I recently bought a used Ampeg SVT 2 Pro and was hoping to get some tips on biasing it. It was working fine when i bought it, and still seems to be working fine, but the bias #2 light is very inconsistent. When i brought it home, my roommate opened it up and had a look at the tubes to and took one out to examine it better. After everything checked out ok, we plugged it in and biased it, and it seemed to be back to normal. But now when i turn it on after a day or so of not playing through it, the bias 2 light seems to always be a little different than it was the day before. The green light comes on before the red light when i adjust it, and stays where i put it while i play. But i powered her up today and there were no lights on in the bias 2 section. I let the amp warm up, adjusted the bias 2 controls, and everything seemed fine. I was just wondering if i should have it looked at or if anybody had any suggestions as to how to fix this problem (if it is in fact a problem and I'm not just being paranoid). Please help
SVT 2 Pro bias help... 
