What model Marshall Do I Have?

[888guitars]

I need a Schematic for my amp and I'm not sure what model I have. This is a 1980 JMP super lead 100.
Is it a 2203 or 1959??? The 4 inputs throw me off. It sounds more like a Plexi than a JCM800. I thought that the later JMP's were pretty much a 800. Not this one!?

[jamesmafyew]

It's a 1959. If there's no master volume, it's definitely not a 2203. Remember that there were even 1959s labeled "JCM800." The 2203 has one preamp volume and one master volume, since the first two gain stages are in series. The 1959 has the two parallel channels with two pre volumes.

[big_teee]

Here's a link to a user manual that shows the different models.
http://www.drtube.com/schematics/mar...-ld-manual.pdf
T

[888guitars]

Ok so when I look at the schematic, the 1959 has been made for a long while. How do I know which one is for my amp?

[jamesmafyew]

Since you know it was made in 1980 (the last year that the 1959 had a JMP designation before the JCM800 label was introduced), find the latest schematic you can. Even if you got the "correct" one, you might still find differences between your amp and the print. I tend to just find the most LEGIBLE schematic I can get, and then mark it up.

The site big_teee linked to has lots of Marshall schematics, check that out.

[888guitars]

Allrighty then I will start digging

[dumbassbob]

Thats a nice amp don't Mod it If you want to find you more go to the MetroAmp - Plexi style amp kits, amp forum discussion, and tech wiki. forum it is all marshalls and the guys are cool....Its is so good even big name techs go there

[Jazz P Bass]

Marshall 1959 SLP1

I think that may be called '1959 SLP1'
Here is the Wiki on it.
Link: Marshall 1959 - Wikipedia, the free encyclopedia
I have attached the schematic that I have.
It is a sweet amp.

[888guitars]

I am going to make sure it is in stock form. I see a dual pot for the presence?? I dont think that is stock. I want to fix that. also the bright channel is SUPER BRIGHT! may want to figure a way to tame that. This is maybe the loudest amp I have owned, I will be looking for some type of attenuator?

[big_teee]

I am going to make sure it is in stock form. I see a dual pot for the presence?? I dont think that is stock. I want to fix that. also the bright channel is SUPER BRIGHT! may want to figure a way to tame that. This is maybe the loudest amp I have owned, I will be looking for some type of attenuator?

You may not want to change that.
That sounds like a LarMar PPIMV master volume mod, and it allows you to play it at a lower level.
I have that in my 2204 and love it.
T

[jamesmafyew]

^ That would maybe explain why the words "Bass" and "Presence" have been scrubbed off the front panel.

[888guitars]

Ok so if it is the ppimv mod how would I check/test it? And what would that mean to my bass knob? Why not have that mod on the back or use one of the 4 inputs?

[jamesmafyew]

If it's a PPIMV, it will be inserted in the drive lines between the two phase inverter coupling caps and pin 5 of the power tubes. The pot wipers will go to pin 5s on each side of the push/pull. It's sort of taboo to alter the appearance of classic amps, so in this case it may have been done to retain more of the amp's value, keep the original cosmetics. Looks like less of a hack job, I guess?

[888guitars]

It has a 50/100watt switch on the back. Will this affect a PPIMV ?

[jamesmafyew]

Probably not. Most half-power switches either lift two cathodes or switch to triode mode. Neither would affect the PPIMV.