Broken BSIAB

[YouAre]

I had a bsiab that i had working perfectly outside of the box, then when i put it in the box, it worked fine except it got a really crappy undertone when i rolled back my guitar volume. When i opened it up to investigate, the bsiab worked no more, i tried putting in mpf102's inplace of all the j201's but it does not work when its on. Any ideas what else could be giving me problems? would you suggest getting a whole new batch of j201's to try it out?

[petemoore]

Bias voltage check, audio probe, debugging page...
 I start with a continuity check between circuit battery clip + and -. then check all grounds...
 You could check if ground is getting made somewhere it shouldn't.