Thank you all for your responses and the leads you have given,??Responses to some of your questions and some more questions:?"Have you checked/measured whether they're actually faulty?"?Yes I have, in the picture I have provided on the bottom there are the ends of 3 transistor leads. This was one that fell off as I removed the card and by far the worst corroded, so despite the fact that the rest still work. I need to replace this one.?"?I would suspect that these transistors are pre-drivers for the power transistors and may not be super critical to get an exact replacement."?Would an NPN or PNP with the same HFE suffice, or do I need to know more? Forgive me but I am a complete idiot when it comes to this kind of circuit design and their tolerances.?"Did you get manuals with the printer?? If so it should have ALDs (schematics)."Unfortunately not, and nor can I find any online.?"The 3286 printers and 3277 terminals where infamous for intermittent problems"Excellent, glad I bought something that will provide the true IBM experience.?Thank you,?Al?