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Discussion in 'Electrical Engineering' started by Den Murray, Mar 4, 2004.

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  1. Den Murray

    Den Murray Guest


    A little education for me please!

    I've got a direct drive record deck (240V/50Hz), if I run it through a
    step-up transformer (120V/240V) on a 120V/60Hz supply what will the effect
    on the motor be? I asusme that the speed will be increased by 20% (i.e. a
    factor of 60/50). Will there be any other effects?

  2. DarkMatter

    DarkMatter Guest

    That would depend on the type of drive motor. Some are tractored by
    the line frequency, and some are DC driven, and tractored by a control
    board. I would say that most are of the second type. Using the line
    freq for something like audio streaming is bad cause we HEAR it.

    What will be off is the line excited neon that will flicker at 120
    Hz, as opposed to 100Hz, making the speed setting ticks along the
    platter edge incorrect for setting the speed. I think there are some
    you can print out, and tape on though that will allow proper setting
    at 60Hz.

    If it is an old cheapy turntable with no speed setting, you would be
    at the mercy of the internal circuits or line frequency, whichever is
    relevant in your case.
  3. steve h

    steve h Guest

    If the deck has a pitch control it is most likely dc or uses a pulse
    generator to drive the motor, few direct drive decks are powered by a
    synchronous mains motor.

    Steve H
  4. sQuick

    sQuick Guest

    I would have to agree with DarkMatter here,
    most drives owned & opened up are DC motors.
    There are usually a couple of pots inside to tweak
    the 45 or 33 1/3 speed.

    so 50hz or 60hz, shouldn't change the rpm, but would
    have an effect on any timing strobes on the deck.

  5. DarkMatter

    DarkMatter Guest

    The problem results when the 60Hz strobe is used on the 50 Hz lands
    on the platter edge for speed control. It results in nearly a 17%
    change in speed, if "used" as if correct. Many platters I am aware of
    had both 50, and 60 Hz lands on them. If not, they are downloadable
    somewhere, I'm sure. They can also be calculated, and a custom
    template be drafted.
  6. DarkMatter

    DarkMatter Guest

    My uncle recorded hundreds of thousands of old 78s onto tape, right
    after buying the new disc usually. His collection is now in the
    historical archives in Cincinnati. They were every type of music,
    IIRC. I was but a kid. I sure wish I had that collection now though.
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