trace elliot ta100r intermittent POP

[Mars Amp Repair]

Hello folks,
Intermittently, this amp will POP and you can see the offset as the speakers trust the cones out or in. I have troubleshot down the issue to the power board by disconnecting the input cable to it. There is a black sealed power driver box in the audio power stage that when heated/cooled exacerbates the issue. Has anyone had experience with one of these amps acting this way and/or had any luck trying to procure one of these power modules?
Find Service manual attached.
I guess I'll try to contract Trace (bought by Gibson last I knew) and see what they say.
Thanx, Glen

[Mars Amp Repair]

Update on this Trace amp:
I called British Audio.com to see abt obtaining this Module. Shane there indicated that it is NLA and we need to bypass it. I believe what he was suggesting is to disconnect the module and change the resistor R4 in the negative feedback network from 100K to 470K.
I merely added a resistor in series with R4 by adding a 390K resistor between pins 2 & 3 where the module was connected. It worked just fine.
In retrospect, since the module receives +-16V from the power board, I suppose there is an opamp in that module that conditions the negative feedback somehow or possibly actively controls the NF...who knows.
Whatever, this solved rather than having to tell the customer that the part is NLA, sorry Charlie!