Hi all,

I've lately been having trouble biasing my Torii Jr. (Mk 1). I had a set of tubes in it that, for whatever reason, I couldn't bias low enough. That is, I turned the screw in the bias pot all the way to the left, but couldn't get the meter to read .825 mv. They had been working fine, but were a little long in the tooth, so I assumed they were due a replacement.

So I replaced the tubes with a new matched quad of the Telefunken Black Diamond EL34s, and now I can't get the amp to bias high enough--I've turned the screw all the way to the right, and it won't read any higher than around .600. What might be going on? And how do I fix it? Appreciate any advice.