I have several questions, as this build was quite a bit different than richie's layout and has dual external bias pots. There are no layout or schematic diagrams with dual bias and this is causing me some confusion.
I have changed everything to richie's layout except what I think is dual bias related and when I turn on the amp and turn off standby it screams a horrible tone and there is a blue glow in v4 (EL34). I turn it off immediately. It worked OK before my changes.
First, the heater wires from v2 to v3 switch polarity (4+5 on v2 connect to 9 on v3 and vice versa), is this a problem?
John
Restoring a clone to richie's layout
Moderators: pompeiisneaks, Colossal
Re: Restoring a clone to richie's layout
Sounds like your negative feedback is coming back in phase. Swap the 2 OT primary wires (Ususlly red and brown) on the plates of the El34s and that will probably cure the problem.
Re: Restoring a clone to richie's layout
Thanks Dana, that solved that problem! I've never heard of that in all my perusing of this forum and the Plexi Palace and MetroAmp forums. I removed all the dual bias stuff since I couldn't quite understand it or get the current down low enough. The tone now is very good, much better than when I got it, but the sustain is crackly and almost like there is a gate on it. No hum or hiss though.
John
John
Re: Restoring a clone to richie's layout
It appears that a just purchased NOS Tungsram was causing the crackling, so that's taken care of, but it still has no sustain, it's like there is a strong gate on. Is this "blocking"?
John
John