Grid bias question for blues junior III

[Heisenberg]

Hey guys. I want to install an actual bias adjustment on my Blues Junior. I am assuming Remove R51 and R52, replace with a 50K trimmer - wiper to C- and the outside terminals to ~20v and ground?

If someone can tell me another way to do this, or if I am correct in my assumption, I would greatly appreciate it. Thanks!

[M Fowler]

Here is Doug Hoffman's new conversion board layout, his schematic only shows stock circuit so I did not attach that but you can visit Hoffman Amps Forum to get other details.

[sluckey]

I would replace R51 with a 50K pot and replace R52 with a 12K resistor. The 12K prevents dialing the bias voltage down to zero and ruining your tubes.

[Heisenberg]

^^^ Thanks. Worked great.