Marshall JMP experts I need your help!

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jharpersj

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Hey dudes! I have a chance to grab a JMP 50W, 4 input, has a few mods I know of where the channels are internally jumped. Serial ends with a J according to the store. But any of the experts would chime in if they see anything suspect in the pics I would greatly appreciate it! The amp sounds tremendous but I fear what I don't know LOL. No clue on the year, they said maybe 77 but that was when they had a master so not sure. Also for reference price is $1700

thank you everyone I so appreciate it! Have been wanted an old marshall for a long time
Jim
 

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For whatever it’s worth, send Dave Friedman an email. He’s a quick responder and he is happy to help with this kind of stuff in my experience.

He’s been inside more Marshall amps than probably most people on the planet 🤷‍♂️

Friedmanamps@gmail.com
 
Not sure how many Mustards might have originally been in it, but most have been replaced with those orange drops....but that's not necessarily a bad thing as I just recently grabbed a 69 'FrankenMarshall' that has kinda the same thing. It still sounds killer.
But, ask for a pic of the topside, as we can tell you if the transformers are original.
 
Lotta changed parts…those bias caps are way overkill voltage wise. Maybe all he could find. Orange drops are not original, but not bad. Probably just chnaged over to a 2203/4 preamp. If it sounds good and is cheap enough might as well.
 
Racerxrated said:
Not sure how many Mustards might have originally been in it, but most have been replaced with those orange drops....but that's not necessarily a bad thing as I just recently grabbed a 69 'FrankenMarshall' that has kinda the same thing. It still sounds killer.
But, ask for a pic of the topside, as we can tell you if the transformers are original.
Click to expand...
OK will do!
 
Greazygeo said:
Lotta changed parts…those bias caps are way overkill voltage wise. Maybe all he could find. Orange drops are not original, but not bad. Probably just chnaged over to a 2203/4 preamp. If it sounds good and is cheap enough might as well.
Click to expand...
thanks for the help price is $1700
 
Greazygeo said:
Lotta changed parts…those bias caps are way overkill voltage wise. Maybe all he could find. Orange drops are not original, but not bad. Probably just chnaged over to a 2203/4 preamp. If it sounds good and is cheap enough might as well.
Click to expand...
what impact does the bias cap have in this case? thanks
 
looks like a 2203/04 conversion of some sort .. how does it sound?
 
lespaul6 said:
looks like a 2203/04 conversion of some sort .. how does it sound?
Click to expand...
That makes sense, several people I trust said it was incredible, super ballsy and that it just ripped but they described it to have VH level of gain so I suspected some sort of mods, also the price seems to be adjusted for that, I am going to hear it on sunday, its an hour away but it is a reputable store with a 45 day return policy.
 
Not stock parts:
Mid trebble and volume pots
Most every resistor and cap on the board
Cathode follower resistor and input grid.
Input jacks
Preamp tube sockets
Added ground by power cable
Also looks to be converted to 2203 style input and preamp.

The bus wire looks a bit hokey.
As does the standby wire leads (looks a little thin to me).

As a mod candidate it would probably be a good buy. Or if your cool with knowing most of the components aren’t stock. Any pics of the transformers? If you could get a pic under the board that would be nice, it could be jacked up given how many parts have been changed.
 
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Chubbs said:
Not stock parts:
Mid trebble and volume pots
Most every resistor and cap on the board
Cathode follower resistor and input grid.
Input jacks
Added ground by power cable
Also looks to be converted to 2203 style input and preamp.

The bus wire looks a bit hokey.
As does the standby wire leads (looks a little thin to me).

As a mod candidate it would probably be a good buy. Or if your cool with knowing most of the components aren’t stock. Any pics of the transformers? If you could get a pic under the board that would be nice, it could be jacked up given how many parts have been changed.
Click to expand...
thank you, this is a great help! I will try and get those pics
 
If the store has a return policy, just get it. All the hummin’ and Har’n (wasn’t sure how to write that 😂) about what, who, why, when which could consume days can be resolved by 5 minutes of playing it…lol
Unless of course that return possibly includes, expensive shipping on your part, I could see the dilemma.
I got a ‘75 lead and bass a while ago now and it had replaced iron (MM) and God knows what is on the board, I still have never bothered taking a look. It was a reasonable price and because I got to play it when I saw it, just bought it. Nothing like being able to just hear the thing. I could only imagine how I would have fretted if I saw it online and was looking at pics of different iron and replaced parts.
 
It’s a 2204 conversion, 10k cold clipper. Looks to be modded to a stock 2204. There is A LOT that can be done with these if you are inclined to have it modded. The guys here are correct, it’s had a lot of components already replaced. I’d want to see the transformers before considering a buy.
 
I think you already have enough info by now but if you still want more you can always make a post in the vintage section of the Marshall Forum. There are some very knowledgeable guys there.
 
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