You are so right. Dried out electrolytic caps are also common in old guitar amps. I have an old buddy who likes to restore old guitar amps and does well trading vintage tubes. Apparently they aren't created equal. He will buy an unknown amp cheap And replace the coveted tubes with cheap ones and resell the tubes and "restored" amp for more than he paid.SalutNounou wrote:Another domain where you could make money repairing electronic devices would be in Vintage Hifi. ...Usually the repair work is just to change the old chemical capacitors, so it is not very difficult to do.
DIY audio is fun. I had the opposite experience in grad school. I wanted to build but I found it was cheaper to buy used stuff rich guys got tired of. Pre craigslist...rec.audio I think. I missed out on learning tubes.
I just thought of another one. 1980s motorcycle ignition systems. Some of the Japanese makes like Suzuki are no longer providing cdi units for their old bikes. It's a show stopper if you have a cherry bike with a burned cdi. A cottage industry exists where they obtain a good unit, read out the output under simulated input and then replicate the old analog circuit with microcode and a chip. Somebody I know did this for Mercedes tachometer amplifiers because the real ones are grossly overpriced.