Marshall Jcm 2000 DSL

[Captainrowd]

My 100 watt DSL head suddenly stopped making sound. I played one guitar through it, switched it to stand by, plugged a different guitar in and it made no sound at all. Now no guitars work in it. I know that its not a blown fuse or power tube, and it is not a bad cabinet or output jack. I've run other heads through the cabinet and tried other cables to connect the head to the cabinet, but no sound at all.

The unit turns on and can switch channels, but there is no "hiss" when I switch to the lead channel. . . there's actually no sound whatsoever. It seems that the amp is not turning off of standby. If anyone knows how to check preamp tubes or has heard this problem before, please help.

[Enzo]

Get out the voltmeter and start looking for missing high voltage.\

I'd expect to find 450-500VDC on the power tube plates and screens. An easy spot to measure that is the primary wires on the output transformer. The screen resistors are the rectangular cement ones on the main board - should be similar voltage on their legs.

[Amp Kat]

Check your cathode current sense 1 ohm resistors and plate resistors. How do you know it's not a power tube ? That's what usually causes all of the problems in these amps. What's weird about these amps is theres something not designed right in that power section as the first jcm2000 DSL I ever played just blew a 500ma fuse for no reason at all just sitting there doing nothing on standby and flipped the switch and nothing. You did check those (2) 500ma HV fuses right ? This amp was brand new and did it so I have to believe it is flawed plus all the problems we've seen on this board is like every other day with these amps.

[acorkos]

plug your guitar cable into the effects return jack and see if there's any sound. if so, your power tubes are likely ok, and your problem is in the preamp somewhere. i saw a dsl50 amp recently....V1 and V2 were cold, with a bad bridge rectifier BR62

[Captainrowd]

Thanks

I had to take it in. . . Time became more valuable than the peace of mind of fixing it myself. Apparently the tubes were not properly biased and one of the inner fuses was blown. Although the amp works fine now (with new tubes and pro bias, it sounds better than ever) please let me know if you think I got ripped off. . . cause i didn't know that there were more than two fuses in the thing.

[Twist]

Sounds like a common problem. How much did it cost to get repaired?

[Captainrowd]

cost

well it was $180 for the repair, the fuse, the new tubes, and the bias job. I would guess the tubes were between 60 and 90 dollars. This place in Escondido is just the bomb.