JMP-1 preamp - battery replaced - still "E"

Discussion in 'The Workbench' started by MaxFrames, Jan 16, 2021.

  1. MaxFrames

    MaxFrames Well-Known Member

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    My JMP-1 MIDI preamp had a low battery problem (it often displayed "E" when powered on and sometimes, when it was not in use for more than one day, it would lose some of the settings). All this is hardly surprising because it still had its originaly battery, which means it was about 20 years old!
    So I brought it to a local tech to have a new battery installed, and I requested they fit in a socket and a removable battery so that I would be able to replace it myself in the future, without desoldering.
    I got the preamp back today, after about 40 days sitting in their lab. The tech said that when he opened it up he found the original battery had leaked onto the board. I suspect this may have been caused by the fact that they let the unit sit there unplugged for 40 days (they admitted having "forgotten about it" despite me calling them three times in the course of these 40 days) until yesterday when they finally got round to fixing it. Since the battery was already almost discharged, it may have finally given away and leaked when sitting there idle...
    Whatever the case, the preamp seems to work now, but when I turn it on, it sometimes still briefly displays "E" at power on (it did so three times out of 20 so far, after leaving it off for a few minutes). This should not happen, as the battery is brand new (I have proof; they have given me the old soldered battery back).
    Or perhaps the battery they fitted in was not fresh? I just hope the leaking did not damage the board or that they haven't done a sloppy work. What do you think?
     
  2. cruisemates

    cruisemates Active Member

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    Those things use a CR 2430 coin battery, so even if it did leak there was probably not a lot to clean up. They come in both standard and rechargeable forms. Here is a link to the rechargeable ones:

    https://www.amazon.com/Hillflower-LIR2430-Rechargeable-Lithium-Battery/dp/B07D1CH2Q7

    It looks like the rechargeable ones do need to be soldered in to work, and if they gave you some kind of holder for a non-rechargable then personally I would have gone with the rechargeable ones, even if it needed to be replaced by soldering it in, because non-rechargable coin batteries die in a matter of months usually.

    Do you know for certain whether they gave a rechargeable battery adapter, and if so, is a rechargeable battery currently installed? If so, the E sign is probably just a little leftover corrosion juice that needs to be cleaned up. And it should be. Do you have a way to look inside to see how clean it is?
     
  3. Michael Roe

    Michael Roe Well-Known Member

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    I had my battery done the same ( a new removable battery socket ) when mine needed a new power supply. I never got to the point it showed an "E".
    Does the "E" mean battery or possibly "Eprom". If my memory serves me correct, I think there is something about the preamp if you let the battery go totally dead you might have to have the eprom re-programmed??? Don't quote me on that....could be another preamp I am thinking of??
     
  4. cruisemates

    cruisemates Active Member

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  5. Dogs of Doom

    Dogs of Doom Moderator Staff Member

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    you also need to do a reset, there's a thread on here somewhere...
     
  6. MaxFrames

    MaxFrames Well-Known Member

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    I asked a removable battery slot to be installed, so I'm pretty sure it's a non rechargeable, regular CR2032. I will perhaps open the unit if it displays an E again.
    As per the manual, that stands for "low voltage on the backup battery" and anyway the first thing I did when I got the unit back was resetting it to factory settings.
    I will see how long this cell will last, I hope at least a year or so.
     
  7. MaxFrames

    MaxFrames Well-Known Member

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    No way... after 30 minutes unplugged, it showed the E.
    Settings apparently still there, but will they be there tomorrow?
    So
    1. Either I was wrong in what I read and replacing the battery with a socketed rechargeable one was not feasible
    2. Or the tech messed up something
    3. Or the acid leak damaged something
    I'm devastated
     
  8. Dogs of Doom

    Dogs of Doom Moderator Staff Member

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    look here, if you need, revisit the whole thread...

     
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  9. MaxFrames

    MaxFrames Well-Known Member

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    I did that reset multiple times.
     
  10. Dogs of Doom

    Dogs of Doom Moderator Staff Member

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    you unlocked it 1st?
     
  11. Michael Roe

    Michael Roe Well-Known Member

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    Doing #1 is definitely feasible....mine has been fine for about 4 years now after having that done.

    EDIT: Mine does not have a rechargeable battery but just a standard battery.
     
    Last edited: Jan 16, 2021
  12. Michael Roe

    Michael Roe Well-Known Member

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    You might want to bring it to another competent tech to check it out.
    Make sure they check the power supply. When those go bad there are all sorts of issues.
    Mercury Magnetics makes one that drops right in and works great.
     
  13. MaxFrames

    MaxFrames Well-Known Member

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    The unit was not locked, the resets worked fine.
    Good to know that the refit is feasible, though they chose to use cr2032 instead of cr2432, dunno why.
    After letting it sit unplugged overnight, this morning it turned on without the E.
    So it's erratic...
    The power supply: what I can tell you is that mine is really noisy and buzzy.
     
  14. MaxFrames

    MaxFrames Well-Known Member

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    No E so far today. I had a thought. What if they actually fitted a rechargeable, and it was still not fully charged? What would be the implications if if was a reachargeable (in a socket, not soldered)?
     
  15. MaxFrames

    MaxFrames Well-Known Member

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    I've taken some time to read the JMP-1 User Manual all over again. The paragraph about the backup battery seems to imply that the check routine that is executed upon powering the unit up may not be a voltage check on the battery as I was convinced it was (which would be orthodox and make perfect sense) but some kind of checksum routine over the EEPROM data. If this is the case, then the "E" would not necessarily mean "low battery" but rather "corrupted settings" which can be caused by different things, including but not limited to a bad/low battery (stale data, which a reset would have cured, or electronic damage).
    So again the ghost of the leaked acid is rearing its ugly head in my head.
    Let's hope for the best...
     
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  16. Michael Roe

    Michael Roe Well-Known Member

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    When my power supply was going bad the only thing I noticed was that all of a sudden it started to lose volume on only the OD channels. At first I thought that maybe I had accidentally flipped one of the +4/-10 db switches on the back. Funny thing right before mine did the volume drop thing, I had just gotten IK's Amplitube 4 plugin and was playing around with their model of a JMP-1. I was doing some comparisons to see how close it was to the real deal, like setting them both to identical settings. With their plugin the volume on the OD CHs reacts just like mine did when the PS was going bad.
     
  17. MaxFrames

    MaxFrames Well-Known Member

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    I never had that symptom. The only possible sign of a PSU problem is a rather noticeable buzzing (which translates to a humming that's distinctly audible at high volume, the typical mains hum, I think it's 50 Hz here in Europe) from the unit.
    If I place my hand on the front bezel, I can feel it vibrating slightly.
    I can't recall if it has always done it.
     

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