Motor speed issue with Portastudio 424 MKI after replacement

Discussion in 'TASCAM DIY Repairs and Mods' started by Trent, Sep 7, 2019.

  1. Trent

    Trent New Member

    Joined:
    Sep 2019
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    Gear:
    Tascam 424 MKI
    Hi,

    I'm having an issue with my 424. When I got it it needed a new motor, the old one was dead and was too weak to move anything or engage the play / record head. I replaced it with a model EG530YD-2BH, since I was unable to find the original model anywhere. This replacement has the exact same specs as far as I can tell; 2000/4000 rpm, CCW, and 12V. The issue is when it's now turned on, the motor will spin at full speed, as if the A and B pins of the motor are open. When the motor is disconnected, the resistance across the A/B wires on the board are around 30K ohms. Additionally, the speed switch does nothing to change the motor speed, though the pitch knob does speed it up or down slightly. The motor seems to be working fine, and if I short the A/B pins the motor will slow down to it's minimum speed. This makes me think that the motor is not the problem, but it is something in the speed control circuitry. If I can supply any additional details I would be happy to.

    Thank you!

    Trent
  2. SkywaveTDR

    SkywaveTDR Active Member

    Joined:
    Feb 2014
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    From:
    Chicago area
    Gear:
    Teac, Tascam, Sony
    I hate to say it but when putting in these third party motors it is not always plug and play and might require a bit of engineering to change circuits to allow them to work. I don't recall doing a 424 Mk II yet but I should keep track of the changes I have done as they are many.
  3. Trent

    Trent New Member

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    Tascam 424 MKI
    So I got the motor working, I ended up taking the original motor apart and replacing one of the IC's in it (AN6605). The original was badly burnt. Now I'm having an issue with the tape head not staying engaged. It engages fully, but will promptly disengage. I think it's something to do with the electromagnetic actuator not staying on. Any ideas as to what could be causing this?
  4. keef

    keef New Member

    Joined:
    Mar 2019
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    Just a guess but could it be the latches in the corner that engage with the tape cassette?