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Allen MDS-35 piston issue

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  • Allen MDS-35 piston issue

    This morning I arrived at church to find all the pistons on our Allen MDS-35 messed up. I tried setting them up as I needed but everytime I switched to a different piston it would be different when I returned to the one I changed.

    Does anyone know what would cause this and what the solution is? I would reset it to factory settings but the manual doesn't explain how to do it. Any help would be appreciated!

  • #2

    Most likely, the battery pack is dead. Hopefully it hasn't leaked yet onto the capture board. There are several threads related to this issue on the Forum. Try searching for MDS-45 capture battery and see what you come up with.


    P.S. Try these threads: (obviously smaller than your organ, but it may give the information needed).
    Way too many organs to list, but I do have 5 Allens:
    • MOS-2 Model 505-B / ADC-4300-DK / ADC-5400 / ADC-6000 (Symphony) / ADC-8000DKC
    • Lowrey Heritage (DSO-1)
    • 11 Pump Organs, 1 Pipe Organ & 7 Pianos


    • #3
      To add to the discussion, I had a similar problem (erratic operation of Alterable Voices) on a board that had a previous battery leak. Hopefully there isn't any damage and when replacing the battery I would highly recommend relocating it and replacing/relocating the one on the alterable voice card as well for safety's sake.

      If there is an issue with the capture board, it may be possible to repair (I was able to get the AV board working on the MDS-45 I had at the time by repairing a trace that was broken by the battery acid).

      Allen MDS-41-S with MIDI-DIVISION-II
      Schulmerich Carillon Americana - 61 notes Flemish / Harp / Celesta / Quadra / Minor Tierce
      - MIDI Retrofit finally underway & Moller console in need of refurbishment
      Schulmerich Campanile Digital Carillon (Cast & Harp)


      • #4
        The capture memory on an MDS-35 is held by a lithium battery (not rechargeable) that is in a clip holder on the MN-1 board. Some later production MDS-35's might have a different MN board and a different battery, so look inside to see what type of battery you need.

        If it's the MN-1 board, the battery is a lithium type 123, available at Walmart or Walgreen's or most other places that have a good selection of batteries. This type was previously used in some cameras or in the flash attachments, so a photo store might be a good place to look if you don't find it at Walmart.

        If it's another MN board version, it probably uses the ubiquitous CR-2032, the coin-sized battery used in so many small devices these days. You can find them lots of places. I buy them on cards to keep in the service kit, a card holding 9 batteries costing under $10 at the hardware store. You might see one for $3 or so at Walmart or Walgreen's.

        Once you replace the battery, you might need to do the "reset" procedure that restores the factory parameters for MIDI, crescendo, tutti, and piston assignments. It should be in your owner's manual somewhere. If not you can call Allen Organ Co and they will email you the instructions.

        It's remotely possible that there is something else wrong with the MN board, but I'd sure try replacing the battery first.
        *** Please post your questions about technical service or repair matters ON THE FORUM. Do not send your questions to me or another member by private message. Information shared is for the benefit of the entire organ community, but other folks will not be helped by information we exchange in private messages!


        • #5

          Thanks for your replies! I wasn't able to locate the battery pack and I definitely did not want to mess around with it. (Electronics are not my area!) We had a technician come in and he said it was indeed the battery. He also said it was good we let him handle it, as other issues may have resulted from inexperienced meddling.

          There were some added benefits to having him take a look at it. The swell was louder than the great, so he regulated it and it sounds much better. Even the rattling caused by some pedal stops has greatly diminished. Perhaps the best part is that the organ is noticeably louder, so it can better lead the congregation.

          Hopefully the organ is set now for quite some time. Maybe at some point down the road I will be able to address issues myself.