Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: angelodp on February 29, 2020, 01:05:48 pm

Title: AB165 Bias upgrade
Post by: angelodp on February 29, 2020, 01:05:48 pm

Hi, do I understand Doug's article on Bias upgrade correctly to include the AB165. The AB 165 has a balance system and i want to put in a proper Blackface Bias.  I read that I need to install two 220k resistors and i see the correct position, in addition to other wiring changes and cap upgrade. My question is, do i need to remove the other two 220k's that are further down the line.

Title: Re: AB165 Bias upgrade
Post by: sluckey on February 29, 2020, 01:31:00 pm

Make it look exactly like this...

     https://el34world.com/charts/Schematics/files/Fender/Fender_bassman_aa864_layout.pdf