Marshall DSL 50 making me very frustrated

[Randall]

I have a JCM 2000 DSL 50. It was dropping power levels. I gave it the full cleaning to rule out pots, switches, FX loop jacks, etc. Now I find the clean channel A "crunch" switch (SW1) does nothing, and the Gain pot (VR1) does nothing. and Relay 1 does not switch on. So I go about attempting to trace signal path, but find the two conductor cables on this amp to be very difficult to follow. CON2->Con3 JCM2-60-00, except when I find the other end of the cable it's not Con3 or whatever. Then I discover there are several different issue numbers for the boards, and you have to have the right version in front of you to follow all these cables. I found a schematic for the front panel board, I have a Issue3, but this issue 5 matches the cabling in the amp. But I cannot find a Issue 5 for the tube board, only issue 1, so I don't know how I am going to figure this out.

front panel bd JCM2-61-00 issue3 and JCM2-60-00 issue 5 is what I really need. Or, can anyone take a look at the issue 5 front panel drawing I did find and have any advice for why the relay is not switching on? It's in the upper left section. What a PIA!

http://www.lydian.ca/Marshall_DSL_fi...FrontBoard.pdf

[Jazz P Bass]

Try this.
It's from the DSL 100, issue 5 power board.

jcm2-60-02-iss5_TubeBoard100w.pdf

[Randall]

Thanks, but that's a 60-02, I have 60-00 issue 5.

[g1]

I think expecting the numbers on the drawings to match exactly the numbers on the board may be asking too much of what is now Marshall. Sorry.

[g1]

And further to that, I believe the schematic Jazz posted is the one you seek.

[AmpFix]

I think expecting the numbers on the drawings to match exactly the numbers on the board may be asking too much of what is now Marshall. Sorry.

They match. You need to have the correct schematic : Hw assembly number and issue number must correspond.

[AmpFix]

You mention a relay not switching. Are you 100% sure? If that's the case, its probably just one of the switching transistors MPSA13, but before you go there, the crunch/clean button on the green channel does not involve a relay.

Relays come into play only when switching from green to red channels.

Could you describe the problem(s) you're experiencing? Does the amp switch channels as it should? Volume drops could be caused by one of the LDRs going bad.

[Randall]

I'm not 100% sure about Relay 1 switching, but I am 100% sure that Relay 2 is switching, as I hear a very clear "clink" while listening with a stethoscope that I don't hear on Relay 1. That said, yes the amp is switching channels, everything works fine on the Lead channel, but on the green channel only the Volume pot works (VR2), the Gain pot (VR1) and the crunch/clean switch (SW1) have no effect.

[g1]

They match. You need to have the correct schematic : Hw assembly number and issue number must correspond.

Normally they should match. But in this case somebody screwed up. Drawings labelled JCM2-60-02 are for boards marked JCM2-60-00. Even the newest replacement boards are still marked JCM2-60-00.
There were never any boards with JCM2-60-02 labelled on the boards. I have to assume that the "-02" was a typo on the schematics.

Anyway, my point was that Randall not let this get in the way of fixing the amp. There is no schematic labelled to match the board labelling.

[AmpFix]

Normally they should match. But in this case somebody screwed up. Drawings labelled JCM2-60-02 are for boards marked JCM2-60-00. Even the newest replacement boards are still marked JCM2-60-00.
There were never any boards with JCM2-60-02 labelled on the boards. I have to assume that the "-02" was a typo on the schematics.

Anyway, my point was that Randall not let this get in the way of fixing the amp. There is no schematic labelled to match the board labelling.

Grabbing schematics from the 'net and saying they don't match your amp isn't really a valid point. And saying that you never saw a board labelled JCM2-60-02 doesn't prove anything. There are several variants that use the JCM2 prefix from DSL 50, DSL100 to TSL 60, TSL 100 and the special editions, plus the combos.... but you might be right. the -02 could be a typo. I doubt it though.

Regardless, the problem should be easy to fix. If a relay isn't switching back and forth, that's easy enough to diagnose but the fact that SW1 doesn't change anything is odd as no relays are involved there, regardless of board revision or issue number.

[g1]

Here is a picture of the newest issue (like issue 20 or something).
(https://www.tubesandmore.com/products/P-H219)
There were no boards labelled JCM2-60-02.
People have been fighting this Marshall typo for almost 20 years, it should have been put to rest long ago.

[AmpFix]

Here is a picture of the newest issue (like issue 20 or something).
(https://www.tubesandmore.com/products/P-H219)
There were no boards labelled JCM2-60-02.
People have been fighting this Marshall typo for almost 20 years, it should have been put to rest long ago.
[ATTACH=CONFIG]38800[/ATTACH]

I'm curious: Do you have the Issue 20 schematic? Does its schematic have the JCM2-60-02 naming?
Certainly weird.

[g1]

As far as I can tell, all schematics after issue 1 (or maybe iss.3) were labelled JCM2-60-02, even though the board never received the "-02" change.

[Jazz P Bass]

I don't see an issue with the connectors.
Preamp 3 goes to power amp 6
Preamp 6 goes to power amp 5.

The relays (1 & 2) are in series.
So if one 'clicks', so should the other.

If relay 1 does not energize then Sw1 & VR1 will do nothing.
(unless I am mistaken, the schematic shows VR1 as the 'switched' state)

Anyway, best to get the relay circuit working properly before worrying about connectors.
The schematic shows the relay circuit directly below the input circuit.

[Randall]

Indeed, but the issue I have with connectors is where is the drawing of the other end of the 6 pin Con4 in the relay coil circuit? It would help to know what is on those pins. However, since RL1 and RL2 coils are in series, and RL2 is clicking, but RL1 is not, we can assume RL1 coil is not open. LED 1 and 2 are switching back and forth, so that part is working. I am not going to be near my bench for a few days, but I am now inclined to replace RL1. Does this make sense?