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Anyone change an optocoupler on an old Mac tuner?

Discussion in 'Tuners' started by jlovda, Mar 16, 2017.

  1. jlovda

    jlovda Things I loved from the 60's and 70's Subscriber

    Messages:
    3,005
    Location:
    NE Ohio
    Has anyone changed the optocoupler (LDR) on the multiplex board of an MR74 or MX113. Any problems to look out for?

    Thnks
     
  2. KentTeffeteller

    KentTeffeteller Gimpus Stereophilus!

    Messages:
    23,223
    Location:
    Athens, TN
    I'd talk to Terry DeWick about that, he's on the Mcintosh forum here on AK. He knows these tuners very well.
     
  3. Punker X

    Punker X AK Subscriber Subscriber

    Messages:
    3,854
    Location:
    Panic in Detroit
    Had to dig this up.. Got this recommendation from Terry years ago.

    Replace the 144-014 opto on the MPX with a VTL5C9, will need 1K in series with the emitting diode and about 180 ohm across it to adjust the sensitivity as to not mute the signal when muting is off.
     

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