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thomas monticello 371 some keys not working

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  • thomas monticello 371 some keys not working

    I have a thomas monticello 371 some keys not working.
    What is the recommended way of cleaning these key contacts?

    Thanks,
    nosaj

  • #2
    The solo keyboard used DC keying so you can use Deoxit D5 from Caig labs. Same for the coupler contacts on the Accomp manual. Do not use D5 on slide controls.

    The voices on the accomp manual use audio keying through black vinyl buss bars. They can be cleaned with denatured or 91% isopropyl alcohol. Better still is Fader Lube F5 spray from Caig labs. Also use F5 on the slide volume controls. Do not use D5 on vinyl buss bars.

    A common issue also is the plug-in tone generators. They are held down by a 1/4" hex head screw. Remove the screw, unplug the generator then plug them back in.
    td
    Last edited by tucsondave; 07-21-2021, 05:39 AM.

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    • #3
      An organ from this era (early 1970’s) probably has busbar style keyboards. Usually you can take the top off somehow, then rotate the keyboards upwards along the hinge at the back. You can clean the busbar and the switch leaf that connects to it with deoxit, (spray a bit on a swab or clean cloth is better than spraying directly) and also adjust them if they have somehow stopped touching, but I think it is unlikely to be the source of your problem.

      More likely is that the power supply is faulty, and the extra current has damaged one or more of the tone generator boards, and/or some components on the tone generator boards have given out. Given that, I would check the power supply to make sure the voltages are good and there is no AC ripple. Even if they check out, replacing the capacitors is not a bad idea for an organ of this age. If you’ve never done that before, refer to the safety sticky. If it’s the tone generator boards, they can be repaired, but it’s a more involved procedure.

      Another recommended tip is treating all the removable connectors in the organ with deoxit, in case it is corrosion that is causing the problem (also unlikely to help, but it’s worth a try).

      Comment


      • #4
        Originally posted by Larason2 View Post
        An organ from this era (early 1970’s) probably has busbar style keyboards. Usually you can take the top off somehow, then rotate the keyboards upwards along the hinge at the back. You can clean the busbar and the switch leaf that connects to it with deoxit, (spray a bit on a swab or clean cloth is better than spraying directly) and also adjust them if they have somehow stopped touching, but I think it is unlikely to be the source of your problem.

        More likely is that the power supply is faulty, and the extra current has damaged one or more of the tone generator boards, and/or some components on the tone generator boards have given out. Given that, I would check the power supply to make sure the voltages are good and there is no AC ripple. Even if they check out, replacing the capacitors is not a bad idea for an organ of this age. If you’ve never done that before, refer to the safety sticky. If it’s the tone generator boards, they can be repaired, but it’s a more involved procedure.

        Another recommended tip is treating all the removable connectors in the organ with deoxit, in case it is corrosion that is causing the problem (also unlikely to help, but it’s worth a try).
        I'm familar with amplifiers and power supplies. First things first I'm rebuilding the power supply then I'll look at the tone gen boards. The only complaint was a few keys on the lower register not working. When i picked it up Customer tried to show me the issues but vol was super low. So first thought was power supply. He bought it for his daughter new and she learned on it , now he's getting up in age and wanted it repaired to give back to her.

        It's not my first rodeo in repairing an organ but I've never had to clean the contacts with the buss bars and vinyl strips.
        nosaj

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        • #5
          Originally posted by tucsondave View Post
          The solo keyboard used DC keying so you can use Deoxit D5 from Caig labs. Same for the coupler contacts on the Accomp manual. Do not use D5 on slide controls.

          The voices on the accomp manual use audio keying through black vinyl buss bars. They can be cleaned with denatured or 91% isopropyl alcohol. Better still is Fader Lube F5 spray from Caig labs. Also use F5 on the slide volume controls. Do not use D5 on vinyl buss bars.

          A common issue also is the plug-in tone generators. They are held down by a 1/4" hex head screw. Remove the screw, unplug the generator then plug them back in.
          td
          I've got Fader Lube on hand and CRC electrical contact cleaner and some 91% alcohol.
          Thanks again for the great tips.
          nosaj

          Comment


          • #6
            When I serviced those vinyl coated busbars, (Elasomer) I would remove the vinyl from the metal busbar rod. Then clean that metal with a polish like Brasso, clean off the residue and leave a light coating of DeOxite D5. It seemed the metal would get a coating of tarnish that would interfere with signal conduction. Cleaning the rod vastly improve keying.

            The vinyl was there to provide a "soft keying" by conducting the signal depending on pressure. When first touched by the contact, a very small amount of signal would pass. As the contact pushed harder, more signal passed until the key was fully depressed. If you removed the vinyl, you would actually improve the keying but introduce the key click sound found in most audio keyed systems like the Hammonds.

            Geo

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            • #7
              Originally posted by geoelectro View Post
              When I serviced those vinyl coated busbars, (Elasomer) I would remove the vinyl from the metal busbar rod. Then clean that metal with a polish like Brasso, clean off the residue and leave a light coating of DeOxite D5. It seemed the metal would get a coating of tarnish that would interfere with signal conduction. Cleaning the rod vastly improve keying.

              The vinyl was there to provide a "soft keying" by conducting the signal depending on pressure. When first touched by the contact, a very small amount of signal would pass. As the contact pushed harder, more signal passed until the key was fully depressed. If you removed the vinyl, you would actually improve the keying but introduce the key click sound found in most audio keyed systems like the Hammonds.

              Geo
              Awesome without being told stuff like that I would never have discovered.
              Thanks so much
              jason

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              • #8
                Got the Power supply an amplifier recapped. No audio from the keys but hook an mp3 player up at tape input I get audio. So I'll reseat the tone boards tomorrow and see where we're at.
                nosaj

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                • #9
                  Evidently i only got the power supply for the power amp done. There is a PC Board power supply in pics. Wondering if someone knows how the boar comes down so I can change the caps on it without removing all the wires connected to it.Click image for larger version

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                  • #10
                    It looks like there are screws at the edges of the boards, but still, even if you remove those, it won’t be an easy task to label and desolder all the wires going to the board. What you might be able to do is desolder and/or disconnect the whole assembly that lifts up from the other components, and move the assembly to your bench for recapping. Otherwise, you can always just loosen the screws, pull out the board as far as the wires will let you, and recap in place. I hate doing that too, but sometimes there is no other option.

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                    • #11
                      There is no need to unsolder any wires on the Thomas circuit boards. Remove the black card edge guide from the lower edge of the board then pull the board out of the upper guide and fold it up.
                      But why?
                      Have you measured the voltages from the Amp / power supply? You said you had keyboard sound before you recapped the amp but not after.
                      Do you have 23 volts between N3 and N21 on the power supply board? Left most board in the second photo.

                      td

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                      • #12
                        The volume was super low barely audible. Now key will just click(you can hear it in the amp) There is no DC at the Speaker terminals. Inputing signal at main or tape input sounds fine. Poweramp is good. Between N3 and N21 I get 2.2 volts. Habit for me especially on stuff of this age has always been recap the power supplies then work your way around. Once this leaves my house I don't intend to keep working on it. But since power supplies always do the heavy lifting so to speak is why I recap them.
                        Thanks,
                        Jason
                        Will follow up with voltages after this board is done( gotta see what caps I have on hand.

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                        • #13
                          Originally posted by tucsondave View Post
                          There is no need to unsolder any wires on the Thomas circuit boards. Remove the black card edge guide from the lower edge of the board then pull the board out of the upper guide and fold it up.
                          But why?
                          Have you measured the voltages from the Amp / power supply? You said you had keyboard sound before you recapped the amp but not after.
                          Do you have 23 volts between N3 and N21 on the power supply board? Left most board in the second photo.

                          td
                          Must have pushed the wrong key somewhere. 23 volts between N3 and N21 to ground (N6).

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                          • #14
                            Ok here we go I pulled all the voltages for folded schematic upper left quadrant.
                            Ground is N6
                            N3 is 23.08
                            N2 16.16
                            n21 20.91
                            n18 8.73
                            \
                            for the regulated voltages I used N6 but looking closer I may should use n23 I will recheck the voltages there but for now this is what I have using n6
                            n4 16.20
                            n17 9.24
                            n19 14.56
                            n4 16.20

                            Got some bad storms rolling in so it will be tomorrow before I can recheck

                            Thanks,
                            nosaj

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                            • #15
                              n4 15.70
                              n17 8.69
                              n19 14.29
                              n22 2.7

                              So looks like I need a 15v regulator, replace c11 possibly c12 but since I'll have it open also c10.
                              Let me know if you concur

                              Thanks,
                              nosaj

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