Any old amp should be checked for snubbers. If there is no snubber circuit for the bridge rectifiers then they should be replaced with soft recovery rectifiers. Beyond that, finding repair parts can be difficult to pretty much if not impossible. Through hole semiconductors are going obsolete at a pretty fast pace. I am horsing a few for many of my old amps.
Big vintage amps worth paying for and keeping for a long time
Lamm hybrids, Rowland 8t, Levinson 23.5 etc. How reliable are they and how expensive to fix if something goes wrong ? Capacitors, resistors needing replacement, after 25 years, 30 years, something else ?
I didn't mention Gryphon and Nagra, as examples, they are too expensive even old.
I didn't mention Gryphon and Nagra, as examples, they are too expensive even old.