Previously, I posted this thread dealing with a problem I was having with my ABM 500. To solve the problem, I replaced the preamp tube (EH 12ax7) with a Groove Tubes 12ax7. The problem remained. I found it odd, however, that the EH tube didn't look like it was the cause (it didn't have that milky look to it.) Upon further inspection of the circuitry, I noticed a 250mA fuse behind the 12ax7 that was definitley blown. So I went to the local electronics store, bought some fuses, and replaced the blown one. The problem, however, still exists. Any ideas?