Calling the Marshall tweakers.

  • Thread starter Thread starter Jofipe
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Jofipe

Jofipe

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Can anyone see if this amp has been modded, or there is anything weird about it? It's a '83 2203 JMP.. probably one of the last produced for the Scandinavian marked, are these completely like all other prior 2203 JMP's?

I found these resisters under the red tape...

Anything else fishy about it, other than it has no engravings on the back.. also the JMP on the front panel is also missing

Cheerio

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I'm sorry about the size of the pics :((( Photobucket has gone nuts.. cant change it.
 
That does not look like any Marshall board I have seen... there should be the "Marshall" logo and "ST1" on that board... Maybe an aftermarket board but even the components dont seem right...
 
Right? And whats up with the fuse board? Maybe thats why the amp sounds so good haha...
 
The PCB looks factory to me. The hand lettering is the same, tho it is odd that it is missing the Marshall logo and ST1. The fuse board is probably the same one used in the Canadian amps, tho I have actually never seen a pic of one myself. Not sure what's going on with the resistor on there, and I see a burned spot!

That was very thoughtful of whoever modded it to include the original parts under the tape! Those parts connected between the Low input jack and Preamp Volume pot. I see a newer carbon film resistor there. It's a very common place to get more gain out of the circuit.

There is also a 10k R across the stock 10K cathode R, again increasing the gain.

Other than that, it looks original. How does the iron look?
 
Where can you see the burned spot? Thing is that the amp just farted and now only a small amount of audio comes out.. all the knob works, and I guess if it was the trannie, it would have smelled. I'm not very technically skilled myself, so I can't locate what's wrong. Any ideas? It happened after I had opened it up to take these pics... Fired it up, 2 secs of sound then silent - or very very low.

I guess the transformer looks good, anything I should take note of? Filter caps was recently changed.
 
Jofipe":1kbwztnl said:
Where can you see the burned spot? Thing is that the amp just farted and now only a small amount of audio comes out.. all the knob works, and I guess if it was the trannie, it would have smelled. I'm not very technically skilled myself, so I can't locate what's wrong. Any ideas? It happened after I had opened it up to take these pics... Fired it up, 2 secs of sound then silent - or very very low.

I guess the transformer looks good, anything I should take note of? Filter caps was recently changed.
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First try tubes.
 
glip22":31hg13og said:
Jofipe":31hg13og said:
Where can you see the burned spot? Thing is that the amp just farted and now only a small amount of audio comes out.. all the knob works, and I guess if it was the trannie, it would have smelled. I'm not very technically skilled myself, so I can't locate what's wrong. Any ideas? It happened after I had opened it up to take these pics... Fired it up, 2 secs of sound then silent - or very very low.

I guess the transformer looks good, anything I should take note of? Filter caps was recently changed.
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First try tubes.
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And another speaker cab.
 
Yeah, certain markets have different electrical codes or standards to follow which is why this one has the internally mounted fuses, much like the Canadian market Marshall's back then with their metal toggle switches and extra fuses inside. The only changes I noticed were same as someone else mentioned above.
 
Most of the oddities have already been pointed out.. def a gain mod in V1 with the piggy back 10k resistor. Maybe that's why you thought it sounded so good? All along you thought it was stock and someone went and upped the mojo..
 
Yeah, this amp is going back to where is came from, no doubt about it.

Thanks allot all!
 
yes mate a few tweaks here and there on that amp. Love the fuse board!
 
As another gentleman mentioned, this is a Marshall that was made for Canada and the boards are factory. The gain mod is one I came up with many years ago and posted on the Ampage and it was later reposted on Schematics Heaven. It's simple but effective for adding more gain, IE: installing a 10K across a 10K gives you 5K. My Mod specified a 4.7K but 5K is more than close enough for rock-n-roll (lol). The burned spots are most likely the heater fuses. This is easy to bypass and generally speaking these amps sound just as good as the JCM800's that did not have the fuse boards. I hope this helps and if anyone has any questions please feel free to ask/post them and I will do all I can to help.


Many thanks & have a great Friday morning! :)
Trace
 
Hey Jonas,

Like Trace said, only a small tweak on that amp and as for the fuse board.. That could always just be removed and bypassed if it's causing any problems. That's a great amp!

What filter caps were installed and when was it done? Those black caps look like the stock caps used on the early JCM800's. Either way, i have had plenty of failing filter caps, even new ones. Get it to a good tech and they can fix her up.
 
Thanks guys!! I went down and delivered it to the tech.. In some way I wasn't too keen on it anyway, so I told the guy i got it from, that i'll fix her up, but i'm not interested in the purchase. It was 1000€ also.. quite much for this amp I think. I'm on a lookout for another one :) I'm finding quite many in UK and EU.. on evilbay, but they are local shipping or pickup only.

Is there any special difference from the late 2203 '76 models to the newer post '80 models?
 
voodooamps":21jh6wcw said:
...The gain mod is one I came up with many years ago and posted on the Ampage and it was later reposted on Schematics Heaven...
Click to expand...

I'm sure you or I were not the first people to look at that 10k cathode R and find a glowing light bulb over our heads! ;)
 
voodooamps":3rczw6ik said:
As another gentleman mentioned, this is a Marshall that was made for Canada and the boards are factory. The gain mod is one I came up with many years ago and posted on the Ampage and it was later reposted on Schematics Heaven. It's simple but effective for adding more gain, IE: installing a 10K across a 10K gives you 5K. My Mod specified a 4.7K but 5K is more than close enough for rock-n-roll (lol). The burned spots are most likely the heater fuses. This is easy to bypass and generally speaking these amps sound just as good as the JCM800's that did not have the fuse boards. I hope this helps and if anyone has any questions please feel free to ask/post them and I will do all I can to help.


Many thanks & have a great Friday morning! :)
Trace
Click to expand...


Yes I do have a question.. what other simple mods were you fond of?! lol Your amps sound great.
 
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