and fried the working amplifier.
At this point I gave up trying to get the original amps working and ordered two Dayton Audio KABD-250 amplifier boards and accompanying power supplies. These are 2 channel boards with DSP, so with some measurements and programming I basically recreated the active crossovers. I 3d modeled some brackets to mount the PSU and amp to the original heatsink, and managed to reuse the original RCA jack as well for input. These look basically completely stock from the outside, though I didn’t bother wiring up the LED. The amp does have a slight 60 hz hum but this may be just some noise induced by running the RCA cables next to power, but it’s also not loud enough to overpower music. I paired it with a KEF KC62 sub and a MiniDSP DDRC-24 for Dirac Live and altogether it’s sounding really fantastic now.
