Cap Kit for a 2203

Discussion in 'The Workbench' started by Greg70, Aug 14, 2020.

  1. Greg70

    Greg70 New Member

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    I have a JCM800 2203 that I would like to replace the caps on. It has an inspection date of 7-11-84. It is the U.S. version with horizontal jacks and originally had 6550 power tubes. I replaced them with EL34's several years ago and rebiased. I have found capacitor kits from a few vendors that specify an early and late version of the 2203. Their early kits contain 6 large caps and 2 small ones. Their late kits contain 3 large caps and 2 small ones. My amp has 5 large caps in. Four are located between the large transformers and 1 is between two preamp tubes. I guess I can just buy the 6 cap early kit and have a spare cap? Was there a transition era between the early and late 2203's? It also has the pots on the circuit board if that helps in dating it.
     
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  2. StingRay85

    StingRay85 Well-Known Member

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    Check the values of the caps in your amp, and then buy the exact same ones. I don't have a clue about the variations but a 50+50 cap can replace two 50 uF caps, so takes up one space instead of two. If you want to keep things simply just make a list of all the caps you have and just buy them as drop in replacements
     
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  3. StingRay85

    StingRay85 Well-Known Member

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    And welcome to the forum of course :welcome:
     
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  4. Greg70

    Greg70 New Member

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    Thanks! I've been playing on and off for decades and dusted off my halfstack recently. It definitely needs a new master volume pot and the caps are original so I want to replace them before bad things happen. I'll be lurking around here for a bit.
     
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  5. Chris-in-LA

    Chris-in-LA Well-Known Member

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    Pots don’t go bad easily. Get some good contact cleaner for them. I use Deoxit Gold.
     
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  6. neikeel

    neikeel Well-Known Member

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    +1 on the Deoxit gold.
    Re the caps just replace like for like. I would use the F&T 500v ones for filter caps (big ones up top) and their bias caps will be good too the right size are 350v I think. Are you doing the work yourself?
     
  7. Greg70

    Greg70 New Member

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    Yes I'm doing it myself. I've worked on high voltage stuff before and know about using one hand and draining the caps. I modded the amp back in the 90s by adding an additional tube for an effects loop and swapped some resistors and caps in the tone circuit. I've got a good digital VOM but don't have an O scope, signal generator, or a variac.

    The main reason I'm going into it is because it started making a steady popping noise when I turn it on. It's at a steady rate of a pop every 3 seconds or so. It will fade away after a couple of minutes and then pop a couple of times after that. I guess it goes away completely after about 10 minutes. It doesn't get played much anymore and mostly sits but it didn't used to do this before. I know the caps are all original so I thought I would start with those.

    The master volume pot has always been very finicky. At around 1 it goes from practice bedroom volume to Madison Square Garden concert if I so much as breath on the knob. It's incredibly difficult to get something in between. It has a ton of static in it so I thought I would replace it. I have to pull the PCB anyway to get to one of the filter caps. I have deoxit. Will this definitely fix it? I just wonder if there's a bad spot on the pot in that position.
     
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  8. neikeel

    neikeel Well-Known Member

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    Normally a few squirts if Deoxit gold will revive most pots.
    Popping is often a preamp valve stropping.
    The cap job maybe a good idea but get it fixed first or you will be somewhat disappointed after your endeavours!
     
  9. South Park

    South Park Well-Known Member

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    Don’t forget to Clean your input jacks. Greetings from cal
     

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