OK, here's some of the PM94 amp board pics and also a comparison with the PM95 amp module.
Below is a PM94 board with the mosfets and rail switcher Trs pulled off to repair and clean. Notice the 4 multipin connectors. These are the cause of the PM94 self destructing. The matching sockets on the driver board that is stacked on top need to be carefully cleaned, resoldered and spring re-tensioned.
Here you can see the boards stacked and the pins sitting in their connectors. The PCB also needs to be cleaned of lots of brown glue and/or corrosion from said brown glue.
Close up of the other pins, seated. The rail switching transistors also need to have their soldered legs checked as they are under tension and sometimes the pcb trace can lift- note, it is a double sided trace board.
This is the PM94 and the PM95 boards side by side. Note the single PCB on the PM95, the Mosfets are soldered to twin-width tinned copper pads on the upper side of the PCB and once the legs are formed and soldered carefully, there is no tension on the legs or the PCB. That said, the bias transistor IS under tension, and resulted in a cracked joint and a blown set of Mosfets in this case.
Another comparision of single channel modules, the PM94 has a thicker finned heatsink, whereas the PM95 has a taller heatsink- surface area and dissipation would be similar and both are more than adequate for Class A running.
(PM95) Can you see the problem? Pretty disgusting on a AU$5999 TOTL amplifier. It was like that, from the day it was made- both channels had similar central leg poor placement. The bias/vbe and drivers were soldered and then bent over at the factory, as they mounted the PCB to the heatsink, most leads bent over in a nice curve, but the centre lead didn't- it pushed the thin trace off the PCB and hung there for 20 years without anyone ever knowing. Cost a full set of ultra rare Toshiba Mosfets...
PM95 New Mosfets about to be soldered- see the way they improved the mounting? There is the ability for the legs to expand and contract with a step-bend in them and the tinned plate on the PCB means no more dry joints on the output devices either. Optocoupled Class A switching of bias.
Look at all that yummy copper plate- it's everywhere, the whole amp is covered in it, both the PM94 and the PM95.
Some new Mosfets, waiting to be installed after matching...
Hope that helps.
John