I tinkered around with electronics in HS. I was a roadie for a music store, we provided sound equipment for small clubs and larger venues for bands like Spooky Tooth, Humble Pie, Genesis, King Crimson, ELP, more. Fun times.
I built several digital electronic gadgets, radios, Heathkit and Radio Shack things, am fairly competent with a soldering iron and circuit tracing.
Fast forward about 40 years and I got interested in bass guitar playing and came across a smoking deal on a broken Acoustic Control Corp 18” reflex bass amp (370 watt). Found schematics, spent a month of evenings in my office replacing components, then reconed the speaker, recovered the amp, eventually lost interest in guitar (no real talent for it), sold amp at a good profit. There’s a whole collector’s crowd for antique ACC amps and sound gear. Thing was almost 40 yrs old when I sold it.
This taught me a LOT about electronics I thought I knew decades earlier. Humbling. I basically knew nothing. But I did manage to get the thing working, even shipped it off to MadScienceWorks for calibration - I was off about ten ohms on one trim pot - which made me feel good. Buyer was happy.
What I did basically was replace every electrolytic capacitor, put a set of YUGE electrolytic caps in there (about 2 farad, like you’d use in a car boombox), all the little ones on the boards, replaced power transistors and used silver heat conducting paste, replaced most of the preamp components, tightening up the resistor tolerances to 1% instead of the traditional 5, and so on. Figured a lot of those components wouldn’t have aged well, electrolytic caps are notorious for breaking down if they’re not used often, random static charges can fry FETs and I probably spent $100 on components through mouser.com and digikey. The famous, traditional, amplifier buzz even went away.
If you know electronics, how to read resistors, have a schematic, VOM, oscilloscope, have at it. I’ve seen these boards, the schematics, and the only way I think I’d be comfortable reworking one is the same way I did the ACC 370 head. Change out anything that could be burned out, all the mosfets, SCRs, diodes (with higher reverse/peak voltages for a little extra insurance), and keep my fingers crossed I didn’t miss anything.
But time, said Herr Doktor Einstein, is money.
These days, I have other interests, hobbies, and I’m not half as hypomanic as I once was.
I still have my original (with loud relays), replaced the box with the newer ESS/S4 (?) box3 years ago and bought a spare on sale ($400) about 18 mos ago, just to have it. Just in case.
