When replacing power transistors is it wise to replace just the one that failed such as a PNP transistor or should all of the PNP transistors be replaced? and what about the NPN transistors. Even though they all test good should they be replaced as well? Would replacing just one or one set of either NPN or PNP set up a bias that could cause an unbalance? I’m replacing a 2sb541 with a MJ15025G
I think that really boils down to the circuit and its application. I just went through one of my Tek type D plugins, a high gain differential tube amp. It had a major imbalance in the front end. Turns out the original matched tubes were not installed. I took one no name tube out and found several others that matched the other (GE of the same type and construction), after putting one in, it was close enough to do a rough cal and made it useable. I did not go through the trouble of matching, electrically, a pair of them (it is still not balanced fully, maybe later). Most of the time I would say it does not matter, and you can just do the failed part. Again it depends on application and requirements.
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