Is my JMP all stock?

Discussion in 'Let's Talk Vintage' started by josep_cla, Aug 2, 2019.

  1. josep_cla

    josep_cla Member

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    I'd really appreciate your help on this one, guys.
    Just got a 1980 JMP 2203. I had to do it because it sounds glorious. It has "that" sound, specially with a SD1 or even a DS1 at low gain settings.

    Just noticed the chasis bolts are not original, so I opened it up and took some pics.
    The standby switch and the fuse holders have been replaced, that I can tell. The rest looks clean, but I not sure because I have no experience with this kind of amp.

    Thanks for helping!

     
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  2. neikeel

    neikeel Well-Known Member

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    Does not look bad at all. Obviously recapped (filter cans and bias caps).
    Rectifier diodes replaced with heavy duty 3A type (UF ?).
    The pi output caps have been replaced (normally 0.022uF probably increased to 0.047 or so got fatter bottom end?)
    Similarly the V1b bypass cap has been increased from 0.68uF to 1uF - probably a very subtle change. The tone stack cap has been changed to - can’t see what it is on my phone.
    Presume running EL34s? The bias feed resistor has been replaced with a 33k (usually 27k).
    Overall standard of work looks good.
     
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  3. josep_cla

    josep_cla Member

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    EL34s, yes.
    So many changes?!? Well, it sounds amazing, but sad to hear that is not stock, or even close...
     
  4. Nik Henville

    Nik Henville Well-Known Member

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    Here's the thing.
    Your ears can't hear originality.
    But your ears CAN hear excellent tone that makes you smile.
    So why on earth be sad that it's "not stock, or even close...". Just enjoy it.
    :hippie::pirate::uk:
     
  5. neikeel

    neikeel Well-Known Member

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    Important thing is that it sounds good and the work appears to be of a good standard so you can play it and not worry about it going bang.
     
  6. Lance Chambers

    Lance Chambers Well-Known Member

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    I agree with nei! Top tier work is worth it's weight in gold. You have a jewel..........rock n roll!:jam:
     
  7. josep_cla

    josep_cla Member

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    Sure thing, gents.
    I am gonna play this amp till the end of time. Sounds amazing. A bit less gain than the JCM800 y sold to fund it, but with much better tone.

    I wish it was all original, not gonna lie, but the sound is just perfect.
     
  8. boola1

    boola1 Active Member

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    It really is very close to stock.

    The only 2 things that change the tone are the pi output caps and the V1b bypass cap. The rest is just routine repair/maintenance stuff.

    You could easily get those 2 put back to stock if you wanted but as others said, it's very clean inside and if it sounds great, :jam:
     
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  9. josep_cla

    josep_cla Member

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    That is nice to know.
    Not gonna touch anything haha.

    Best 2203 that I eved had, and there have been quite a few...

    If you are curious, it is a 1980 unit.
     
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  10. boola1

    boola1 Active Member

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    My 2203 is also a 1980. It must have been a good year :)
     
  11. josep_cla

    josep_cla Member

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    Haha. I guess so.
    I should buy another one then...
     
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  12. 67Mopar

    67Mopar Well-Known Member

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    You mean, you're not going convert it into a metal amp? Aren't you going to install a PPIVM? What about upping the "fizz" cap, slope resistor, cathode bypass, and filtering values? What about clipping the bright cap? And what about installing a buffered effects loop? All metal amps have a buffered effects loop these days. Oh, and don't forget to squash the signal with an attenuator... That's the cherry on top!

    I'm just scratching the surface here. If you want to achieve class A douchebag status, these mods are mandatory.
     
    Last edited: Aug 6, 2019
  13. ampmadscientist

    ampmadscientist Well-Known Member

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    At least 3.
     
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  14. Drinkingdeath01

    Drinkingdeath01 Well-Known Member

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    Considering that its almost a 40 year old amp you've got a real jem on your hands. Over time some of the caps and resistors are going to be changed no matter what. Even tracking down a barn find type of JMP is still gonna need some freshening up. Rock it out and remember that we true players are all about tone, not museum quality peices that rot away behind a glass case.

    Congratulations on your new amp ! The JMP is one of my favorites.
    :applause::applause:
     
  15. josep_cla

    josep_cla Member

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    Thank you.
    It is the best sounding 2203 I ever played. Quite happy with it.
    Yes, I understand maintenance, but truth be told, my other "old" amps always came home stock: no refreshing whatsoever.
    But yes, it is 40 years old. It need some care.

    Just played it through a 4x12 with G12-65 and it just sings and screams...
     
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  16. josep_cla

    josep_cla Member

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    Although I appreciate the irony, you are making a mistake, gentleman: this IS already a metal amp.

    And for amps that are not metal, God sent us the Metal Zone.
     
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  17. Derek S

    Derek S Well-Known Member

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    A stock (or close enuff like yours) late 70's - early 80's JMP is on that short list of iconic amps IMO, the perfect crunch tone right outta the box, no fiddling needed.

    Congrats, hope it serves you well (or is it the other way around haha)!
     
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  18. josep_cla

    josep_cla Member

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    Thank you.
    I am quite enjoying it...
     
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  19. 67Mopar

    67Mopar Well-Known Member

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    :hmm: Okeydoke.
     
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  20. Emtbreid

    Emtbreid Active Member

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    Looks a beaut! There’s an ‘80 JMP for sale close by that I’ve been drooling over, but not possible to purchase now sadly.
     
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