A good source for amp parts, and electronic parts for guitars:
I buy parts for old electronics, and old radio's that I fix up for people from this outfit and have been a customer for many years w/no problems.
Antique Electronic Supply... but don't let the company name fool you.
http://tubesandmore.com/
If you are looking for tubes for any amp, this is a good source.
I work on vintage Hammond B-3 Organs w/Leslie speakers, and the power amp is much like a guitar amp, using 6550 or KT88 tubes as finals.
You can find a wealth of misc parts for amps, speakers, and guitars here.
I had a woman ask me one time if I could fix her husbands old Fender "
apple flyer", as a surprise for him.
Had a hard time not guffawing in her face with that line. Yeah, I fixed it. Guitar stuff is easy to work on, but if a power transformer, or output transformer (tube amps) is cooked $$$ can get ugly.
Hope this helps someone.:beer;
Back in the early 60's (I was in my early 20's
) when the electric guitar garage rock band thing was just getting going, I worked an after-hours job at a music store. Kids would try to use any kind of amp or speaker from something like a church P.A. system, and would bring in speakers and amps that had litterally
been on fire from over use repaired. $100.00 transformers even that many years ago. LOL.