| Author | Message | ||
     Barry Bonds |
My Musicman head uses 5 tubes, one driver and 4 outs... I installed 4 new JJ's in my amp 5 months ago and afterwards was getting a popping noise, usualy after turning it on 5 min or so. I found it to be one of the output tubes by thumping on tube while it was on high power. The other day I was sitting playing and again the popping noises came up and then i heard a low hum, the amp seemed to have died. I looked in the back after turning it off and the same tube had a bright red plate glow. I thought the amp was completly dead, put another tube in its place as it worked fine, no popping what so ever. My assumption would be the tube was not all there when it was new, but is this usual for a tube amp to find bad new tubes?...thanks | ||
| michael kaus |
Tha MM's are hard on tubes. They have 700v on the plates and if it was bias a little on the hot side, they will eat up tubes. You probably had ONE bad tube-it happens sometimes especially in todays world of crappy tubes. Even JJ's are prone to a bad one every once in a while. I would suggest though that you have the idle current checked to make sure you don't have it cranked to high. It's not uncommon to find a MM amp that has been "biased" by someone more familiar with fender and marshall amps and has cranked up the idle current because "that's about where I set my Marshall". In other words, they don't know what the hell they are doing. 25mA of idle current on a 700v MM is MAX. I would suggest 23mA. Mike. (Message edited by admin on December 30, 2005) |