Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: firemedic on November 23, 2011, 11:39:09 am

Title: bias tap question
Post by: firemedic on November 23, 2011, 11:39:09 am

I got my first non-CT power tranny from Weber, the one for a TR. It has a 50vac bias tap but with no ground reference CT, where do the 2 bias leads go?

Specifically, I figure the blue lead must feed the bias supply like I'm used to, but what about the other lead?

Title: Re: bias tap question
Post by: ernie_jr on November 23, 2011, 11:45:24 am

The red/yellow is the CT for the high voltage and the bias, blue red is the bias tap. Wiring diagram is on Weber's
website.
Ernie

Title: Re: bias tap question
Post by: sluckey on November 23, 2011, 12:24:55 pm

Sounds like you have a PT with a totally separate bias winding (like the Reissue Twin Reverb). If so, one bias lead goes to ground and the other goes to the bias circuit. Refer to page 8 of this schematic for an example...

http://www.el34world.com/charts/Schematics/files/fender/65_twin_reverb_%20manual.pdf (http://www.el34world.com/charts/Schematics/files/fender/65_twin_reverb_%20manual.pdf)

Or see this pic...

Title: Re: bias tap question
Post by: firemedic on November 23, 2011, 05:34:28 pm

Thanks!

Title: Re: bias tap question
Post by: stratele52 on November 23, 2011, 05:59:06 pm

Quote from: sluckey on November 23, 2011, 12:24:55 pm

Sounds like you have a PT with a totally separate bias winding (like the Reissue Twin Reverb). If so, one bias lead goes to ground and the other goes to the bias circuit. Refer to page 8 of this schematic for an example...

http://www.el34world.com/charts/Schematics/files/fender/65_twin_reverb_%20manual.pdf (http://www.el34world.com/charts/Schematics/files/fender/65_twin_reverb_%20manual.pdf)

Or see this pic...

+1 slukey