It has been a long time since I have but the last time I worked on one I had the distinct feeling it was made at the height of the Vietnam War in some dirty sweat shop in Asia. ... probably hand assembled with slave labor children and maybe with their feet.
Very amateurish, poor construction, crappy chassis, dubious components and lousy coupling capacitors, that are oil filled and probably leaky now...
pretty much a super cheaply made amp... similar in basic topology as a Fender Reverb amp but I think with EL34s, no classic eyelet board and incredibly inexpensive parts. And did I say cheap yet?
I can't remember if they were cathode biased power tube or not though.
It's good you like it a lot and I've always been able to make them sound good enough but I'd never give anyone a warranty on a repair nor would I ever want to own one.