Nintendo89

Just bought a JMP 2203 79-81
Ive been dreaming about one of those for years, but with my tele thinline
its REAALLY bright, Ive heard about clipping the bright cap everywhere,
Could have gotten the amp with this mod, but was whimpy enough to
choose all stock.
Cant someone please help me out just to locate the right wires to cut, with an image or drawing.
and I will look into it, And please dont warn me about the risks, I will get assistance, Right now I just need to locate it.
Really want this fixed asap, or else I will have to use another guitar atm.

Mike M.

Hi Nintendo89,

I posted the same question about a week ago. You can look at the post a few down from yours. PaoloJM provided great information in his reply. The link I've posted below also has a good picture of where the cap is and what it looks like. You'll have to scroll down a bit to see the part on the Brite cap. I have a reissue JCM800 2203, not an older one like yours. I'm assuming it's the same chassis but I could be wrong. I've never owned one prior to this. Good luck and let me know how it turns out. I haven't done it to mine yet.

Tales From The Tone Lounge; The Ultimate JCM800?

Nintendo89

Hi!

I found a guy who was willing to help me over the phone.
I located the cap as a blue square with two legs connected to
the master pot.
I just clipped the legs a threw the shit away
I will never need that much treble.
Im really pleased with the result,is still a bit bright with my Tele Thinline
but that guitar is insane on the other hand.
It sounded fucking great with my Les Paul equipped with superdistortion
PUs.
The treble level sounds really standard marshall now, its just that treble is my
biggest enemy in this game so I will probable use my TS9 pretty much.

Nintendo89

Theres just one think ive been thinking about, everytime you read about the bright cap,
people say its located on the PREAMP pot, Mine was on the MASTER pot, why is this?

PaoloJM

Not sure that I can help you there. The schematic for the JMP 2203 shows the bright cap on the pre amp volume just like with the JCM 2203.
I'm guessing it would work in pretty much the same way (though you'd need a higher voltage rated cap) but it is certainly not "stock". Has the amp ever been modified that you know of?

__________________
www.youtube.com/paolojm

Nintendo89

Hm thats weird, Is it supposed to look as I described?
A blue "Square" with 2 legs?

Where do you find these scematics?

No not modded at all what I have heard, except for that this cap has been removed before but put back before I bought it.
Would it make any difference that mines a late one (the one with S/N and Bigger logo)

PaoloJM

Nope, the one on the pre amp volume is a round brown ceramic disc with two legs.
The one you described sounds more like a polyester film cap which has a higher voltage rating than ceramics, this would be required to put it on the Master Volume instead as a ceramic here would soon "burst" it's dielectric.

I have found that Schematic Heaven - FREE Amp Schematics Tube Amp Schematics Valve Amp Schematics Effect Schematics Effect Pedal Schematics Guitar Amp Schematics Bass Amp Schematics Fender Amp Schematics Marshall Amp Schematics Gibson Amp Schematics Vox Amp Schematics is excellent for schematic drawings. DrTube is also a good site, just click on Guitar Amps link for different amps or you can go straight to the Marshall section.

My guess is that the original ceramic cap was removed from the preamp. The guy seems to have asked a tech to replace it for him to restore the amps value and the tech seems to have put in a bright cap on the MV instead?!?
Have a look at the wiper and left lug (as you look at it from the front panel) on the pre amp volume for evidence of the removal of the original cap. You may notice rougher looking solder joint depending on how cleanly the original cap was removed.

__________________
www.youtube.com/paolojm

Nintendo89

hm, that sounds worrying.
I will try to get a picture to show you