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Conn 652 Problems

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  • Conn 652 Problems


    I am in despair: A few days ago I have bought a Conn 652. The seller said everything is working fine without problems, so I spend much more money than if I had to restore it. Yesterday I tested it and nothing does seem to work properly :'(.
    If I add Tibia to the Great, each Tibia doesn't play on the full manual, only some octaves.
    If I activate Reed, String, Diapason or Vox Humana, they will also play only on the left half manual. They don't sound on the other keys. There are always some Reeds playing even if I don't press any key.
    Any Tuned Percussion gives only a deep hum.
    NO Coupler is working. If they are activated, there is no effect.
    All Pedal Voices (even Reed, String and Diapason) are working fine.
    Where are the problems?

    Thx, Yaeld85
    Last edited by Yaeld85; 05-30-2014, 01:41 PM.

  • #2
    Did it work before it was moved?

    Static Warning... If you live in a dry climate be sure to touch the metal frame before touching anything else inside the organ and never disconnect a plug or pull out a circuit board with the power on.
    What are your electronic capabilities? Soldering, using a voltmeter, etc.

    The Conn 652 is a multiplexed organ which means one little problem can cause many malfunctions.
    In my experience with them the major issue is cracked solder connections on the pins of the circuit boards where the large white plugs are. Everywhere from the power supply to the keyers.
    Sometimes the plug-in circuit boards lose contact and they should be removed and the edge connectors cleaned.
    Then there's the filter capacitors in the power supply which if are original will probably need to be replaced.
    If you can be specific as to what octaves work it would help. Test with only one flute tab then one reed tab and report back.

    Can you find a pdf of the manual anywhere?



    • #3
      The seller said that there was no problem but I don't know if that's truth.
      I am very familiar with electronics (soldering, voltmeter etc.). I can't check all wires and circuit boards because I don't have the schematic circuit diagrams at the moment but I am going to buy them.
      The organ was rebuilt to work with 230V / 16A
      While I was testing which octaves work, there was something really strange: Sometimes all Tibias were working on the 2 lowest octaves and then nothing was working and then only on the middle octaves. If something is working, it is only on a full octave, not like a2-e4.


      • #4
        The keyboards are divided into octaves from C# to C with a separate drive line for each. Lo C has its own drive line. The same drive lines are used for both manuals.
        These lines come from the multiplexer board which has a custom LSI and 3 DIP IC's on it. Conn was good about labeling the inside of the organ for board identification.
        Check the solder connections on that board's sockets.

        The Keying for each note in an octave is separate on each manual. All octaves on one manual share the same keyer data lines.
        So basically: if you have the same dead note on all octaves it's a keyer line. If the same entire octave is dead on both manuals it's the drive line.



        • #5
          Why doesn't work Tibia 16' only on the keys from c1 to f#1 but on the other keys it's fine?
          Should Tibia 5 1/3', 2 2/3', 1 3/5' and 1 1/3' (only one of them activated at one time and no other Tibia activated) sound on all Keys (c1-c6) or just on keys like g1-g5 etc.?


          • #6
            The organ does not generate 16' c1-F#1 so that is normal.
            Celeste is not generated from C1 to C2.
            The mutations (5 1/3 etc.) should play on all keys.

            The Tuned Percussion generator is on the console floor under the Leslie unit.

            There are four multiplexers in this organ so you should check each manual on tibias, reeds, and tuned percussion voices separately.
            The multiplexers are assigned:
            Accomp / pedal
            Solo / great
            Accomp / tuned percussion
            Solo / great/ tuned percussion

            One problem with multiplexed organs is a bit of missing or wrong data is sent down the line and can cause other problems to appear.

            I suggest looking closely at the solder side of the circuit boards, especially where the pins for the large white connectors are soldered.
            That's the first thing I do when I come across a Conn organ. Resoldering them may solve your problems. Only trouble is there are a lot of them.