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Roland JC120 early model schematic anyone?

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  • Roland JC120 early model schematic anyone?

    I'm looking for an early JC120 schematic. I have looked around online and I already thought I had all the schematics - but not this little devil.

    s/n 471557

    It has a separate board for the delay/chorus, and two further more or less identical boards, one for each channel. So not the usual large single board for Channel 2 plus effects.

    The channel boards have mostly discrete transistors, only one IC each, a little 6-leg round case job. The discrete-transistor schem that's readily available has two FETs as the first stage, whereas this has a 2SC1681 then a 2SA493 (though there are 2SK30A fets further in).


    The amp is in a dreadful state but I managed to get Channel 1 up and running, and the output stages are fine. Ch2 goes silent at the first stage because the bias is off, shotgunned a few transistors but there's something a bit further in gone wrong and it is hard to trace without the schem. I would be deeply grateful...

  • #2
    Hey presto !!

    the zipped pdf failed to upload - its the 3rd edition surprisingly!

    Title is "JC-120_3RD_SM.pdf" and almost 10 megs.

    Channel 1 first 2 transistors 2SC 1000GR and 2SA 493GR

    Ill look into it.

    EDIT:Finally found all 18 pages at Black Magic Amplifiers under a different title.

    Roland JC-120, JC-160 (79-3) Jazz Chorus Service Manual.pdf

    http://bmamps.com/Schematics/Roland/...e%20Manual.pdf

    There's one here but you have to speak Spanish and be a member!


    Busco Roland KC 350


    Maybee Vintage Kiki we should have a Roland schematics collection?

    Roland recently had a promo on "40 years of Roland JC"

    Roland - 40 Years of Roland Jazz Chorus

    From this there's a basic time line

    1975-- JC-120
    JC-60
    1976-- JC-160
    JC-80
    1978-- JC-200(S)
    JC-50
    1984-- JC-120H
    JC-77
    1986-- JC-65
    1992-- JC-20
    1996-- JC-85
    1997-- JC-90
    2015-- JC-40

    Teemuk has it here if you're a member
    http://www.ssguitar.com/index.php?topic=2243.0
    Attached Files
    Last edited by oc disorder; 06-22-2016, 10:38 PM.

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    • #3
      Roland jc120 schematics 1976-84

      http://music-electronics-forum.com/t17368/#post141921
      It's All Over Now

      Comment


      • #4
        Many many thanks oc disorder. That's the one! It doesn't seem to be on the page vintagekiki linked - here's the link again for clarity:

        http://bmamps.com/Schematics/Roland/...e%20Manual.pdf

        very useful for early models with discrete transistor preamps

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        • #5
          Well, now we have a dead link and a file that is too large to upload.
          Can anyone break it into pieces and repost?
          (JC-120_3RD_SM.pdf)
          Originally posted by Enzo
          I have a sign in my shop that says, "Never think up reasons not to check something."


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          • #6
            Is it any of the ones on post #2 of this page?

            http://music-electronics-forum.com/t17368/#post141921
            "I took a photo of my ohm meter... It didn't help." Enzo 8/20/22

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            • #7
              Originally posted by g1 View Post
              Well, now we have a dead link and a file that is too large to upload.
              Can anyone break it into pieces and repost?
              (JC-120_3RD_SM.pdf)
              I had this version of the schematic up on my dropcanvas account a while back. Here it is...
              dropcanvas - instant drag and drop sharing - Roland JC-120 3rd sm
              When the going gets weird... The weird turn pro!

              Comment


              • #8
                Index of schematics Roland

                http://www.tangible-technology.com/schematics/Roland/?MA

                JC-120_3RD.pdf
                JC-60_80_120_160_SM.pdf
                JC120 2nd.pdf
                SM_JC-120 4th.pdf
                SM_JC-120 5th.pdf
                SM_JC-120_11016.pdf
                JC120UT_JT.pdf
                SM_JC-120_11052.pdf
                It's All Over Now

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                • #9
                  This is an attempt to attach this (Too Large) file onto MEF. I believe now that file size limits have expanded thus allowing this file to be uploaded to the database here. It can be found on the link that Vintagekiki attached too. The dropcanvas people dropped off the Internet so now the file I linked to is dead. Main point here is to have the file directly at MEF so we don't have to depend on any 3rd party website to host it.
                  Attached Files
                  When the going gets weird... The weird turn pro!

                  Comment

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