Ampeg V-4 arcing?

[g1]

That bias voltage seems low, especially without tubes. Have any of the resistors been changed, or is there a bias pot installed?

[themusic]

That bias voltage seems low, especially without tubes. Have any of the resistors been changed, or is there a bias pot installed?

I noticed on the flip side at R49 another 75k resistor was added I pulled it and now I'm reading -59v.
I don't see a bias pot. Now that I'm looking closely I think somebody tried to do a master
volume mod. R21 is missing and a jumper goes between R21 and the wire that runs to a pot out the back?
I going to try to clean this up back to original...before I go any further.
After unsoldering the wire coming from the r21 junction at least the wild bias has seemed to settle down
and I'm not getting the wild fluctuations thanks "I need a bigger Magnifying Glass"

[g1]

Seeing as it's already there, you really want a master vol. in these amps . Even the standard version like they did in he later models will be immensely useful.