Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Willisamps on June 15, 2019, 05:14:06 pm

Title: 1949 Gibson GA-50T
Post by: Willisamps on June 15, 2019, 05:14:06 pm

Hey folks, I am trying to repair a Gibson GA-50T. It makes a very low volume distorted sound when full volume. However, when plugged into a variac and set to 70 volts, It sounds kind of decent. Is it possible a bias that is too high would make it sound quieter? I think the inverse is true with Fender amps. Thanks

Title: Re: 1949 Gibson GA-50T
Post by: shooter on June 16, 2019, 09:42:42 am

Quote

Is it possible

the GA50 schematic shows self(cathode) biased.  If the R is still 150ohms and the cap is good and the Plate volts are right, the bias should be good.

always start with verified good DC voltage, then we can wonder about things  :icon_biggrin: