Isn't that a serious pain in the butt to take apart and service? Really not the type of thing to make you happy to have to do again.
First, what transistors did you put in it and where did you get them? COunterfeit power transistors are a serious problem these days, and if you buy from these little discount places that send out flyers all the time, be very wary.
SO far I have not gotten any counterfeits from MCM nor from B&D Enterprises
B&D Enterprises - electronics, projection lamps for hitachi, sony, mitsubishi, panasonic, samsung
ANd if you used NTE parts, shame on you.
Otherwise, when you change burnt power transistors, also check the ballast resistors for opens. Ballasts are those power resistors in all the amps of .33 ohms or something similar. "Emitter resistors." Always check the driver transistors, and for that matter the rest of the resistors associated with the output stage.