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  • Allen delay circuit

    My DIY Allen MDS-317 delay circuit for replacement of factory board.

    120 VAC relay connected to AC power this drops the 12VDC line on power off to avoid turn off thump.
    https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

    Adjustable DC delay circuit
    https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

    link to my Facebook page video
    https://www.facebook.com/dougaschult...ment&ref=notif

    The mechanical relay clicks when I change presets but it doesn't shut down the amps.
    I'm currently using 2 external power supplies, which I will replace.
    The internal supplies were blowing the mute relays on the AMP boards Allen wanted $75 a piece and I have 4 AMPs ouch.
    I bought replacements from Littlefuse for about $10 that's the next project.

    I would appreciate anyone's help with this.



  • #2
    H112man,

    Welcome to the Forum! It sounds like you have been having issues with your Allen, however, it would help to narrow things down if you provided the model of your organ, as the technology changed between instruments.

    Meanwhile, I know this topic has been addressed before, so you could search the Forum for the answer. However, we'll need the model of organ and/or amplifier before we can provide specific information.

    Again, welcome to the Forum!

    Michael
    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

    Comment


    • toodles
      toodles commented
      Editing a comment
      Michael: He said it is an MDS-317 (theatre model).

    • myorgan
      myorgan commented
      Editing a comment
      Thanks, Toodles. I added my request for forgiveness below.

      Michael

  • #3
    I'd be curious what voltage is on the delay line of the power supply inside the organ. It should be 12 volt delay. If it is blowing the mute relays you must have a lot more than 12 volts. Some organs may have 15 volts on the delay.
    Last edited by you795a; 02-21-2021, 12:08 PM.

    Comment


    • #4
      Ignore what I said above. It would have helped if I'd have read your first sentence!:embarrassed: Sorry.:-P

      Michael
      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

      Comment


      • #5
        Check out post no. 9 in this thread, as it gives a simple circuit to accomplish the time delay. https://organforum.com/forums/forum/...12v-time-delay



        Comment


        • h112man
          h112man commented
          Editing a comment
          Thanks that's where I looked first, I just wanted to try the adjustable delay relay.

      • #6
        Why would the relay click when a preset is selected?

        Comment


        • #7
          The relay clicks because there is a heavy load on the power when the stops are toggled, I'm assuming this is what's causing it to momentarily drop out. (that's another problem to look at) There was 15 volts going into the delay circuit and I measured 12.74 VDC going to the mute relays. With this new circuit I'm using an external supply of 15 VDC to trigger the time delay and 12 VDC from another external supply going to the mute relays on the AMP's.

          Comment


          • #8
            12.74 VDC should not be damaging the mute relays. Are you sure there isn't something else going on?

            Comment


            • h112man
              h112man commented
              Editing a comment
              That's what I thought too. I changed the 555 timer chip and put in a socket. I couldn't find the output device anywhere so I made my own delay with the parts listed above. The original delay worked with no load on it but when I tried it in the organ I started blowing out the mute relays. As you know it's a real pain to get that board out of the power switching box! I called Allen but they wanted to schedule a service call, and the relays would be $75 a piece from them. I asked to speak with a tech but I was offered a service call. The reason I bought this organ was so I wouldn't have to work on it all the time and play it more, hahaha. It does sound wonderful with 4 HC15 speakers. I've been ok for 2 days now so maybe I'm ok. What else would cause the mute relays to fail? I thought maybe old age the organ was built in 1994 and 1995.

            • h112man
              h112man commented
              Editing a comment
              The AMP that blows the mute relays is always channel 4 where the MIDI boxes connect. I had a Yamaha MU2000EX connected first, but recently replaced that with a Allen Ensemble. It seems like that's when the problems with the power off thump started, when I added the MIDI boxes, but I couldn't understand how that would start blowing the AMP's.

            • you795a
              you795a commented
              Editing a comment
              What kind of amps are in the organ? If you have the ADC amps, the delay should just connect from the power supply delay to the Mute terminals on the amps. If there are multiple amps the delay should be daisy chained from one amp to the another. It is odd that it is only blowing one relay and not all of them if it is something in the delay circuit. The organ should have an MCM board where the MIDI IN and OUT get connected and a MIDI power module a silver box) that has a 9 pin power connector and line in RCA connectors.

          • #9
            I don't see how the delayed 12V can help with a turn-off thump unless you can disengage it and mute the amp before the organ is powered down--it requires predicting a power-down--or, holding AC power "on" to the entire system for a second or so after the delayed 12V is dropped.

            The delay circuit in the Allen is to avoid a turn-on thump, not turn-off.

            Comment


            • you795a
              you795a commented
              Editing a comment
              The delay turns off immediately before the organ fully powers down. That is why there should be no power down thump. You might hear a slight noise but shouldn't be much.
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