Treadmill (Profom 770 EKG) runs at full speed then stops

Discussion in 'The Projects Forum' started by ichudov, Aug 13, 2014.

  1. ichudov

    Thread Starter New Member

    Aug 13, 2014
    3
    0
    I have a treadmill Proform 770 EKG. It has a MC60 controller board.

    It powers up fine and boots up.

    If I select any speed, for example 2 MPH, and press START, instead of 2 MPH it runs at full speed.

    Pressing STOP button does not help, it keeps going.

    After a minute or less of running, it used to stop running by itself.

    Now it no longer stops running at all and the treadmill needs to be disconnected with the main power switch.

    Please note that the speed sensor appears to be working correctly throughout, as actual running speed is displayed.

    I spent a while troubleshooting this, looking at speed controller, LWH terminals for the potentiometer input etc and I cannot make up my mind as to what could cause such errant behavior and refusal to stop.

    I am eternally grateful to the gentle folks here who would have some words of wisdom for me. I would like to troubleshoot it and isolate the problem.

    Thank you.
     
    Last edited: Aug 13, 2014
  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,999
    745
    You need a schematic of that PCB, if its going into full speed it will be the pwm motor driver transistor or controller,reverse engineer the motor drive.
     
  3. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,565
    2,379
    The MC-60 uses an SCR bridge with a opto coupler to fire the SCR's, if the opto output is shorted the SCR's are on full.
    Max.
     
  4. ichudov

    Thread Starter New Member

    Aug 13, 2014
    3
    0
    Thank you VERY much guys. Your comment about opto coupler makes a lot of sense. I will try to risk and get a new SCR controller. Thanks
     
  5. ichudov

    Thread Starter New Member

    Aug 13, 2014
    3
    0
    Well, replacing the motor controller with a new one fixed the problem. Thanks for all your helpful suggestions!!!
     
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