Working on treadmill, What will a Bad Capacitor do?

Discussion in 'The Projects Forum' started by Noneleft, May 11, 2014.

  1. Noneleft

    Thread Starter New Member

    May 11, 2014
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    Ok, should start off by saying I have a VERY basic knowledge of electronics. I know most of the basic components and what they do but how everything works together start flying over my head in a hurry. I am motivated and love to learn though.

    So I just got a treadmill that has been sitting for a few years, worked great before it stored and was hardly used even then.

    After quite a bit of messing around with it and getting squat out of the motor, I took the plastic cover off the motor and control board. I noticed a few things right away.

    1: There was a lot of dirt and junk on the board which I promptly blew off with compressed air.

    2: The big capacitor looks like it was leaking and got real hot at one point. Along with possibly the things sandwiched between the heatsinks.

    So I plugged it back in and tried turning it on. Well now things start getting strange. As soon as I turn the machine on (NOT starting the treadmill, just hitting the power button) the motor starts turning. It will not stop or slow down/speed up no matter what is done on the control panel.

    The diagnostic test also gets zero response out of it, it just keeps spinning.

    Now I know it was a bad idea but in frustration I wanted to see if the capacitor was getting hot (it wasn't) or anything so I tapped it and got a low level shock, like half a wall outlet. Pretty sure thats not supposed to happen.

    So I am pretty much positive the cap is bad but would that alone cause these kind of issues? Anything else stand out in the pictures?

    Most importantly, is it worth trying to fix this? It is a nice treadmill and would really like to get it working but no way I can afford to pay someone to do it or buy another control board.

    Here are the pictures:

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    Thanks for any advice!
     
  2. MrChips

    Moderator

    Oct 2, 2009
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    The cream white stuff under the capacitor could be glue applied during manufacturing.

    If the capacitor gets hot, try replacing it, preferably with one with a higher voltage rating that what is written on the current one.

    Try 1500μF/300V if it fits physically.
     
  3. MaxHeadRoom

    Expert

    Jul 18, 2013
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    It looks like the board has been exposed to some contamination over time, there appears to be some material between the pins of the IC's, if this was deposited with any moisture it is not good.
    If you tapped the metallic top of the cap, it is reasonable that you received a shock, these T.M. controllers are not isolated from the mains AC.
    It is possible that one of the driving transistors or Mosfets are turned on, either by a defective component or one that has been shorted by the deposits.
    Max.
     
  4. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    It might also help to clean the circuit board thoroughly. There's evidence of gunge still there, which could be causing shorts or low resistance paths between circuit tracks and component pins/legs.

    Edit: Ah, I see Max had much the same concerns at the same time as me.
     
  5. Noneleft

    Thread Starter New Member

    May 11, 2014
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    The picture doesn't show it real well but the plastic coating on the cap was melted on one side. Is that not a big deal?

    It also looks like there might be small holes melted into the things on the heatsink?

    Indeed there was a lot of junk in there, it was in a basement so moisture is a possibility for sure.

    I guess a cleaning is in order to start out with before going deeper.

    I thought about cleaning the board but didn't know what I should clean it with besides compressed air. Alcohol?

    Thanks for the help!
     
  6. MaxHeadRoom

    Expert

    Jul 18, 2013
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    You can get aerosol cans of board alcohol cleaner that leaves no deposit.
    If the cap is swollen or has discoloured outer and /or the large semi's bolted to the H.S. then these are a prime reason.
    The semi's could be SCR's, Mosfet, or least likely, IGBT's, they should have a number on them.
    It has to be cleaned before any repair.
    Max.
     
  7. Noneleft

    Thread Starter New Member

    May 11, 2014
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    The cap doesn't appear to be swollen or discolored, just the melted plastic.

    I will clean it real good and report back.
     
  8. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    Not a good sign. Possibly blown semiconductors. Can you get a clearer pic of that damage?
     
  9. Noneleft

    Thread Starter New Member

    May 11, 2014
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    Here are some pictures post cleaning. I reinstalled it after cleaning and now it is back to not doing anything.

    Although when I was blowing out the area under the board where another board that deals with the power for the machine sits, I found a fuse rattling around in there.

    Can not figure out where it goes, no place for it that I can see and all the fuse spots are filled. Looks just like the white fuse on the main board. Maybe they just put an extra in there in case?

    [​IMG]
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    If you notice in this picture, the only thing that stood out on the board to me is that area by the relays where the circuit is exposed. Doesn't look to go all the way across the wire though.
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  10. MaxHeadRoom

    Expert

    Jul 18, 2013
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    You really need a schematic to do any logical trouble shooting, that appears to be holes blown in the semi's clamped to the H.S.?
    If you unscrew the H.S. clamp bar, you may be able to read the value.
    Also the trace that looks burnt may have been from one of the suppressors that took a hit.
    Looks like the same make as mine.
    Max.
     
  11. Noneleft

    Thread Starter New Member

    May 11, 2014
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    I am going to call the manufacture tomorrow to see about getting a schematic along with seeing if they are any help.

    Yes, those do appear to be holes in the semi's. If they are from the semi's or from external causes I have no idea. Is that common to happen if they fail? Would they cause the issues I am seeing?
     
  12. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Its possible that if the semi's shorted internally they will blow a hole in the case.
    This can be from a variety of causes and it may be the associated components could be damaged so if they are replaced without further checking, you can damage the replacements.
    Max.
     
  13. Noneleft

    Thread Starter New Member

    May 11, 2014
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    So it is sounding a bit like it may be a lost cause to try to fix this? Just run around in circles only to end up poorer.

    Are there any repair places that would have the skills needed to check something like this out? TV repair shop for example?
     
  14. MaxHeadRoom

    Expert

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    The problem with taking it to somewhere that does not have the documentary resources or experience with the item, it may end up costing more that sourcing a board off of ebay etc.
    If your trouble shooting skills are limited, it could end up being a costly fix.
    Max.
     
  15. Noneleft

    Thread Starter New Member

    May 11, 2014
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    Thats what I am kinda seeing. My skills are about maxed out at this point, like I said, VERY basic.

    New boards are $250 on ebay, way more then I am gonna spend so looks like it may just be time to cut my losses.

    Will try calling the manufacture but not holding out a lot of hope on that.

    Oh well, thanks for all the help, at least I know I gave it my best!
     
  16. MaxHeadRoom

    Expert

    Jul 18, 2013
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    If you want to tinker and have a meter, you could remove the semi's on the H.S. that appear blown and do a resistance check etc, replacements may be as low as $1.50 ea, depending, O.A. the loss may not be great if it does not work out.
    Max.
     
  17. Noneleft

    Thread Starter New Member

    May 11, 2014
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    How would you do a resistance check?
     
  18. MaxHeadRoom

    Expert

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    Preferably desolder/remove the semi's altogether and use a ohm meter for any dead shorts in both directions between pins, and also identify the type of part from any numbers.
    Max.
     
  19. Noneleft

    Thread Starter New Member

    May 11, 2014
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    My solder skills suck, I generally melt the board when trying things like this lol. Can it be done with them still attached?
     
  20. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Yes, but not always conclusive if there are other components, defective or otherwise that are connected that can cause a false reading.
    Max.
     
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