#1
Hey all, I have a 2002 Marshall JCM2000 DSL401. I know the pre-2003 models are prone to overheating, however I doubt that's what happened here. I've installed a 12v computer fan in the chassis, blowing onto the tubes to help reduce heat, and it definitely helped as the amp is infamous for it's scalding front plate, which the fan got rid of.

Basically, it was working fine maybe 3 or 4 days ago. I moved it a few days ago, no bumps or anything, brought it into a different room, then back to it's regular spot. The amp powers on- power LED active, I can hear the transformer buzzing, but both power and pre amp tubes (yes, all 7 visible tubes; ignoring the covered pre amp tube) are not lighting, and I'm not getting any sound whatsoever. I checked the mains & HT fuses, both tested good with a multimeter.

I replaced the power tubes about a month and a half ago, maybe a little longer. I biased them to within Marshall's recommended voltages. Pre amp tubes are original as far as I know, I bought the amp used, but in excellent condition, guy said it had never been serviced, but he hardly used it as he didn't play much guitar or something.

If I remember correctly, there might be a fuse on the board itself, but I really am not in the mood to pull the amp apart at the moment. Anyone got a clue what it could be?

I only have spares for the mains fuse, and the original (but still functioning) EL84s, no spare HT fuse though, and if there is a fuse on the board, no idea what it is. I guess I'll be finding out soon though. Any ideas? Thanks.
#2
I don't really know anything about the amp but it is probably a fuse. According to the schematic (dated 1997, revised 2002) there's a fuse labeled F4 that is for the filaments.

The schematic is here (scroll down to DSL401)
http://www.drtube.com/library/schematics/69-marshall-schemas#JCM2000-DSL

It could also be a bad solder joint in the heater circuit. Hope this helps...
#3
Quote by Invader Jim
I don't really know anything about the amp but it is probably a fuse. According to the schematic (dated 1997, revised 2002) there's a fuse labeled F4 that is for the filaments.

The schematic is here (scroll down to DSL401)
http://www.drtube.com/library/schematics/69-marshall-schemas#JCM2000-DSL

It could also be a bad solder joint in the heater circuit. Hope this helps...


Well, just opened it up, F4 tests fine as well. I haven't removed the PCB from the chassis yet though, preparing myself for that headache.
#4
guitar42697

this may seem trivial, but did you TEST (i know you said you did) it or just look at it? i have seen fuses that look good but test bad, and even vice versa.

just a wild shot.
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#5
Quote by trashedlostfdup
guitar42697

this may seem trivial, but did you TEST (i know you said you did) it or just look at it? i have seen fuses that look good but test bad, and even vice versa.

just a wild shot.


Quote by guitar42697
I checked the mains & HT fuses, both tested good with a multimeter.