harman/kardon pm645

[admin_exported]

Hi this is my first post here, My old sansui a700 started to intermittently loose one channel, so as money is tight at the moment I looked on e-bay. After missing out on loads of amps I finally won a harman/kardon pm645. A four hour round trip and I had it home to find it also is missing one channel. Taking it apart I find a blown transitor, so I have now ordered a new transistor but my worry is that I don't know why it blew in the first place and I keep reading little notes about 'protection circuitry' that makes it difficult to repair. Can anyone throw some light on this please?

Steve

 

[Anonymous]

Update time: I have now fitted the transistor (I ordered two, one cheap the other more expensive) and it works but there is some background noise mainly on the repaired channel that sounds like the volume control is dirty i:e the noise is at it's worst when adjusting the volume. Anyway i am going to try the other transistor tomorrow in case it is just transistor noise from a cheap item.