I kind of doubt is the transformer. Since the amp is pretty old, my guess is the power supply is failing. The capacitors may be drying out and retain much charge anymore. If you replace the caps, I would also consider replacing the rectifiers. The other problem could be the you have bad soldering joints which may be oxidizing (sp?) due to the age of the amp. Good Luck, Richard
Bad Transformer?
Hi, Last night as I was listening to my old dynaco St-70 (circa 1963), the amp went dark (all tubes went dark) for about a minute, it then revived and played for another hour perfectly before I turned it off. It wasn't the power supply to the unit as my preamp and cd player are also plugged in at the same place. I was wondering if this unit has a "cut out" switch when it begins to overheat. I have it hooked to my Vandy 2ce' which are pretty demanding. But then again, it just lit right back up after a minute so I don't know what was up. Any ideas?