464 tape speed fluctuates uncontrollably

Discussion in 'TASCAM DIY Repairs and Mods' started by mikewolfe, Dec 4, 2020.

  1. mikewolfe

    mikewolfe New Member

    Joined:
    Dec 2020
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    Gear:
    464 Mk1, M-320b
    Hey all,

    Sometime ago I was gifted a defunct grey-era 464 from my professor. After cleaning the solidified lubricant on the plastic gears the machine worked *near* perfectly. By that I mean, it passes sound, records to tape, and works as you'd expect a 4-track to work.

    My problem is, it seems there may be a problem with a motor or a belt because I'll get very intense pitch dive bombs, as if I abruptly sent the vari-speed from max speed to min. Normally, I'd say this is a fun and cool quirk to working with a cassette machine but it's proven to make overdubbing near impossible.

    Has anyone ever encountered a similar problem with their portastudio and has any advice for how to proceed?

    **PS the belts were all replaced prior to it being given to me and are seated (to my knowledge) correctly.
  2. mikewolfe

    mikewolfe New Member

    Joined:
    Dec 2020
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    Gear:
    464 Mk1, M-320b
    For reference, this was a track I sent through the Tascam and you can hear the effects It has on a full mix being passed through it.
  3. SkywaveTDR

    SkywaveTDR Well-Known Member

    Joined:
    Feb 2014
    Messages:
    622
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    From:
    Chicago area
    Gear:
    Teac, Tascam, Sony
    It sounds like the wrong speed the whole time. Could be a bad pitch control pot or a bad motor. It can only be fixed by experienced Technician as some third part motors require a mod of the circuits to make them work correctly. There are no install and calibrate motors anymore.