JCM800 2204 Gut Shot Questions

carrjimi

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Was going to buy this amp. It doesn't seem to look stock based on some of the gut shots I've seen online. Any ideas on what was done here? Thanks all!
 

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AtomicRob

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It's a little hard to see in that pic, maybe if you can get a clearer pic of the board. Appears to be some resistors that were replaced from the top (soldered on to the old leads) and a couple piggybacked resistors, and those orange drops wouldn't be stock either. But I can't quite tell what the values are, could just be repairs, or changing the bias range (does it have EL34 or 6550 tubes?)
 

carrjimi

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It is el34. when I went to pick it up today it was broken kept cutting in and out. I was wondering if I should go back and buy it and have it repaired?
 

Chris-in-LA

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Guessing that it was modded in 1992, definitely has some additional resistors and one added orange drop cap. Here’s a pic of mine for comparison from 1986, I believe that this one was stock when I got it. It’s running EL34’s.

1649826687294.jpeg
 

XTRXTR

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There is a big difference between stock as mfr'd and stock values.

My 20th Anni is stock St1 board but has the filter caps changed a few times.

It's been sitting in storage now for about 18 years when I stopped gigging with it and built my own.

The coupling caps may need to be replaced if I started using it again. 40 year old coupling caps, probably leaking DC now. I would have to test it first, obviously. I would buy filter caps and replace again just in case. I would put it on my Variac and slowly rise the voltage first, monitor the ripple before tubes get put in etc.
 

jgab

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You probably have a crappy solder joint that is cutting some part of the circuit in and out. It is tough to see clearly, but I counted 12 topside solder attempts on that board. When you solder from the top, it could cause a crusty/weak/cold solder joint underneath on the solder pad where the component needs to make connection. Obviously these boards aren't made to be worked on from the topside. You could create an issue on the underside and wouldn't even realize it until you have problems and investigate the underside.

Difficult to say how hard it would be to fix. I would for sure separate the board from the chassis and check the underside.

If you don't know how to work on these amps then take it to a qualified tech.

I would love to fix it for you. Funny the person who worked on the amp looks like they signed the inside of the chassis. They should be embarrassed.

Oh BTW, finding exact replacements for those 0.022uf coupling caps is very difficult, but there of plenty of very similar replacements that would be better suited than those two Orange Drops. They look gross in there.
 
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Spanngitter

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Try to source some green Ero/Roederstein MKT 1822, they fit perfectly.
if it would be my amp,and since you have to get in anyway, I would replace all coupling caps with MKT, in my ears they sound perfect in old Marshall’s…
 

jgab

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If you take Spanngitter’s advice and replace all your 0.022 caps with MTK 1822, I will gladly buy those crappy old caps you pull out of there.
 

carrjimi

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Let me ask this....

The cosmetics of the cab and chassis are in very good condition. They look pretty much perfect for a 30+ year old amp. Provided I can get it somewhere close to stock with what is available parts wise, would it be a good buy?
 

XTRXTR

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IMO the 2204 is the most versatile amp Marshall ever made. If the plan is to use this amp into the long future IMO it doesn't really matter that it is MFR stock or has after market stock values. Its a good buy IMO.
 

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