TreadMill running flat out !

Discussion in 'Technical Repair' started by liammcl, Aug 26, 2016.

  1. liammcl

    Thread Starter New Member

    Aug 26, 2016
    14
    1
    Hi,
    Newbie here :)

    I've just bought a treadmill, a Reebok I-run ,
    which , as soon as the counter counts down (3 seconds) , the treadmill speeds up to full speed !

    The display shows that the speed buttons are working by going up in increments
    and the start and stop buttons work fine...
    But the speed is constantly, full on !

    There's no speed sensor on the belt pulley,
    [​IMG]

    and here is a closeup of the board..
    [​IMG]
    In the above picture the things behind the blue capacitor, are linear voltage regulators
    L7812CV (12volts , 1.5 amps)
    and a L7808CV (8 volts, 1.5amps)


    *** There's lots more pictures, from all angles, showing the components, at
    *** http://s103.photobucket.com/user/liammcl_2006/library/TreadMill?sort=3&page=1
    ***

    and the NTC-3D-20 thermistor, gets really hot, within a few seconds.

    [​IMG]

    (please ignore the yellow, orange, red , black wires...
    I had a spare bridge rectifier,so I replaced the original KBPC1510 ..It made no difference)

    Could it be these shorting out? (there is a heat-sink attached to them,[​IMG] normally)


    Does anyone know what's in the big black box?
    [​IMG]

    and here is the reverse side..
    [​IMG]

    I'm a kinda newbie to electronics... but I'm reading up , as we go...

    Any pointers would be gratefully received..

    All the best
    Liam
     
  2. Sabouras

    New Member

    Aug 27, 2015
    6
    1
    Dear Liam,
    The black box has the PWM controller which drives all the power component PCB includes. This box take the user preference and accordingly made the motor driving. The problem you describe is in the black box.
    It could replaced only from the manufacture.
     
    liammcl likes this.
  3. liammcl

    Thread Starter New Member

    Aug 26, 2016
    14
    1
    Many thanks Sabouras , that make sense...
    I wonder if I can do a work around... rough and ready...
     
  4. Sabouras

    New Member

    Aug 27, 2015
    6
    1
    It is dangerous to do that, but you could try form an arduino or some generator to test which pwm need the power element to driven so you have some constant speed, and then find out how to trim that speed.
     
  5. liammcl

    Thread Starter New Member

    Aug 26, 2016
    14
    1
    wondering if I can use a 10 turn pot etc ...it only has to be rough and ready !


    . I tried 2 car batteries in series, straight to the motor, and it ran fine, if a little slow.

    Then I disconnected the batteries, and ran on the treadmill and noted the voltage and amps output...
    40-50volts DC would do , and about 3 amps...about 4mph.

    I have 4 car batteries lying around... I may give em a go...

    don't want to spend too much at all..

    maybe a step down 240v to 110v transformer with a bridge rectifier would do...
    (or I could wind a transfromer , with taps off , at different voltages...then convert to dc)

    I dunno if a 240v box standard dimmer would do... and then thru a bridge rectifier..

    Just generating ideas atm...I'll look into them a bit more tomorrow

    any other ideas, would be welcome ....

    simple ideas, would be good for me :)

    Cheers
    Liam
     
  6. Sabouras

    New Member

    Aug 27, 2015
    6
    1
    Dear liam,
    If i see see well form the photos the big Mosfet IRFP460 is that which driving the motor. So you could power up your treadmill and then which some small voltage try to connect the + into the pin which is above the black box and then the - in the black wire. With this connection you give up the command to open the mosfet and if all the other working right you must see the motor to speed up.
    After that just trim the voltage into what level you want and permentally will run at a constant speed.
     
  7. liammcl

    Thread Starter New Member

    Aug 26, 2016
    14
    1
    yes, thank you., .I understand.

    I will try and test existing IRFP460C too , just incase it is faulty.
    I don't know how, atm.. but I will google it tomorrow.
    Thanks & goodnight
    Liam
     
  8. liammcl

    Thread Starter New Member

    Aug 26, 2016
    14
    1
    Well, I unsoldered the left one, of the mofset, thinking it was the gate...to see if it would make it the belt stop
    Turned it on, and there was a flash.
    ..so it looks like the treadmill has gone over the rainbow bridge in the sky.:)

    Hang on ! there's a spark of life !
    It only blew the fuse !

    Next up , I'm going to put a resistor in series to the leg of the gate (the left one)


    Cheers
    Liam
     
    Last edited: Aug 27, 2016
  9. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    8,733
    759
    Do not Power with Gate disconnected.

    Check the MOSFET for shorts
     
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  10. liammcl

    Thread Starter New Member

    Aug 26, 2016
    14
    1
    scrap that, about the resisitor...
    I'll try a 240v light bulb in series

    If I had a dimmer switch, I'd use taht ..

    It'll end in tears ;)
     
  11. liammcl

    Thread Starter New Member

    Aug 26, 2016
    14
    1
    Many Thanks..
    I don't know how to do that...atm
    I'll google it , in a mo'
     
  12. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    8,733
    759
    You will need a DMM
     
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  13. liammcl

    Thread Starter New Member

    Aug 26, 2016
    14
    1
    ok, multimeter set to 200 ohms

    pin 1 is to the left... the gate, I think

    between pin 1 and 2 ....2.3 ohms
    between pin 1 and 3 .....2.3 ohms
    between pin 2 and 3 ....0.4 ohms

    ooh ! that looks like a short between 2 and 3 !


    Thanks
    Liam
     
    Last edited: Aug 27, 2016
  14. liammcl

    Thread Starter New Member

    Aug 26, 2016
    14
    1
    just to clarify, I set the dmm to diode testing , and red probe on pin 2 and black probe on 3 , gave 0 ,
    ie a short...

    I have an old computer psu, I may try and get one of that to test..

    cheers
    Liam
     
  15. liammcl

    Thread Starter New Member

    Aug 26, 2016
    14
    1
    Many Thanks R!f@@ ... you have been a great help...thank you !
    I am going to get this as a replacement £3 , 500v, 20amp n-channel mosfet
    http://alturl.com/4kk9y

    I would've liked to have picked one up, but can't get one today..

    Let's see if it does the trick !

    Cheers
    Liam
     
  16. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    8,733
    759
    MOSFET is short. Need to replace that.
    Check the diode next to MOSFET too, for shorts.

    Remove MOSFET and DIODE.
    Install the board and power up. Check if the Tread operates normally. Motor should not rotate but the display should work fine and might generate an error on the display without MOSFET. If error came it is because of no motor RPM
     
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  17. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    Since you blew the fuse, it is advisable to check the bridge for a shorted diode too. But after replacing the fuse, and if it does not blow, Bridge is fine I believe.
     
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  18. liammcl

    Thread Starter New Member

    Aug 26, 2016
    14
    1

    Thanks,
    I have removed the diode too, to check..
    (this is a picture before removal)
    [​IMG]


    With the multimeter set to diode setting,
    and the black probe to leg 1 and the red probe to leg 2 ...the dmm reads 450
    reversing the probles, and it's infinity...
    is the diode ok?

    Cheers
    Liam
     
  19. liammcl

    Thread Starter New Member

    Aug 26, 2016
    14
    1
    All is ok , thanks
    the display powered up fine,
    no movement of the belt,
    and no *bang* of the fuse :)

    I shall order the mosfet from fleabay and hope for the best.
    Many , many thanks, for all your help!,
    it is very appreciated , and thanks for all the time you have spent helping me.

    All the best
    Liam
     
  20. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    8,733
    759
    Diode is OK.
    Check the new MOSFET before soldering.
     
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