Dating my JMP50

Discussion in 'Let's Talk Vintage' started by obx351, Mar 22, 2015.

  1. obx351

    obx351 Member

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    I am sure this has been asked many times on this forum but I've recently purchased a plexi jmp50 and 8x10 cabinet. Can anyone venture a guess as to the date of this plexi and cabinet?

    I am not sure if it's a late '67, '68 or an early '69. I think the cabinet is a '68? It has a gold logo. Anyone??

    As you can see the amp needs to be cleaned up a bit to get rid of the surface dirt but it's supposed to be all or mostly original. It's been sitting in my buddy's basement for at least 20 years and he may have had it longer. But the cool thing is that it was the first Marshall I ever played and I am pretty psyched I was able to get it.

    Anyway any help dating it would be appreciated!!

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  2. janarn

    janarn Well-Known Member

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    11-series 50w Plexi is typical '68,
    but you will have to show gut shots to be sure.
     
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  3. obx351

    obx351 Member

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    I am going to give it to my amp guy this week or next and I'll get him to take gut shots for me. I'll post them when I get 'em. Thanks for the info!
     
  4. Ace Major

    Ace Major Member

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    Awesome gear dude!
     
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  5. dash8311

    dash8311 Well-Known Member

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    Whatever year it is, that's a great score!
     
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  6. Joshabr1

    Joshabr1 Well-Known Member

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    Beautiful. I'm with janarn 11series usually 68. Post some gut shots please.
     
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  7. TAZIN

    TAZIN Active Member

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    As mentioned, most 11series 50w amps are '68's but there are some that are early '69's also. Have your amp guy take pictures before replacing any parts since they can help aide in determining a year of mfg more precisely. Likewise, if any parts are replaced make sure you get the originals back too.
     
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  8. rick16v

    rick16v Well-Known Member

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    I thought this thread was going to be about when a man loves his Marshall too much...
     
  9. neikeel

    neikeel Well-Known Member

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    Absolutely
    Also make sure your tech is on board with sympathetic restoration of a vintage amp. You do not want to hand him a 68 JMP50 and have him hand you back a 1987X.................................
     
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  10. obx351

    obx351 Member

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    First off thanks for all the comments!!

    My amp guy is a great guy and very above board. He'll do the right thing and let me know beforehand. He also takes the time to explain to me the whats and whys as well as giving me options. He explains everything before he does the job and does great work. His name is Burke Hunn, http://www.hunnamps.com/ and I have complete faith in him.
     
  11. neikeel

    neikeel Well-Known Member

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    Glad you have found a good tech.

    It is worrying how many bad ones tell you that your OT or PT is duff and all of your original mustard coupling caps have failed (they virtually never do!) and your amp comes back with a shiny new Merc Mag OT and Sozos across the board which halves the value of the amp, and in respect of the OT changes the tone irretrievably. Mysteriously they 'lose' the parts (ie sell them on - a 60s Drake 784-139 OT will go for over $500) rather than give them back to you.
    Now big blue filter caps on an amp that has been sitting in an unused amp for years are a different matter..afraid they can be reformed with a Telomike or a variac and other methods but if the amp was powered up they are probably toast:ugh:
     
    Last edited: Mar 24, 2015
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  12. obx351

    obx351 Member

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    I am going to have my amp guy give it a once over a just to make sure. But I don't think there's much wrong with the amp - maybe a resistor or a cap. Anything needing changes will get period correct NoS parts.
     
  13. allwheelz

    allwheelz Well-Known Member

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    Great looking amp and cab!!!!! And that's awesome that you've got a great tech to help you with it. I gotta drive an hour just to get to anybody so I've been learning as I go with help with from fellow mf'ers. Hope everything checks out ok for ya, and I bet that cab sounds killer!!!!
     
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  14. Jaymz E

    Jaymz E Well-Known Member

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    I'd take my own pics of the guts first. If those transformers are still good they would be like a pair of kidneys on the black market for some techs.
     
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  15. obx351

    obx351 Member

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    I get it but my amp guy is not going to steal them.
     
  16. sct13

    sct13 Active Member

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    Wow, I have a similar one....

    its a 10 series....where does that fall?

    Nice cabinet! Cant wait to see the insides of this one!
     
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  17. TAZIN

    TAZIN Active Member

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    S/10xxx ---> typically 1967-1968.
    S/11xxx ---> typically 1968.
    S/A10xxx ---> typically 1969.
     
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  18. sct13

    sct13 Active Member

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    thanx Tazin...

    I was wondering because many parts are dated much earlier 65' and 67'

    I wonder if it sat around the factory before it was finished and shipped....who knows....Great amp.


    Waiting on your gut Shots OP !
     
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  19. TAZIN

    TAZIN Active Member

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    It's not uncommon to see '65 and '67 signal capacitor date codes in '69 plexi panel 50w amps. Here's a brief list showing some of the typical dates codes:
    WIMA TFM 0.022uF/400v ---> B8
    Mullard 0.022uF/400v ---> D7W or D8N
    Mullard 2200pF/400v ---> D7N or D7W
    Mullard 0.1uF/400v ---> C8N or D8W
    Mullard 0.1uF/160v ---> D7N
    Mullard 0.68uF/160v ---> C5N
    WIMA 0.68uF/100v ---> 768 or 868

    When the early metal panels start to arrive you start to see more of these date codes:
    Metal panel Mullard 2200pF/400v ---> D8W
    Metal panel Mullard 0.68uF/160v ---> D8W
     
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  20. sct13

    sct13 Active Member

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    Thanx Taz, definitely some of those on that list, are on that board.
     
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