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circuit board testing ?

Discussion in 'Troubleshooting and Repair' started by cwb, Apr 18, 2012.

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  1. cwb

    cwb

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    Apr 18, 2012
    Don't know if anyone can help

    I've got a circuit board from a tread mill that appears to be faulty, is it possible to test just the board without the rest of the tread mill as it's so heavy to take anywhere.

    Have tried asking at a couple of local electrical shops but can't seem to get a straight answer (don't think they know).



    Would appriciate any advise
     
  2. davenn

    davenn Moderator

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    Sep 5, 2009
    hi cwb
    welcome to the forums :)

    we would need a bit more info to be able to help.
    do you have any circuit info for the board ?
    how about taking a photo or 2 of it -- nice and sharp
    what are the specific symptoms of the fault ?

    cheers
    Dave
     
  3. selanac

    selanac

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    Apr 15, 2012
    When you say it's faulty, what is it doing or not doing? Does it have power?
     
  4. cwb

    cwb

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    Apr 18, 2012
    I was told it had the problem from new so maybe an assembly fault.

    When treadmill is turned on the console counts down, at the point the belt should turn it trips. I've tried disconecting the motor but the problem still occurs.

    If the motor is turned manualy by walking on the belt, it counts down and only trips when you stop.

    I've done the obvious checks, all connections/joints and wires seem ok, although there appears to be an item missing from the board, marked as TVS1 or maybe TUS1. Don't know if it should be there or not.

    Will post some pics seperate as I keep losing text when trying.
     
    Last edited: Apr 19, 2012
  5. cwb

    cwb

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    Apr 18, 2012
    Couple of pics, not very clear now uploaded, :eek:

    Will get some better ones but you can see where the part appears to be missing.
    It has ac going to the board and motor is dc, also some form of speed controller.

    If all else fails do you think it would be worth changing some of the components, I don't know alot about electronics although I can solder this type of board, but would need help to id what does what.

    Have tried to google some of the numbers but with no luck.
     

    Attached Files:

    Last edited: Apr 19, 2012
  6. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Were those devices at the top right of the first picture connected to a heatsink?

    When you say "trips" what exactly do you mean?

    Does it ever provide power to the motor? Even the briefest kick?

    Does the motor connect to the two spade connectors near the top right of the board (first picture)?

    Can you read off anything written on the three large components on the top right corner of the board?

    Can you show a similar image of the underside of the board.
     
  7. KJ6EAD

    KJ6EAD

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    Aug 13, 2011
    Boards are often intentionally produced with parts "missing", technically referred to as unpopulated component locations so this is not by itself cause for alarm unless there's evidence that it was once there and has been desoldered.

    The designation TVS1 suggests a transient voltage suppressor which would be there either to protect sensitive components from voltage surges on the incoming power line or to protect the control circuitry from the high voltage spikes produced by the motor.

    My first guess would be that the output optocoupler has failed. That's the small white IC near the big capacitor with the label ironically proclaiming the board has been passed by the quality control inspector.
     
    Last edited: Apr 20, 2012
  8. cwb

    cwb

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    Apr 18, 2012
    The three components in top of pic do go to a heatsink and are numbered

    Small one S6025L middle one G80N60 UFD G11 large one B2 MUR3060PT and the motor does connect to the terminals just below them.

    Has it's own trip switch ( as in pic ), the motor makes no attempt to move at all and I'm a bit reluctant to put my meter across it incase that blows before the trip. Do you think it would ?.

    Is the small white ic the square thing with six pins ? 0604 TLP561G

    Much appriciated

    pics to follow
     

    Attached Files:

    Last edited: Apr 20, 2012
  9. KJ6EAD

    KJ6EAD

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    Aug 13, 2011
    Last edited: Apr 20, 2012
  10. KJ6EAD

    KJ6EAD

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    Aug 13, 2011
    I notice you included a photo of a circuit breaker. Is that the part that trips?
     
  11. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    25A 600V SCR

     
  12. cwb

    cwb

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    Apr 18, 2012
    Thanks KJ6EAD, I'll have a read .

    Thats what trips but not straight away, just when the motor should start.

    Should have said earlier that it also has incline, which is driven by another motor, this works fine until you try to start the running mode then it trips.

    Which part of the board controls the speed ?, it has a magnet type sensor on the wheel that drives the belt.
     
  13. KJ6EAD

    KJ6EAD

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    Don't worry about what controls the speed for now. That magnet sensor may just feed the speed/distance on the display. You need to check for shorts like Steve said. I'd start with the IGBT and the rectifier.
     
  14. cwb

    cwb

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    Apr 18, 2012
    Cheers Steve

    I've got a multimeter and have done basic checks on power in and wires, I'll try and see if I'm getting any output to the motor.
    Is there an easy way of testing the CB, I suppose if I bypass it and rely on the consumer unit it could cause more damage.
     
  15. KJ6EAD

    KJ6EAD

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    :confused: There's no point in asking for advice if you intend to ignore it. Maybe you need to refresh the page to see what you've missed.
     
  16. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Measure the resistance between each of the leads of the devices that were attached to the heatsink.

    looking from the front (the side that doesn't touch the heatsink) assume the leads are called 1, 2, and 3.

    measure from 1 to 2, 1 to 3, and 2 to 3.

    Do this on an ohms range and report any that have zero resistance (or less than an ohm anyway)

    Don't try using this without the breaker. You may have fireworks.
     
  17. cwb

    cwb

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    Apr 18, 2012

    I posted before I'd seen that one :eek:

    I'm very greatfull for the help :)
     
  18. KJ6EAD

    KJ6EAD

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    Aug 13, 2011
    Oh, good. I hoped that was the case.
     
  19. cwb

    cwb

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    Apr 18, 2012
    As you look at the pic

    Left one - Resistance between 1&3 only

    Middle one - No resistance on any

    Right one - resistance between 1&3 only
     

    Attached Files:

  20. KJ6EAD

    KJ6EAD

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    Aug 13, 2011
    That's pretty much what I expected. It looks like the IGBT is shorted. Can you test the IGBT and the rectifier with the meter leads reversed or just do it again both ways?

    Your meter doesn't happen to have a diode test feature does it?
     
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