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Thread: MDS Expander...

  1. #11
    Moderator jbird604's Avatar
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    Re: MDS Expander...



    Thanks Mark and Al for the suggestions. I'll take a look. However, the problem this one was exhibiting in the church was that it would repeatedly pop and go off, then reboot. It was kind of an endless cycle that it couldn't get out of.</P>


    To make matters worse, trying to disassemble it I broke the shaft off the volume control.</P>


    John</P>
    John
    ----------
    Church: Allen MDS-45 with Allen MIDI-DIVISION-II expander
    Home: Allen Renaissance R-230 with expanded four-channel audio and MIDI-DIVISION-II
    Shop: Bunch of organs in varying conditions, some good, some not...
    Half of an incredible two-man organ service team -- servicing all the major digitals in Arkansas churches
    https://www.facebook.com/pages/Birds...97551893588434

  2. #12
    ppp Pianississmo Beez5253's Avatar
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    Hello,
    Just installed a newly purchased MDS 212 D in my church. Organ works and sounds great but midi expander II is doing the same thing, repeatedly popping, going off, then rebooting every couple seconds. Is there a solution to this problem? I finally just unplugged the midi expander so I can still use the organ. I checked all connections to make sure they are secure but this didn't solve the problem. Hope someone can help.
    Mark

  3. #13
    Moderator jbird604's Avatar
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    Mark, I'll post here what I sent to you via PM. Perhaps others will benefit from this discussion:

    Very typical symptom, have seen it many times. (See my own posts above, from many years ago, first time I ran into this problem, and back when I didn't have any idea what was going on! Neither did the Allen dealer, who simply sold them a new unit. I eventually discovered that the old one worked just fine when driven by a proper power supply. Still have it, in fact.)

    The expander is drawing its power from the organ cage supply, which would be an MDS-PS-2 supply. The cage power supply should be adequate to power both the generator board and the expander, but when the supply begins to weaken, its voltage may drop a few tenths of a volt and the Expander will no longer boot up, just goes into an endless cycle, creating pops in the audio system. If you open the cage you'll see the power supply, which consists of a large transformer and a circuit board with all the diodes and caps and such, and some transistors mounted on a large heat sink.


    You might be able to make the expander work by doing some serious maintenance on the PS-2 circuit board, as follows: Gently wiggle the power connectors that attach to the PS-2, making sure all of them are snugly connected. If you see anything socketed on the board, press down gently to make sure it is well seated. Use a meter to test the 5 volt output (connect red lead of your meter to the 5 volt terminal on the side or top of the cage, black lead to ground terminal). Using a mini screwdriver, turn the 5 volt adjusting pot back and forth just a quarter turn or so, then set it to the point where you get 5.15 volts output.

    If you can solder, you might even try removing the circuit board from the cage and re-flowing all the large solder joints on the bottom, in case some of them have cracked over time due to heat and/or stress on the large pins.

    Check and tighten up all the connections between the cage and the Expander, particularly the power cables. I think it's good practice to unscrew the terminal strips, wipe the metal surfaces under the screws with a paper towel wet with WD-40 or some other solvent/lubricant, and re-connect. Anything that plugs in, such as the 9-pin cable that takes power to the Expander, should be pulled off and then re-plugged to assure a firm connection.

    If you have the ARTE module on this organ, it may also be drawing power from the cage, so if you don't use it you can try removing the power from it so that it won't be pulling down the voltage. That might be enough to let the Expander start working again.

    The real cure, which Allen prescribes, and which we do for every organ when we run across in this situation, is to replace the PS-2 power supply with a newer type that provides plenty of current. Allen is now shipping a very compact switching power supply to techs for that purpose. The way they ship it, it comes as a kit that has all the necessary adapters as well as detailed instructions. But they charge a few hundred dollars for that kit. If you have good skills with electrical and electronic equipment, you can use an inexpensive switching power supply to do the same thing, but you do have to make up your own wiring harness using the existing cables in the cage.

    I have done it successfully with a switching power supply that costs less than $25, available from several suppliers. But first try the maintenance and removing ARTE if possible. If that doesn't do it, you may have no choice but to replace the supply.

    Good luck!
    John
    ----------
    Church: Allen MDS-45 with Allen MIDI-DIVISION-II expander
    Home: Allen Renaissance R-230 with expanded four-channel audio and MIDI-DIVISION-II
    Shop: Bunch of organs in varying conditions, some good, some not...
    Half of an incredible two-man organ service team -- servicing all the major digitals in Arkansas churches
    https://www.facebook.com/pages/Birds...97551893588434

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