Motor Control Board Repair

Discussion in 'The Projects Forum' started by mkflyfish, Sep 6, 2011.

  1. mkflyfish

    Thread Starter New Member

    Sep 6, 2011
    3
    0
    I have the a treadmill with a bad motor control board. The 3.0 hp DC Motor does not run, but will run from battery. The board is common, and can be purchased for about $200.00

    I'm decent at soldering, and think I could replace a defective resistor, or the part as shown in the photo, though I'm not sure what it is, or where to buy one.

    The photos are attached, top, top closeups, bottom, and bottom closeup.

    I believe the defective part is likely defective because you can see the blackened marks on the connector, and solder being melted away from connection. Could I be so lucky, that I just need to re-solder the part onto the board, that the part itself is internally OK ?

    The part is marked DEC KBJ25J, and has 4 connectors, one of which is black and little or no solder left on it.

    Thank you for your help.

    Michael
     
  2. wayneh

    Expert

    Sep 9, 2010
    12,154
    3,060
    You might get lucky. That looks like a rectifier that has blown a diode. Just Google those numbers. It would be worth the effort, IMO, to try replacing it. It will either blow again, because it wasn't the root cause of the problem, just the victim, or it'll be all better.
     
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  3. mkflyfish

    Thread Starter New Member

    Sep 6, 2011
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    Thank you so much! It is a rectifier! I had been searching with the numbers, but once I added "rectifier" to my search I could actually find it.

    I was able to find a data sheet on it;
    http://www.datasheetdir.com/DEC-KBJ25B+Bridge-Rectifiers

    and a replacement;
    http://ssidev3.specialtysystems.com/nte%5CNTExRefSemiProd.nsf/$$Search?CreateDocument&Query=kbj25b*

    Some of the NTE distributors even have it in stock, for $4. Keeping my fingers crossed.

    I'll let you know how things turn out.

    Michael
     
  4. jwilk13

    Member

    Jun 15, 2011
    228
    12
    Yep, it's a bridge rectifier. The datasheet can be found here. It might be a tough part to find though. You might take a look at this as a replacement, but don't hold me liable if something else blows up :p
     
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  5. praondevou

    AAC Fanatic!

    Jul 9, 2011
    2,936
    488
    It may not be defective. I would first verify the diodes, to do this you may have to desolder it. There should be no short between any of the pins and you can check the diodes with a simple diode tester of your multimeter.

    A bad solder joint can overheat over time, the current is too high for the solder that makes the electrical connection, causing eventually what your picture is showing.
     
  6. SgtWookie

    Expert

    Jul 17, 2007
    22,182
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    The J suffix part is rated for 600v.

    If you are going to use an NTE part, then use NTE5392 which is also rated for 600v
    NTE5393 and NTE5394 can also be used; they have a higher voltage rating.
     
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  7. mkflyfish

    Thread Starter New Member

    Sep 6, 2011
    3
    0
    The project turned out a success! I used the nte5392. Everything appears to be working fine.

    Thank you all for your help!

    Michael
     
  8. wayneh

    Expert

    Sep 9, 2010
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    Ah, the sweet smell of victory, nothing like it. ;)
     
  9. SgtWookie

    Expert

    Jul 17, 2007
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    I took another look at that 1st photo attachment - is the large black cap with the "Q.C. OK" sticker bulging upwards on top? It looks like it might be. If so, you need to replace it. Replacing it anyway as preventative maintenance would be a good idea.
     
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