Another Marshall JCM2000 DSL on the bench

[selloutrr]

who wants to help!!?!

the amp is on it's way to the bench...
it was playing and sounding fine then the amp sort of just put it's self in standby. flipped standby and it came back on after a couple minutes.

this amp also has a pop when you power down.

before i make suggestions i'd like to hear if anyone else has any...

[selloutrr]

ok the preamp tubes test good the PI tube could be better balanced and the Output tubes are way out of matched.

I can't express enough my dislike for this model of marshall amplifier they are nothing but trouble and dissapointment. they truly are a text book example of why not to cut corners and make cheap amps on PCBs.

the pop is from an arching trace being cut to close together.

[Deric]

Is it a DSL401?

They use DC heaters on the preamp tubes. The rectifier on the board gets hot and starts to develop cracks around the solder joints. Amp works fine for 10-15 min then stops when the solder joints expand and the heaters on the preamp lose power.

I've fixed 4 or 5 all with the same problem.

Good luck.

[selloutrr]

it's just the 100 model but the problem sounds exactly like what you discribed. this model is solid state diode rec. is the 401 tube rec?

[benoit]

It doesn't sound like in this case it has anything to do with the transformers but everyone I know who has owned one of these (4 guys) has had to replace one or both transformers at some point. That's not so good, Al.

[Deric]

The 401 is SS rectified. The problem with the 401 is not the main rectifier but the FWB for the pre-amp heaters. Does the 100 have DC heaters for the pre-amp?

[selloutrr]

here are the schematics yes schematic (S)

[Deric]

Check BR1 on "power supply" schem.

[selloutrr]

ok thank you i will check it in the morning. suggestions on how to remedy the issue? if it's a solder issue, resoldering or flooding it with solder, wouldn't help.