I am also of '55 vintage. Studied electronics, and did radio in Michigan. Got bit by the music bug, and bounced around for decades doing day jobs and working a guitar by night.
Started tinkering / reworking tube hi-fi amps (Eico, Dynaco, etc) into guitar amps in my mid-teens.
I rarely do any commercial repair work any more. Last time was when an insurance appraiser brought me an AMS RMX16 in pieces. They had covered a claim and were looking to recoup whatever they could from the unit. They'd given the unit to a repair facility in California. But a year went by and it never got fixed, so they demanded its return. A so-called "technician" had completely disassembled the unit, pulled every card out of it (there are a lot of them), and then shipped it loose (with no packing) rattling around the inside of the chassis stuffed into a single-layer cardboard box, from California to New York, shipped economy. It was sickening, a total loss.
I build for myself, and occasionally repair things for friends. If they bring me something PCB, I'll open it up and look. If it's a monstrosity, I'm not bashful about sending it back like I got it (unfixed). Life is too short for futile endeavors (aside from doing music, naturally).