JKMV12
Well-known member
Well i picked up the amp from the tech last Friday after he installed a new Mercury Magnetics O50JM-MM OT (the original OT shorted internally). So i bring it home and plug it in. Rebiased to 32mA (EL34's). I start playing the Super Clean and it sounds OK. I switch to the 1087 and find that the gain is severely compromised...which i have come to expect from that module...i think that one of the tube sockets is bad. If i readjust a tube slightly then it usually is fixed.
Though the real trouble starts when i switch back to the Super Clean and push the gain a little higher. I had Master at 50%, Gain at 50%, and Module Level at ~40%. I start playing and within seconds i see two white spots of light reflecting off the back of my guitar case behind the amp. Before i have time to turn off the amp it shuts off completely. I check the fuses and the power tubes fuses as well as the mains fuse are blown. Upon further investigation inside the amp i found that there is a big black spot around where one of the terminals from the OT primary connect to the board. The plastic terminal head is also black with some splatter on the metal plate behind it. So ya the power tubes arced internally and caused some collateral damage. Nothing else on the board was fried so that is good. I didn't see the underside of the board but hopefully that is fine too. I am mainly concerned about the OT. I just spent $182 on it.
It is with the tech again and i should have more info tomorrow...especially about the OT. He believes that the old OT screwed up the power tubes. Now i am going to stick with either 6550's or 6L6's. I might even try some KT88's. I just hope that the OT is fine and that it won't be too expensive to fix. I am also just glad it isn't worse.
Though the real trouble starts when i switch back to the Super Clean and push the gain a little higher. I had Master at 50%, Gain at 50%, and Module Level at ~40%. I start playing and within seconds i see two white spots of light reflecting off the back of my guitar case behind the amp. Before i have time to turn off the amp it shuts off completely. I check the fuses and the power tubes fuses as well as the mains fuse are blown. Upon further investigation inside the amp i found that there is a big black spot around where one of the terminals from the OT primary connect to the board. The plastic terminal head is also black with some splatter on the metal plate behind it. So ya the power tubes arced internally and caused some collateral damage. Nothing else on the board was fried so that is good. I didn't see the underside of the board but hopefully that is fine too. I am mainly concerned about the OT. I just spent $182 on it.
It is with the tech again and i should have more info tomorrow...especially about the OT. He believes that the old OT screwed up the power tubes. Now i am going to stick with either 6550's or 6L6's. I might even try some KT88's. I just hope that the OT is fine and that it won't be too expensive to fix. I am also just glad it isn't worse.
