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Marshall JPM-1 pre amp battery replacement?

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  • Marshall JPM-1 pre amp battery replacement?

    So my JMP-1 wont retain changes to programs when I shut it off. I figure the battery needs replacement. Much to my surprise it appears to be tack welded in place! I dont want to damage the contact. Any tips on changing out this battery? Thanks Bob
    "Reality is an illusion albeit a very persistant one " Albert Einstein

  • #2
    The tabs are tack welded to the battery, but are soldered to the PCB. Time for a tech.
    My rants, products, services and incoherent babblings on my blog.

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    • #3
      First, get out your voltmeter and measure the battery for charge.

      They make a number of the basic coin cells with the welded on solder tabs. You order them that way, you don;t weld them on yourself. Parts suppliers like Digikey have them.


      Or you can get a coin cell socket and mount that to the circuit board. That way you can buy plain old coin cells at Radio Shack and just pop them in the socket. Next time you ned a new battery, it will take just seconds to swap.

      I don;t remember the innards of that unit, so if it is a cylindrical battery instead of a coin cell, my apology. However those batteries are also available with the solder tabs welded on from the same sources.

      It is a 3v lithium cell.
      Education is what you're left with after you have forgotten what you have learned.

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      • #4
        Originally posted by Enzo View Post
        First, get out your voltmeter and measure the battery for charge.

        They make a number of the basic coin cells with the welded on solder tabs. You order them that way, you don;t weld them on yourself. Parts suppliers like Digikey have them.


        Or you can get a coin cell socket and mount that to the circuit board. That way you can buy plain old coin cells at Radio Shack and just pop them in the socket. Next time you ned a new battery, it will take just seconds to swap.

        I don;t remember the innards of that unit, so if it is a cylindrical battery instead of a coin cell, my apology. However those batteries are also available with the solder tabs welded on from the same sources.

        It is a 3v lithium cell.
        Yes its a coin cell. Kind of a PITA. I'll have to pull out the board to mount a holder or even put in a replacement the proper way. Geez... thanks Bob
        "Reality is an illusion albeit a very persistant one " Albert Einstein

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        • #5
          yeah well... Most times we have to do that to replace something on the board.

          How old is the thing, 20 years? In most stuff the memory battery lasts for years and years. SO accessibility is not much of an ongoing issue. Still, a socket would be even more convenient, I agree. I some some more recent synths have wised up that way at least.
          Education is what you're left with after you have forgotten what you have learned.

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          • #6
            Originally posted by Enzo View Post
            yeah well... Most times we have to do that to replace something on the board.

            How old is the thing, 20 years? In most stuff the memory battery lasts for years and years. SO accessibility is not much of an ongoing issue. Still, a socket would be even more convenient, I agree. I some some more recent synths have wised up that way at least.
            Yeah,18 years old. I found a battery holder for a slightly smaller battery and put it in place. It holds the memory now but some of the patches are stuck on zero volume and wont move-some work fine. To be honest I cant remember if it was like that before. Cant imagine why some patches do this and some dont? At any rate I only need about 5 patches so I guess I'll deal with it as is. Thanks Enzo and everyone else that responded. Bob
            "Reality is an illusion albeit a very persistant one " Albert Einstein

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            • #7
              Originally posted by rockon1 View Post
              Yeah,18 years old. I found a battery holder for a slightly smaller battery and put it in place. It holds the memory now but some of the patches are stuck on zero volume and wont move-some work fine. To be honest I cant remember if it was like that before. Cant imagine why some patches do this and some dont? At any rate I only need about 5 patches so I guess I'll deal with it as is. Thanks Enzo and everyone else that responded. Bob
              I would unplug it, remove the memory battery, discharge the power supply, leave it clamped and let it set a day. Then remove the crowbar, replace the battery, and power it up. That might give you a hard reset. Also, if you can find an owner's manual there may be a way to restore it to factory presets by pressing controls in a particular order. Another thing. If you have a scope look for excessive ripple on the power supply. It confuses anything digital.

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              • #8
                Originally posted by olddawg View Post
                I would unplug it, remove the memory battery, discharge the power supply, leave it clamped and let it set a day. Then remove the crowbar, replace the battery, and power it up. That might give you a hard reset. Also, if you can find an owner's manual there may be a way to restore it to factory presets by pressing controls in a particular order. Another thing. If you have a scope look for excessive ripple on the power supply. It confuses anything digital.
                Thanks olddawg! I tried the simplest suggestion first-the re-initialize thing . Fortunately the manual is the first thing that pops up on Google. Hold down the OD1 and Clean1 buttons while powering the unit up. All the patches work again! I think this pre will work well for my classic rock cover band. Has a lot of usable dirty tones and decent cleans too. I picked it up for 299$ last year at GC but havent really used it much so I think I'll give it a go! Bob
                "Reality is an illusion albeit a very persistant one " Albert Einstein

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                • #9
                  Originally posted by rockon1 View Post
                  Thanks olddawg! I tried the simplest suggestion first-the re-initialize thing . Fortunately the manual is the first thing that pops up on Google. Hold down the OD1 and Clean1 buttons while powering the unit up. All the patches work again! I think this pre will work well for my classic rock cover band. Has a lot of usable dirty tones and decent cleans too. I picked it up for 299$ last year at GC but havent really used it much so I think I'll give it a go! Bob
                  Glad to help. I picked up a 100 watt Line 6 Spyder amp a while back from a shop for $26. It was supposed to be hopelessly messed up. I looked up the owners manual and found the re-initializing instructions. It now works perfectly.

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