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Pre-Freyette VHT 50CL - Power supply burned up. Need gut shot to repair

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  • Pre-Freyette VHT 50CL - Power supply burned up. Need gut shot to repair

    I got one of these in on my bench last week. It powers up with good B+ but no bias voltage to speak of. The power tubes redplate after a minute of course.
    I've never heard of anyone getting a schematic out of Freyette so I wasn't even going to bother trying.

    From what I can tell, the power supply board had what we will call a "small fire" and some parts in the bias circuit are obviously missing. For example, there is a burn mark on the top of the board where a resistor used to be. Also, someone seems to have done something with a small piece of jumper wire at some point and managed to burn a bunch of wires in the process. It's kind of a mess. Picture of the underside of the board attached for reference.

    Does anyone have one of these who could provide me with a gut-shot of the top and bottom of the power supply board so I can see what's supposed to be populated and connected?

    thanks!
    Dave
    Attached Files
    --------------------
    Dave Randolph
    StarrSound
    Project Studio, Repair Shop, Generally Cool Place
    Corinth, TX

  • #2
    How about making a sketch of what IS there?

    If there is an actual bias tap from the power transformer, there are only so many ways to make that a varying value (if it is adjustable).
    Bias is bias. Vac through a diode, a few resistors & a capacitor.

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