I’ve got a red concert lead on my bench. I’ve come to the conclusion from testing that Q3 is bad (reading voltage from collector to emitter). This unit has 22-3155 7613 transistors (not available) instead of the still available 2n3055 listed on the scheme. Are these interchangeable? Considering the scheme should I replace all 5 Q’s with 2n3055 like the original scheme? Can I just replace one or need they be changed in pairs similar to tubes?
