NSM Output Stage Fault

My NSM jukebox is blowing the fuse on one of the output stages (Part #:171-702).

I have switched the two output stages to confirm that the fault is actually on the PCB.

Inserting a new fuse (4 amp slow-blow) and switching on the jukebox gets the LED on the output stage to light, which indicates everything is okay, but as soon as a CD tries to play, the fuse pops.

Any ideas what I could check or what I should be looking for?

Trace down the fault using the schematic - it shouldn't be too difficult to nail the problem down.
Having two identical boards should make it easy.

Okay, I went through the board component by component and I found a short on two of the Darlington Transistors - everything else seemed to check-out okay.

I replaced the two faulty transistors and switched-on. Happy days, sound from both speakers and sounding great - even though it was Rick Astley!!!

One minute later... BUZZ, POP. Fuse blown again, and this time all four Darlington Transistors are showing shorts????

Does anyone have any ideas what could cause this? Perhaps a complete replacement output stage is the answer?

Replacing JUST the transistors is NOT a proper fix.
The hidden cause could be defective resistors, capacitors, improper biasing? whatever.
Something caused them to blow... find out why - service manual and troubleshooting is mandatory.