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Can anyone identify this transistor?

Discussion in 'General Electronics Discussion' started by Spence, Apr 13, 2015.

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  1. Spence

    Spence

    7
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    Apr 13, 2015
    Looking to repair this circuit board that controls my vehicles AC. I've come across this transistor that is BCE and has given me the readings as follows:

    B-C=0
    B-E=.270
    C-E=.270

    C is also where I'm not getting any power on and this is the failed part of the circuit and the volts seem low to me but I'm all a noob to this. I'm looking to replace this transistor. If anyone can identify this or recommend something from maybe RadioShack that'd be very helpful. Thanks! 20150412_212514.jpg 20150412_221722.jpg
     
  2. davenn

    davenn Moderator

    13,766
    1,920
    Sep 5, 2009

    Hi Spence
    welcome :)

    dunno how you were reading those measurements as they stand that are meaningless till we know if they were voltage or something else and between where and where you were taking the measurements and with or without power applied

    You have another serious problem ....
    top pic
    lower left
    there is a circuit track that has fused .... did you see that ? presumably not as you didn't comment

    To test to see if the transistor is faulty, it would have to be removed from the circuit
    I thought the transistor mite have been a 2SA8651 but I cannot see any info on google, so am now not sure what it is

    Dave
     
    Tha fios agaibh likes this.
  3. Spence

    Spence

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    Apr 13, 2015
    Thanks Dave! Those readings were taken without power applied. I was going off YouTube videos and how to test NPN transistors so that's what I came up with. Yes, I'm aware of that area. This happened when it was on the car, my fault, but used a copper wire to join the track again. I'll go ahead and remove the transistor from the circuit and give a test again.
     
  4. Spence

    Spence

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    Apr 13, 2015
    Got the transistor removed from the board. Going across C and E with positive or negative I get no current flow as I believe is right. However, touching +B to -C I get zeros across the board, touching +B to -E I get a open signal, no zeros or a volt reading.
     
  5. BobK

    BobK

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    Jan 5, 2010
    You don't say what kind of reading you are taking. Is this with the diode test range? If so, try the leads the other way as well. A PNP transistor will need the negative lead on the base.

    Bob
     
  6. Spence

    Spence

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    Apr 13, 2015
    Sorry. Yes this is a diode test. I haven't tried the negative lead on the base yet. Going by how it was printed on the transistor, and board, I was testing it as a NPN. I'll try the other way and see what happens. Thanks.
     
  7. Spence

    Spence

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    Apr 13, 2015
    Tried it was definitely NPN. Picked up a TIP31 and tried that, but not getting enough volts through the circuit.
     
  8. Viktory2k1

    Viktory2k1

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    Apr 14, 2015
    I think your problem is elsewhere. Make and model of car please.
     
    Spence likes this.
  9. Colin Mitchell

    Colin Mitchell

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    Aug 31, 2014
    It maybe a PNP transistor
    You need to do my finger test

    Simplest-Tr-Tester.gif
     
    Spence and Arouse1973 like this.
  10. Arouse1973

    Arouse1973 Adam

    5,165
    1,087
    Dec 18, 2013
    Love the pictures. If you do this it is advisable to take ESD precautions so you don't damage the transistor from any ESD events.
    Adam
     
    Spence likes this.
  11. Spence

    Spence

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    1
    Apr 13, 2015
    You were correct. It was the high pressure switch on my ac compressor. It was shorting out to the body of the compressor. Got it all sorted out. Still had to get a replacement ac control unit. I'll tinker with the old one on another day. Thanks for all the help everyone.
     
    davenn likes this.
  12. Spence

    Spence

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    Apr 13, 2015
    I'll definitely refer to this when I do any future tests. Thanks.
     
  13. Viktory2k1

    Viktory2k1

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    Apr 14, 2015
    Even a high pressure switch is rare to go on you unless the compressor was seriously screwed up.
    Did you have to buy a whole compressor with clutch?
     
    Last edited by a moderator: May 12, 2015
  14. HellasTechn

    HellasTechn

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    Apr 14, 2013
    Dear Spence. You need to remove the semiconductor "transistor in your case" in order to obtain a reliable reading with your measurement instrument. In other words just remove it from the PCB and test it alone with a multimeter.

    From the base of the transistor it should give you a reading to the emitter and collector and by reversing polarity of your probe it should not .

    i think this is the datasheet :

    http://documentation.renesas.com/doc/products/transistor/r07ds1065ej0100_pomosfet.pdf
     
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