Zaphod B
Raccoons-Be-Gone, Inc.
I decided to re-tube my Matamp GT 100 since one of the old tubes had become micophonic.
This amp uses 2 12Ax7 premap tubes and 4 EL34 finals. I ordered Sovtek 12AX7's (I was looking for an earlier breakup and this is what was recommended) and a matched quad of JJ EL34s. I ordered the tubes from Antique Electronic Supply and the salesguy seems knowledgeable.
Anyhow, old tubes out, new tubes in. I have no idea if this amp is supposed to require re-biasing with new tubes but the last time I did this with non-matched garden-variety Sylvania tubes the amp sounded great and ran fine.
Hooked up the speaker cab, plugged in the head, powered up and let it warm up. Plugged in the Les Paul and the amp was noticeably louder. The tubes took a good five minutes to warm properly and clean up. Everything sounded good.
I noticed that all 4 of the final tubes were lit up like a fucking barbeque grill. I don't recall this phenomenon from the last set, but I may not have ever really looked. The head was generating a lot of heat but it usually does.
I decided to let it idle for a while to see what would happen. I turned the preamp drive all the way down, as well as the bass boost and overall volume control. The final tubes were staying well lit up, and it kind of looked like a blast furnace back there.
It took 15 minutes for the pop. No smoke or fire. The finals were still lit equally but the amp was dead silent (none of the normal low-level hum) and produced no musical output. I uplugged it and let it cool, and checked the two fuses. The mains fuse was OK but the other 1-amp quick-blow fuse had blown.
I hope I haven't really fucked it up.
I plan on replacing the blown fuse and putting the old tubes back in to see if there is any life left. If it works as it did before, I will first try the new preamp tubes with the old power tubes, then the old preamp tubes with the new power tubes to see if I can isolate it a bit.
I think I'll be visiting Mr. Amp Repairman in any case.
Hold me.
This amp uses 2 12Ax7 premap tubes and 4 EL34 finals. I ordered Sovtek 12AX7's (I was looking for an earlier breakup and this is what was recommended) and a matched quad of JJ EL34s. I ordered the tubes from Antique Electronic Supply and the salesguy seems knowledgeable.
Anyhow, old tubes out, new tubes in. I have no idea if this amp is supposed to require re-biasing with new tubes but the last time I did this with non-matched garden-variety Sylvania tubes the amp sounded great and ran fine.
Hooked up the speaker cab, plugged in the head, powered up and let it warm up. Plugged in the Les Paul and the amp was noticeably louder. The tubes took a good five minutes to warm properly and clean up. Everything sounded good.
I noticed that all 4 of the final tubes were lit up like a fucking barbeque grill. I don't recall this phenomenon from the last set, but I may not have ever really looked. The head was generating a lot of heat but it usually does.
I decided to let it idle for a while to see what would happen. I turned the preamp drive all the way down, as well as the bass boost and overall volume control. The final tubes were staying well lit up, and it kind of looked like a blast furnace back there.
It took 15 minutes for the pop. No smoke or fire. The finals were still lit equally but the amp was dead silent (none of the normal low-level hum) and produced no musical output. I uplugged it and let it cool, and checked the two fuses. The mains fuse was OK but the other 1-amp quick-blow fuse had blown.
I hope I haven't really fucked it up.
I plan on replacing the blown fuse and putting the old tubes back in to see if there is any life left. If it works as it did before, I will first try the new preamp tubes with the old power tubes, then the old preamp tubes with the new power tubes to see if I can isolate it a bit.
I think I'll be visiting Mr. Amp Repairman in any case.
Hold me.