My 3-Pro has been serving me faithfully for over a year, and all of a sudden I'm getting only about half the volume it should be putting out. This amp was always a beast until last Friday at a gig, I couldn't get any stage volume. Enough made it through the mic apparently as the recording sounded fine from off stage. At this particular dive bar I usually had the problem of being too loud, that master volume knob is normally pretty sensitive when turning up. Tone sounded normal though. So anyways, I'm not super tech savvy, but my friend/band-mate is and we(he mostly) went through to try and diagnose the problem. First thing we made sure it's not the cab (410HLF). It worked just dandy with his Gallien Krueger 700RBII head. We sent the 3-Pro preamp into the GK and it sounded normal. But when running the GK preamp into the 3-Pro, the volume problem was there again, so we figure the problem is in the driver section. We tested the first test point in the 3-Pro poweramp schematic (R1), and it checked out. Second test point did not however, voltage was a bit high I believe. (Neither us of has money for a fancy function generator so we used a laptop with a program I can't remember the name. Think it did the job though.) So we thought maybe the problem is somewhere around the 12AX7 circuit. It was a pain in the arse but we pulled the whole poweramp section out and he checked for cold solder joints. Nothing stuck out. We put everything back together as it was getting late, but my friend's next guess was to check the BJT transistors. He can fix anything electronic, but isn't as familiar with this particular amp as an amp tech or bass junkie who sees them all the time. I told him TalkBass is always my goto. Anyone have any similar issues? Anyone have experience with those transistors in the driver section going bad, or know of what could have happened there? We didn't think it could be the mosfets. Also changed the tubes as I already had a new set of JJ's. They didn't make a difference. I'm sending my band-mate a link so he can register and chime in with anything I missed. If anyone has any suggestions I would be forever grateful. Hopefully my friend and I will be able to reconvene and solve this riddle. Thanks for reading.