As other Quad jammers will recall, my 1987 clone came over all poorly mid way through the afternoon, so we shut it down. Took it to our jam last Monday, got it out of the combo and powered it up. Sounded fine so I thought I'd check the bias, 84mA. SHIT.... turned the lights off but they el34 weren't redplating . So I adjusted it back down to 38mA and continued playing it. Was fine all night.
Now this has London Power powerscaling,, but other than this being faulty is there any other reason why the has would drift by such an amount?
Comments
If the bias has drifted on *both* valves, it probably points to the power scaling circuit as the culprit. If it's just on one, faulty valve or leaking coupling cap.
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein
Other than that, the bias voltage is entirely controlled by the bias tracking system and pot.