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Gulbransen Power Supply Redux

Discussion in 'General Electronics Discussion' started by roughshawd, Oct 18, 2020.

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  1. roughshawd


    Jul 13, 2020
    I have a burned up transformer from a Gulbransen organ.
    The power supply delivers multiple voltages to the system, but is going to be costy to repair to original. Can I replace the PS with multiple power supplys, one for each of the voltages and bridge them or something?

    Attached Files:

  2. Kabelsalat


    Jul 5, 2011
    Yes, it's possible, but bear in mind you need negative supply voltages as well.

    Also be sure each supply can deliver enough power - i.e. should be able to deliver at least same current as LM317T is capable of. Also you have the issue of getting 70V DC.
  3. bertus

    bertus Moderator

    Nov 8, 2019

    You could replace the transformer with 3 smaller ones:

    gulbran1 comments.jpg
    Assumed the electronics is still fully functional.

  4. AnalogKid


    Jun 10, 2015
    You might have to go with a hybrid solution; buy a +5 / +12 / -12 supply (commonly available as either linear or switching), and recreate the +/-35 V supply with off-the-shelf components. 35 V is a little below the rectified output of a 24 V transformer. What is the +/-35 V for, and is there any way to estimate the tolerance of that part of the instrument for something like +/- 31-33 V?

    If you use what used to be called a "control transformer", these have multiple primary taps. For one with dual 24 V secondaries, using the 110 V primary tap in a 115 V environment will get the output up to 35 Vpeak.

    Note that a 200 W transformer isn't cheap. What would a factory transformer cost, and what is your budget for the project?

    Cannonball likes this.
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