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rebuild and modded marshall.

6/3/2000 9:18 PM
john hermsen
rebuild and modded marshall.
Hi everybody,  
Today I rebuild my trusty jmp mkII, witch I bought new in '82. I changed all the coupling and cathode caps for orange drops. Solderd out the 470pf cap across the volume. Changed the 10k cathode resister for 4.7k, the 33k slope resistor for a 47k. Then I changed the two 470pf ceramics for 270pf silver mica's.  
First impression, it's broken it doesn't hiss! Amazing how silent it is now. It has a bit more gain, a lot less trebly high can finally turn up the treble up. Mids are mutch nicer.  
I've read all these changes/mods here and would like to thank everybody for their input.  
6/13/2000 1:56 PM

"I've read all these changes/mods here and would like to thank everybody for their input."
The 4.7K cathode change is a value I always use and really like. I also favor the 47K slope resistor as well. You could also put a .68uF, 1uF, or 22uF in parallel to the 820ohm cathode resistor on V2A's cathode for a gain boost. You could also wire it to a switch to kick it in and out.  
Carl at Summit Amps had a JCM800 MOD schematic of mine on his site but I'm not sure if he still has it there or not...if so you can get some more ideas from that and of course tweak it until you are satisfied! :)  
Mostly it all depends on what sort of tone you are going after as to what mods would get you closer to the tones you want.  

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