1976 - Marshall 2203 - JMP - Restoration

Spanngitter

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For JTM/JMP which originally sported Mustards the only current production replacement I would install as coupling caps are Vishay/Roederstein MKT1813.
I have tried and compared a lot (Mallory, Solen Fast, SoZo, CDs, TAD Mustards) and for me only the MKT1813 do retain the sound as close as possible to Mustards.
For later (PCB) Amps you can use MKT1822 or WIMA with WIMA sounding a bit more modern, HiFi-esque and edgier on crunch so if you want to trim e.g. a 2204 more brown use 1822, however YMMV....
 

Chris-in-LA

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For JTM/JMP which originally sported Mustards the only current production replacement I would install as coupling caps are Vishay/Roederstein MKT1813.
I have tried and compared a lot (Mallory, Solen Fast, SoZo, CDs, TAD Mustards) and for me only the MKT1813 do retain the sound as close as possible to Mustards.
For later (PCB) Amps you can use MKT1822 or WIMA with WIMA sounding a bit more modern, HiFi-esque and edgier on crunch so if you want to trim e.g. a 2204 more brown use 1822, however YMMV....
I looked these caps up. 22000pf is the same as .022uf, right?
 

Spanngitter

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I looked these caps up. 22000pf is the same as .022uf, right?

Yes. 22000pf = 22nF = 0.022 µF

BTW: there is still NOS ERO/Roederstein MKT 1813 out there (green metallic color), these are also OK but they are getting scarce in the usual sizes used for tube amps and also outrageous in pricing.
Current Vishay/Roederstein production is yellow, sport a mark for the outer foil and are as good as the old green ERO MKT1813.
 

IANM

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Thanks for all the assistance along the way so far...
Here's some cleaning progress complete.

I am still in the process of sourcing all the required components. Looking like 2-3 weeks out from a first plug-in.

Update, it's a 67**H serial number but looks to be a transitional cab.

Praying the transformers still work...
 

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VERVEHAMMER

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Lay Down Mains! Allright!

(From my small experience) you have the only 3rd 1976 2203 Canadian I've ever seen.

Like your Adventure....
It's gonna be epic!:agreed:
 
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VERVEHAMMER

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Spannglitter, would you please post a pic or link of the exact capacitor(s) you were pleased with.

Thank you very much.

Truly appreciated.
 

Spanngitter

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Spanngitter, would you please post a pic or link of the exact capacitor(s) you were pleased with.

Vishay Roederstein MKT 1813 (Current Production)...available e.g. from Tube-Town, Mouser, Farnell, RS-Components, Buerklin, etc....
croe-400_8.png
 
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IANM

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Everyone, I want to thank you for all of the help so far.
Special thanks go out to those who are really invested in this project!
Parts are now ordered and I will update you all with the finished result.

I've got a horseshoe going on with my amp GAS, even more recently I just bought a 1977 - Marshall 1987 50w in like-new condition.

Bought it off the original owner and said he only plugged it in 2-3 times as it was "too loud".
How do we feel about this one?

Feeling blessed.
 

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Dblgun

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Everyone, I want to thank you for all of the help so far.
Special thanks go out to those who are really invested in this project!
Parts are now ordered and I will update you all with the finished result.

I've got a horseshoe going on with my amp GAS, even more recently I just bought a 1977 - Marshall 1987 50w in like-new condition.

Bought it off the original owner and said he only plugged it in 2-3 times as it was "too loud".
How do we feel about this one?

Feeling blessed.

Looks pretty clean, congratulations!
 

XTRXTR

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Bought it off the original owner and said he only plugged it in 2-3 times as it was "too loud".
How do we feel about this one?
Well the tolex that is in the pic looks clean but the aluminum knob caps are missing. I replaced all my knobs with brass guitar knobs because the Marshall knobs break too easy. I gig a lot so wear out is easy. I use the set screw as the tick mark. My amp cases look torn up.
 

VERVEHAMMER

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Amen!

SCORE!!!

:woot:

Outstanding in every way!

Congratulations.
 
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IANM

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I'll send reply tomorrow
Hello,
I am finally getting around to turning this thing back to spec.

On Thursday night I replaced the filter caps with success.

This is my first time trying to revert mods on a circuit board amp and have questions posed in photos before I solder the recommended changes into place.

Could you please review my photos and respond to the questions to ensure I understood the recommendations correctly and that I've set everything up in the correct place.

It would be greatly appreciated.
 

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neikeel

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I see the new bias caps, correctly orientated, but need snugging down to the board so that they are straight and I kink the wires over under the board into the trace and then solder.
I presume you are using 6550s?
 

IANM

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I see the new bias caps, correctly orientated, but need snugging down to the board so that they are straight and I kink the wires over under the board into the trace and then solder.
I presume you are using 6550s?
I will orient them in such a way that they're straight down to the board and will follow the instructions of tracing and soldering.

I was planning on leaving it set up with EL34s.

How are the couplers and diode looking?

Also the input jack situation leaves me wanting to remove the mods.

1651348648689.png
 
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neikeel

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The output couplers are fine.
Imo 82k grid leaks are far too small for EL34s an 0.022s.
You need at least 150k and ideally 220k for best bass response.
 

IANM

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The output couplers are fine.
Imo 82k grid leaks are far too small for EL34s an 0.022s.
You need at least 150k and ideally 220k for best bass response.
I really appreciate it, I have some 150k so I will start with those and will order some 220k to A/B afterward.

Do the 1N4007 bias diode and 27k resistor look proper as well? - I have both a 2w and 1/2w you'd use the 1/2 watt?

Lastly, if you have any guidance on the input situation I will them and thank your expertise!

Working through the retolex as we make the final decisions here.
 


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