Well, here are some prefect examples for you. I have worked in the radio and audio industry my entire life, and my father and grandfather have before me. So, its not like I am talking out of my ***, and I would say 90% of devices that have a major circuit malfunction have other hidden problems with components because of the stress they go under during the circuit failure, ESPECIALLY if the problem is in the power supply. I have seen it in so many repeaters and pro-audio amps that have blown power supplies, you fix that then the output drivers goes then the rectifier diodes than something else than something else until you have rebuilt the whole thing. Circuits don't blow up with out a cause, and there is the rare case of having a bad transistor or diode starting out but most of them are caused by over heating, a voltage spike, non proper loading of the circuit (user and design error, perfect design case was in some old Klark Teknik DN360 EQ’s one of the tone chips would always over heat and break which had to be changed regularly), and all of that stuff puts stress on all of the components not just the one that was obviously damaged. Another example was in a pro amp, its outputs were blown, so they were replaced easy fix 4 transistors and everything worked tested fine and sounded fine, 3 days later after being reinstalled 2 of the caps which fed the output transistors decided to have a melt down and actually popped. Put a new amp (same model and brand) into the application and it has been running with out problem for 6 years now. Same experience with some Behringer Comp/Gates, MX440’s I think, we have repaired. Simple diodes, everything else checked fine, but a short time after the fix the output circuit lit up. Like I said 90% of the ‘repaired’ devices have either ended up with the same problem or something worse. The devices that have new boards put into them no problems what so ever. And anymore in the Pro-Audio/Home Audio/Radio words new boards are always put in and the old ones get ripped down and retraced and all new parts are put on them (key is ALL). My experience with car audio has been the same. My 12.1 decided to make a nice smoke show, and when I got it back brand new board in side. It was a rebuild board by the way. SO, go a head and repair it and you might have a great amp or whatever for years and years but it’s always still going to be half assed.
