1961 Zenith Stereo Amp Problem

[davet753]

The schematic I have is a Photofact, and it says line voltage was maintained at 117 volts for the readings. Zenith rates the chassis at 110 to 120 volts. Thankfully, a generous videokarma member has offered to scan and email me a copy of the factory service manual It'll be interesting to see what Zenith has to say.

I turned it on this afternoon and let her play for a couple hours. I noticed that after it had been on that long, the volume could be turned up much higher before distortion sets in than it does after only being turned on a shorter amount of time. To be honest, it just sounded better in every aspect after being on for a few hours. I know weak output tubes can sometimes perform better after being ran for a while, and weak output tubes could also be the reason for the bias being a little off. I guess it would also likely have an effect on adjusting the current balance pots for the grids, also.