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  • ADC 2000 Keying problem

    We have a Christian school here in town with an ADC 2000 in their auditorium. Lately it has a keying problem where several notes may not play up and down affecting all three divisions.

    The problem comes and goes, however when it occurs you can hear faintly in the background what sounds like several keys being mashed down all at once. The sound is fairly faint in the background but is always there when the keying problem is present.

    I have replaced the KA-1 board already, so I am inclined to believe the problem may be in the MUX board. Has anyone else experienced this type of problem and have some suggestions where I might look.

    Bye the way I have checked the power supplies and they seem to be in order.

    Any suggestions will be greatly appreciated as I know very little about these organs.

  • #2
    Is it always the same notes that don't sound?

    An improperly seated pedal board can result in polyphony issues that will result in notes not playing. Although from your description it doesn't sound like that's the problem, detaching the pedal board is something that's easy to do to eliminate it as a possible cause.
    -Admin

    Allen 965
    Zuma Group Midi Keyboard Encoder
    Zuma Group DM Midi Stop Controller
    Hauptwerk 4.2

    Comment


    • #3
      Originally posted by Admin View Post
      Is it always the same notes that don't sound?

      An improperly seated pedal board can result in polyphony issues that will result in notes not playing. Although from your description it doesn't sound like that's the problem, detaching the pedal board is something that's easy to do to eliminate it as a possible cause.
      We already tried removing the pedal board with no help. It is not always the same notes. Sometimes it is a few notes here and there, and at other times it is most of the notes on the keyboard. From one moment to the next the missing notes will change. This seems to be a multiplexing problem, thus making me suspect the USCM-1 board. My initial thought was the KA-1 board, but changing that did not solve the problem. The soft background sound like several notes playing seems to make me thing that the mux board somehow has a "leaking chip" that makes it seem like those notes are being sent to the cage. Also all of a sudden the "background noise" will go away and the organ plays perfectly!

      Comment


      • #4
        Have you already done all the "routine maintenance" things we have discussed so much on this forum RE: Allen ADC organs? -- cleaned, lubed, re-seated every connector, every cable, every lug, everywhere in the organ where any thing is disconnectable? Have you pulled each board out of the cage, cleaned and lighted lubed the card edge connector, then re-inserted gently but firmly? Exercised every mini-pot and other control?

        General routine maintenance takes care of a TON of issues with the ADC models, which are now getting up there in years.
        John
        ----------
        *** 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!

        https://www.facebook.com/pages/Birds...97551893588434

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        • #5
          Yes John, all of the plugs on the USCM-1 board were exercised as well as all of the boards in the cage. Power supply voltages were checked, however it has occurred to me that they may have been checked when the organ was intermittently working. I want to re-check them when it is acting up just to be sure. I have located a spare mux board and will try that next. The board is an E*#y purchase however it came from the 'service kit' of a dealer who went out of business and as near as I can tell it was never installed. Not a speck of dust on it and it is a 2004 mfg date.

          I really appreciate you guys giving this some thought as the collective knowledge of all on this forum is a powerful tool!

          Thanks

          Comment


          • #6
            Don't overlook the possibility of a wiring fault in the vicinity of the keyboards. I once had an ADC model acting very strangely and finally discovered that a bundle of wires had been nibbled by a mouse but not gnawed through. There was enough exposed copper that the wires might short together intermittently when the keyboards were touched. I fixed it by unbundling the cable bundle, spreading the damaged wires apart, and wrapping tape around the bare spots.

            But changing out the USCM is certainly something to try. Also check the 5 volt free-standing power supply in the floor of the console that provides the operating voltage for the USCM board.
            John
            ----------
            *** 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!

            https://www.facebook.com/pages/Birds...97551893588434

            Comment


            • #7
              Thanks John...I didn't think of looking at the wiring for possible shorts in an instrument this old.

              In searching other threads I saw something regarding pulling the EG boards and re-inserting them one at a time. WITH THE POWER OFF of course :-) I guess I don't understand what envelope generators would have to do with keying, but I'm up for trying anything.

              I did check the +5 supply, but it may have been when everything was working. I'll be sure to look at it next time it goes crazy, voltage may be drifting.

              We'll keep you posted

              Comment


              • #8
                According to Allen tech service, the USEG boards can be pulled loose but NOT re-seated with the organ powered up. Early on in the ADC era it was found that the EG boards could cause problems in the cage that seem totally unrelated to Envelope issues, and could affect organ divisions besides the division a particular EG board was providing envelopes for.

                So, it was suggested that we pull out the EG boards one at a time and see if a problem clears. If removing a certain board seems to clear the problem, then that board may be the cause of it. (The organ will play without the EG boards, but notes lack their characteristic attack and decay slopes, will simply be fully on and fully off, like the tones of a Hammond.)

                No need to push the EG boards back in during this testing. Just pull one out, see if the problem went away. If so, that is the bad one. If not, then leave that one out and pull out another one, etc.

                You may be right though to suspect the USCM. Especially with the trouble moving around randomly, that sort of seems like a USCM thing. I hope that fixes it.

                If not, even more extensive cleaning and maintenance could be needed, even to the extent of removing the cage from the console, taking off the back cover, and looking for issues in the web of wire on the back of the backplane board. Also, individual cage boards may need to have their EPROMs removed, legs and sockets cleaned out and lubed, etc.

                BTW, if this organ has a card reader or if it used to have one, there was originally a battery pack on the USAV board, and if it ever leaked, there could be residual battery damage to the backplane. This is what brought my MDS-45 at church down a few years back, and it was a nightmare to repair. But you should look carefully at the slot where the USAV board is or was installed, if it ever had one.
                John
                ----------
                *** 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!

                https://www.facebook.com/pages/Birds...97551893588434

                Comment


                • #9
                  Originally posted by jbird604 View Post
                  Have you already done all the "routine maintenance" things we have discussed so much on this forum RE: Allen ADC organs? -- cleaned, lubed, re-seated every connector, every cable, every lug, everywhere in the organ where any thing is disconnectable? Have you pulled each board out of the cage, cleaned and lighted lubed the card edge connector, then re-inserted gently but firmly? Exercised every mini-pot and other control?

                  General routine maintenance takes care of a TON of issues with the ADC models, which are now getting up there in years.
                  My problem is that several adjacent notes on all three manuals don't work. Any suggestions?

                  Comment


                  • #10
                    WOW...thanks for the run down on the EG boards. I never would have guessed that they might be related. It certainly won't take long to pull them one at a time to see.

                    Due to the age of this instrument, it might be useful to pull everything apart and check the backplane on the cage as well.

                    John I so appreciate the detail that you and others here on the forum provide, in helping to keep these old Allens in faithful service to our communities.

                    Comment


                    • #11
                      When this happened with my ADC-5400, I replaced the board John is talking about, as well as the AP (Audio Processor) board. To date, I don't know which board solved the problem, but it did. It was at the beginning of a Symphony rehearsal, and I didn't play until the 3rd movement, so replaced both the boards, and was in business. I never had a chance to problem-solve after the concert to find out which board was the culprit, so I just left well-enough alone.

                      Hope this helps.

                      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


                      • #12
                        Originally posted by myorgan View Post
                        When this happened with my ADC-5400, I replaced the board John is talking about, as well as the AP (Audio Processor) board. To date, I don't know which board solved the problem, but it did. It was at the beginning of a Symphony rehearsal, and I didn't play until the 3rd movement, so replaced both the boards, and was in business. I never had a chance to problem-solve after the concert to find out which board was the culprit, so I just left well-enough alone.

                        Hope this helps.

                        Michael
                        Michael,

                        Was it the USEG board or the USCM you changed other than the Audio Processor?

                        Thanks,

                        John R

                        Comment


                        • #13
                          Originally posted by Jramsey View Post
                          Was it the USEG board or the USCM you changed other than the Audio Processor?
                          John,

                          It was in the cage, so it wasn't the USCM. Most probably the USEG (I can check), but I can't vouch for that. I do know the issue took down the entire organ intermittently.

                          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


                        • #14
                          Jake Dwyer (post #9 above) -- the problem you describe would be due to a single wire being broken somewhere in the keying lines or bundles. The Allen keyboards are multiplexed -- only about 16 or 20 wires total run to the entire keyboard stack to detect all the keying. They are usually small, thin, white wires, and you will see them zip-tied to the switch pc boards, looping from one keyboard to another.

                          The keying works by assigning the keys in groups of six (I think it's six). For example, the notes middle C through middle F constitute a single "group" and that group are all connected to the same group wire, even on the other manuals of the organ. To distinguish among them, there are also a set of data wires that run to the individual key switches, but if you study the system you can see that it only takes a small number of these to cover all the keys. Thus, the multiplexing system needs very few wires in order to determine which keys are down at any given instant in time.

                          I may not be describing the system exactly as it appears, but you get the idea. A single broken wire somewhere between the keyboard stack and the multiplexer or KBA board will cause six notes to be dead in all divisions.

                          So you should trace all the wires that lead from the keystacks to the circuit board. Check the large multi-pin plug that connects these wires to the multiplexer board, making sure it is firmly pressed into place. check to be sure all the wires are tightly wrapped on the pins, and neatly soldered to the key contact rails.

                          If the fault is not in the wiring itself, it could be in a detector chip on the multiplexer board. But there's at least a chance it is just a broken wire. I went out once to check a problem like this and found that a critter had gnawed a wire in half.
                          John
                          ----------
                          *** 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!

                          https://www.facebook.com/pages/Birds...97551893588434

                          Comment


                          • #15
                            John,

                            It looks like it was one of the EG boards. The first one I unplugged brought the organ back to life. I moved its eprom over to the replacement board, plugged it back in, and the organ came up perfectly. In fact it may be my imagination, but I think the instrument actually sounds better. We played it for over half an hour and everything worked perfectly. I'll let you know if it turns out the 'fix' is not actually real, but from what I have seen today, I think we got it!

                            Thanks again so much for your help and all of the community here on the forum.

                            Comment


                            • jbird604
                              jbird604 commented
                              Editing a comment
                              That's great!

                          Hello!

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