Treadmill goes high speed then blows the fuse

Discussion in 'General Electronics Chat' started by yogi799, Nov 25, 2015.

  1. yogi799

    Thread Starter New Member

    Nov 25, 2015
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    Last time treadmill ran, my son says it was fine, then all of the sudden very high speed and then stopped. We could smell something burnt.

    I take the cover off and find good connections to the MCB, but there is a blown fuse.

    I replaced the fuse, the lights on the MCB turn on when power is plugged in and the electronic displays as well.

    Turn the treadmill to START and the motor goes very fast and within .5 seconds the fuse is blown again.

    Tried the motor on a 12V car battery - works no problem, turns slowly without noises or sparks.

    Also, when I replace the fuse and plug in to power, a yellow LED on the MCB lights up. That LED has "SPEED" printed next to it.

    I am VERY new to treadmills, can you treat me like a 5 year old?

    What is wrong and can I fix/replace anything?

    It is Free Spirit treadmill 302001, I believe. I can upload pictures of the board if needed. Much appreciated.
    (I know there are similar threads to this one, but I wanted to describe my particular case and the treadmill model)
     
  2. yogi799

    Thread Starter New Member

    Nov 25, 2015
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    Here are the pics

    [​IMG]

    [​IMG]

    [​IMG]
     
  3. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Most likely the mosfets have blown, the components on the rear aluminum heat sink.
    Max.
     
  4. yogi799

    Thread Starter New Member

    Nov 25, 2015
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    Thanks Max, can you guide me a bit closer? I see something at the back, but is there a particular part, with a name, that I should look for? Proprietary or generally available? Simple replacement?
     
  5. MaxHeadRoom

    Expert

    Jul 18, 2013
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    You would need to remove the heat sink clamp on the top R.H. side to see the vertically mounted components underneath, they will have a part No. on them.
    Search the part No's at Digikey etc.
    Max.
     
  6. yogi799

    Thread Starter New Member

    Nov 25, 2015
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    OK, thanks a Million Max. Will do so.

    (un)Related question... Say, worst case scenario, I cannot get the part or whatever. Could I make my own speed controller connected directly to the motor and mounted near the controls up on the top, just so the kids can still use it? The motor works fine... if I could just control its speed... Is it safe to do that? What do you think (again, that'd be my plan B).
     
  7. MaxHeadRoom

    Expert

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    You can get controllers such as KB or make your own, the problem is that most have a speed sensor on the motor to control rpm.
    Also the commercial controllers are made so that the speed control has to be at zero before you can increase the speed, this is so someone standing on the T.M. does not have full rpm right away.
    I would take a crack at fixing that one first, do you have a meter etc?
    Max.
     
  8. yogi799

    Thread Starter New Member

    Nov 25, 2015
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    I have access to the multimeter (if this is what you meant).
    Here is the pic again, are we talking about replacing these two transistors?
    [​IMG]
     
  9. MaxHeadRoom

    Expert

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    Yes, I would test them with a meter out of circuit first.
    The fact it powers up OK I don't think it is the DC bridge BRT1, the other reason for it to take off is if it has a optical tach and that is defective.
    Max.
     
  10. yogi799

    Thread Starter New Member

    Nov 25, 2015
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    OK, thanks again Max. Glad to have an expert here. I know you've helped others before with similar issues (I've seen some threads) but each case is a bit different (and diff. equipment). I'd get drunk (and send you a 12-pack) if I could fix it myself. Probably a long shot, but who knows - if I could actually find these transistors online for not too much dough... Maybe...? (I've never done electronic repairs before... I've literally soldered one tiny thing in my entire life. I presume these two transistors need to be cut off with side-cutters and soldered back, eh?)
     
  11. MaxHeadRoom

    Expert

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    You would need to carefully unsolder the existing leads, if you cut them and the device is OK then you replace them unnecessarily.
    Digikey should have the new replacements, what country are you in?
    At 120vac in I assume it is N.A.?
    Max.
     
  12. yogi799

    Thread Starter New Member

    Nov 25, 2015
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    Hey bud. Likely next door to you? GTA. Canada. I'm about to start taking that thing apart...
     
  13. spinnaker

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  14. GopherT

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    Nov 23, 2012
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    Stop!

    I think max nailed it - optical tachometer. Also, look at all the cat hair / dust on the board. It is very possible that the optical tachometer is just dirty and full of cat hair and lint.

    Clean it up with a can of dust off or vacuum cleaner. Then try again.
     
    MaxHeadRoom likes this.
  15. spinnaker

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    Why do need it running anyway? Don't most people just use their treadmill to hang clothes? :)
     
    AnasMalas likes this.
  16. MaxHeadRoom

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    Not quite, I live within sight of the Grey Cup stadium!
    Max.
     
  17. yogi799

    Thread Starter New Member

    Nov 25, 2015
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    Where is the opt tach in my pictures?
     
  18. GopherT

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    There is usually some type of feedback system to control motor speed. Look for some wires going to some type of axle or pulley. Maybe even the back of the motor. Essentially a toothed wheel or perforated disk and an infra red light and detector to detect pulses of light as the motor turns. If the dirt is blocking the sensor, then the motor thinks it is stopped and more current applied (or higher duty cycle). I am not sure where it might be on your treadmill.
     
  19. yogi799

    Thread Starter New Member

    Nov 25, 2015
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    Are we talking about this part (sensor near the wheel?). I don't know about that... the tread goes really fast immediately after I press START... as if it was given the highest power from the get-go. How would I test it?

    [​IMG]

    Also, here is one of the transistors.

    [​IMG]
     
  20. GopherT

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    That is exactly the type of sensor I was talking about. Now, there should be the light source on the other side of that pulley. It looks like that area is full of cat hair. Take off the sensor, clean it out. Make sure the cat hair in the pulley is cleaned out as well - so the sensor' slight is not blocked. Then try to find the second half of the sensor on the other side of that pulley and clean that too.

    Finally, make sure they are well aligned - pointing directly through each other.
     
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