dubwicht

I have a TX-4500 that I dug up out of the attic that turns on but no audio. I can't remember exactly how it happened (if it was from loud music etc) because it was eons ago but remember the amp shutting off abruptly. I don't believe it smoked or not. So at the time I checked the fuse and it was fried! so i replaced it. After i replaced it It fired right back up but with no audio. Ive tried speaker a,b,c and all inputs. I took a look at the inside and it doesn't smell like anything burned and nothing looks burned in fact it's pretty clean! I've herd the transistors could have blown is their a way to check them with a multi reader and can you still get these parts? The one thing i did notice is I left the amp on for about 20 minutes @ a high volume and the hot sinks weren't hot? Anyone?