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Gulbransen Theatrum model 3318w not firing on bottom keys and upper f sharp

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  • Gulbransen Theatrum model 3318w not firing on bottom keys and upper f sharp

    Hey guys!

    I have a friend who I'm repairing a Gulbrasen Theatrum 3318W home electric organ for.

    The good news:
    He owns an oscilloscope! A rare tool to have up here, but we do have a functional one if need be for testing. Along with a multi-meter, and various other electricians tools. The rotating drum in the back spins well, but doesn't seem to change the noises if it's slowed or increased by switch speed (?) all keys on the upper keyboard but the f sharp fire no problem.
    Bad news:

    The organs not firing on the entire lower keyboard, but the contacts, resistors, and diodes all appear to be in good shape. I've trace the failed F sharp back through the upper keyboard register and the back boards, to the 3rd (leftmost if your facing the back of the organ) and marked it, all the components until there appear to be functional.

    The entire lower keyboard doesn't create sound, I haven't been able to test the diodes or resistors on the connecting board yet.

    In addition the walking waltz circuit blinks a tempo light but doesn't seem to do much more, and the only upper switches (type of instrument) that have any effect are the harpsichord and keyboard organ switches. All others disallow sound when applied and the keyboard/ harpsichord are off.


    Any help in getting this running again would be appreciated, I'll be back soon with pictures and readings, just let me know whats required of me and we can go from there, I do have a very decent amount of electrical experience (high school robotics and electronics, automotive circuits) but some of these ICs seem to be beyond my ability to effectively test without the proper information. Thanks guys!

  • #2
    Do the voices on the preset pistons sound? ie Harp, Marimba, Chimes, Piano, Sforzando.
    Do the Solo and Acc drawbar pistons enable the drawbars?
    With the harpsichord tab down is there any sound from the highest F#?

    Looks like you've found the tone generator board. Left end of the top shelf. The 3318 should have a Top Octave Synthesizer type. It will have one square silver tuning coil on it. Is that what you have?

    td
    Servicing electronic organs since 1969.

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