can someone here fix some electronic boxes?

[supton]

I Googled " MJE520 transistor equivalent" and this came up;

The complementary PNP transistor to the MJE520 is the MJE370.

Not sure if you have an electronics background but in this case "complimentary" means "polar opposite--but in a matching way". Completely non-interchangeable. In this case "complimentary" would be like a nut and a bolt. They work great together but there is no way you can swap one for the other. When you need a bolt a nut won't do. [Ok you can get some threaded rod and stud it, but that's the analogy breaking down--in this case, there isn't a way to swap.]

 

[Papa Bear]

I'm a retired electronics tech and it doesn't look easy to me .... looks like a time-consuming PITA

 

[wdn]

I Googled " MJE520 transistor equivalent" and this came up;

The complementary PNP transistor to the MJE520 is the MJE370.

MJE520 is an NPN transistor. When you say "The complementary PNP transistor to the MJE520 is the MJE370." I'm not sure it means what you think it means. Complementary does not mean equivalent, which is what you said in your Goolgle search, and a MJE370 is not a suitable replacement for a MJE370.

NPN and PNP transistors are opposites not equivalents. Complementary, when discussing transistors, means that there is a PNP transistor that has similar characteristics to a NPN, such that they can be paired in a push-pull configuration. A PNP can never be substituted for an NPN in the same circuit.