this transistor is driving me nuts.

Discussion in 'The Projects Forum' started by jjrford, Sep 4, 2013.

  1. jjrford

    Thread Starter New Member

    Sep 4, 2013
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    I have two (Fuji 974222 NPN) transistors on this forklift. I can't find much out on these ( somewhere I seen they could be 50 amp). I have used the diode check and the ohm scale on my meter. I have used the standard diode check and tried to ohm them out but they have me stuck. On the diode scale the meter will not stabilize and the ohm's is reading wierd.
    I need help trying to figure if they are bad.

    Thanks jjr
     
  2. gerty

    AAC Fanatic!

    Aug 30, 2007
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    Are you checking them in, or out of the circuit?
    Not stabilizing sounds like you may have a capacitor somewhere in the circuit.
     
  3. MaxHeadRoom

    Expert

    Jul 18, 2013
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    A number such as that could be a in house No.?
    Many of the Fuji power semi's are screw terminal connection, is this so in this case?
    Max.
     
  4. shortbus

    AAC Fanatic!

    Sep 30, 2009
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  5. jjrford

    Thread Starter New Member

    Sep 4, 2013
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    Yes it is a cat forklift and checking it on bench. They do have screw terminals. It has a npn diagram on the side of it. How do you check a IGBT module ?
     
  6. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    The NPN symbol does look similar to the IGBT symbol. But if you look closer the is another 'line' drawn under the base of the npn symbol making it an IGBT. Simplified an IGBT is a npn transistor with a MOS gate added to it.

    IGBT modules are pretty robust, so you might have problems in the control circuits. Or even the wiring.

    Here's a PDF on a test procedure for IGBT's and the symbols for a IGBT and NPN so you can see the differences.
     
  7. jjrford

    Thread Starter New Member

    Sep 4, 2013
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    Shortbus I looked at the test procedure but it doesn't look like mine. I took a picture of it and of the diagram. They didn't teach me this in college but I'm learning now. I did more testing and found out if I moved the biggest tab real slow it would make the meter go wild with different readings and at one point I could get an open circuit. So I think I found the problem. Now I need to find a new one that doesn't cost a lot any ideas?

    Thanks for all the help jjr


    View attachment 59118

    View attachment 59119
     
  8. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    Sorry but your pictures don't work. To upload to the forum, under the 'quick reply' box it says "go advanced". Click that and it takes you to another page, on that page there's another bigger box called "additional options". Click on "manage attachments" in the attach files box, and then you can add stuff from your computer.

    Yeah, if you can wiggle the terminals in the module that is a bad thing. Your #974222, is probably a cat number for a fuji part. Did you try these guy's?
    http://www.allindustries.co/eng,material_handling,caterpillar_forklifts,974222.html
     
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