Converting the 230v transformer on marshall jcm2000-dsl for use on 120v u.s. Power?

[Mango Moon]

Greetings All!

I've got a 230V (UK) version of the above referenced amp and I'd like to convert it for use here in the US at 120V. I'm told that the transformer is probably dual primary or "universal" in nature and that the conversion process is rather simple, but I've seen additional references to jumpers and fuse ratings as well.

Can someone offer me any guidance on this subject?

For example, is the conversion process something that I'd be likely to handle myself without visiting a trained amp tech (i.e., buying another internal/replacement transformer)? Or will it require an external transformer of some sort? Are there likely to be any technical guidance materials (instructions) available out there anywhere? I'd greatly appreciate any help I can get.

Thank you!

[Jazz P Bass]

You may or may not have a transformer that can be changed over.
If you do, the separate primary coils get wired in series & the fuse current rating is doubled.
If in doubt about any of this statement, take it to a tech.

[Mango Moon]

Jazz,

You've said that I . . . "may or may not" have a changeable transformer . . . but isn't there a more definitive way to determine this before going any further? In other words, was the JCM2000-DSL50 product line shipped with different transformers over the years? And aren't there solid references available somewhere (either from Marshall or whomever) that would resolve this question?

Other threads that I've uncovered on this subject (here and elsewhere) would seem to imply that they were ALL 'universal' and that the conversion was simply a change in jumpers and fuse, but ideally, I'd like to get confirmation of this including some specific guidance on performing the actual steps, if possible.

Here is a quote from a recent thread here on MEF (http://music-electronics-forum.com/t24150/) that seems to be relevant:

"I have used my TSL 100 on tour in the US, Europe, and Australia. Pretty sure Marshall used the same PT on all 2000s, regardless of where they were to be sold. You just swap a few wires around to use the PT primaries in series instead of parallel. The stock PT will get you about 500V B+ with 120VAC on parallel windings or 240VAC on series windings. European 230VAC or 220VAC will give you a slightly lower B+, but the amp plays fine and it's really not noticeable. See the schematic to check which wires should be rearranged. They are the spade connectors on the mains input board with the fuses, which connect to the PT."

[exclamationmark]

You can pretty easily tell by looking at the PT. If it has 4 wires coming from the primary, you most likely have dual primaries, which allows voltage conversion. Skimming through the service schematics, it looks like there are connectors which you can shift around to connect the primaries in parallel/series. I wouldn't know anything about revisions as such, though.

[Mango Moon]

Unfortunately, I don't have the amp sitting here to physically inspect and I won't for perhaps a month or so. That's kinda why I was hoping (praying) for a clear answer about the entire DSL-50 product line as a whole, rather than individual DSL-50 amps. If broad-based information such as this isn't readily available, then I guess I'm stumped, but there's something I don't follow . . .

If Marshall issued different DSL-50s with differing power transformers as some seem to suggest (i.e., certain models of DSL-50 with universal PTs, others without), wouldn't they also have to issue different schematics and other technical records for each? As I said earlier, I'm not a trained amp tech, so I can't answer this question, but I've got a schematic here for the DSL-50 and I've only been able to locate ONE version of it (not multiple versions with differing models of PT).

[Enzo]

JCM2000 is a non-specific term. it refers to an entire series of amps. Even DSL is not specific. There is the DSL100, the DSL50, the DSL401, the DSL201, and those range from a single pair or EL84 output tubes to four 6L6s. SO a blanket statement like "Pretty sure Marshall used the same PT on all 2000s, regardless of where they were to be sold." can't be true without some additional qualification.

I'm told that the transformer is probably dual primary or "universal" in nature and that the conversion process is rather simple, but I've seen additional references to jumpers and fuse ratings as well.

Well, yeah. In the case of dual primary or "universal" transformers, the process is simple, but moving jumpers is the process by which the wiring change is done.

And yes, the fuse must change, because for the same power going through it, 120v uses twice the current that 240v does, so the fuse needs to be twice the current for 120v versions compared to 240v versions.


I have no idea if Marshall used the same on ALL the amps in this model. The only one we need concern over is the one you have, so the easy solution is this - what part number is on your power transformer? I think you have a real good chance of being correct, the schematic says for country codes A,B,C,D,E,H,K,M,S,T,U,V,X, use TXMA00067 (Part 96B-17 and only country code J uses TXMA00068. And if I had to guess, that J is for Japan and their 100v mains. SO I guess they use the same part in MOST, but not quite ALL of the DSL50s.

The DSL50 schematic has a page for the reverb circuit and the mains circuit, and on that page, the alternative wiring for the voltages is presented.

Just checking, the DSL100 does indeed use different power transformers

[Mango Moon]

JCM2000 is a non-specific term. It refers to an entire series of amps. Even DSL is not specific. There is the DSL100, the DSL50, the DSL401, the DSL201, and those range from a single pair or EL84 output tubes to four 6L6s. SO a blanket statement like "Pretty sure Marshall used the same PT on all 2000s, regardless of where they were to be sold." can't be true without some additional qualification.

Well, yeah. In the case of dual primary or "universal" transformers, the process is simple, but moving jumpers is the process by which the wiring change is done. PARALLEL vs. SERIES, GOT IT!

And yes, the fuse must change, because for the same power going through it, 120v uses twice the current that 240v does, so the fuse needs to be twice the current for 120v versions compared to 240v versions. 6A vs. 3A, GOT IT!

I have no idea if Marshall used the same on ALL the amps in this model. The only one we need concern over is the one you have, so the easy solution is this - what part number is on your power transformer? I think you have a real good chance of being correct, the schematic says for country codes A,B,C,D,E,H,K,M,S,T,U,V,X, use TXMA00067 (Part 96B-17 and only country code J uses TXMA00068. And if I had to guess, that J is for Japan and their 100v mains. SO I guess they use the same part in MOST, but not quite ALL of the DSL50s.

The DSL50 schematic has a page for the reverb circuit and the mains circuit, and on that page, the alternative wiring for the voltages is presented.

Just checking, the DSL100 does indeed use different power transformers

Thank you, Enzo. Very helpful as always!

I (for one) fully realize that the DSL50 is a different model from the other DSL's, and further, that a 100w amp would more than likely have different PTs from a 50w, etc. That part I follow! I'm focusing here specifically on the DSL-50 model (a UK version of the amp that is owned by my eldest son, but not currently in his possession), and whether (in practical terms) it is worth keeping. So, given what I'm learning here, I think the answer is yes. In other words, more than likely, the conversion is indeed "quite simple". And besides, if in-fact it did prove to be problematic (assuming he was willing), he'd easily be able to swap out the entire PT for superior (120v) Mercury iron if he wanted to upgrade, right?

[g1]

http://www.drtube.com/schematics/mar...63-02-iss3.pdf
From what the schematic shows, you would move the wire from terminal W5 to W6, move wire from W4 to W1, replace the mains fuse with a 3amp slow blow.

[R.G.]

And remember: when you start tinkering with AC power wires, you're playing a quick hand of "You Bet Your Life". Mother Nature may call your hand at any time in the future.