one marshall amp fixed . problem ? crap factory workmanship

[geraint evans]

Ive sorted the problem with my it was due to a really bad solder joint on one of the capacitors
there was so little soldier on it i could pull it out with ease with my bare hands
marshall really are getting sloppy , i recently replaced all the plastic knobs but the new one marshall sent where rubish , the gold tip on each knob wasn't even glued on properly and just fell off !!!
but everythings sorted now and its working well

[melvin]

I just worked on a JCM 2000 that had a screen resistor mounted to the board in such a way as to short one of it's leads to the filament supply. Workmanship, design. Something's shoddy.

[andyjazz]

I have a JCM 2000 on my bench right now that started on fire! The foam under the CB which contains all the PT connections basically melted all over the place. What I have come to determine is that a lug on the PT (An unused one apparently) shorted against the mounting bolt (Which is about 3/16's away - all this sits under the board with all the PT connections) I'm thinking maybe moisture caused it to short, or something, I dunno but it's all black and burnt and the main CB is blackened on that side. I haven't pulled it completely apart yet.......any thoughts?

[melvin]

If you search here for JCM 2000 you will find these amps to be a source of infinite variety in problems. So how many ways can a JCM 2000 blow up? The world may never know...

[Billy R aka DynaFreak]

I just finished working on one where 220k resistors were installed where the 5.6k grid stoppers on the power tubes were supposed to be! My pet peeve with these is the little 1/4W plate resistors. I fixed one recently that had made the rounds of some other local techs and finally came to me. Exactly one plate resistor on the phase inverter had failed open. The one thing I do like about these amps is the modular construction that lets you pull a PCB pretty easily. Of course on a really well made amp you wouldn't need to be pulling PCBs all the time...

[Steve Conner]

So how many ways can a JCM 2000 blow up? The world may never know...

That's what the "2000" is, the number of different ways it can screw up.

[micri5446]

did you know some new marshalls are being made in VIETNAM!!!! a jungle....wow....which is worse?....an amp made in a rice paddie or a jungle.....how can you expect quality workmanship when you stuff is being made a few thousand miles away??

peace..............mike

[geraint evans]

arrrrrrrrrrrrrggg
problem still not solved !

i used the amp at a recent gig but the output volume has dropped drastickly , it was lucky the amp was miked up and was run through a 5k p.a rig but i had to rely on onstage monitering just to hear my self

does anyone what may cause a lost of output volume like this ?

Ger

[drewl]

What output jack are you using?
I think the 16ohm jack is the ground for the other two, so if that jack goes bad (usually melts from current pull) the other jacks don't work.
Of course it could the loop jacks, check those.
The 220k grid resistor thing was found and here's a good site with a few of the problesm, including the bias drift problem.

The Marshall TSL122 JCM2000 Repair/Mods Page

[Alex R]

Yeah the output signal goes across the closed 16 ohm output jack contacts when you're plugged into 8 ohms. It's pretty meaty and you can get arcing. Cleaning up those contacts might do it, otherwise it's a new jack.

[Ted]

A while back I fixed a 90s Marshall where the pcb-mounted rectifier for the DC heaters had never been soldered in. It had just sat there working away until one day it didn't .

One of those faults where you have to look twice to convince yourself you are really seeing what you are seeing.

[The Dude]

Sadly, these sorts of problems are not exclusive to Marshall.