Question about BenQ FP731 17" LCD Monitor

1 Answer

BenQ, power is on, screen is almost black, just very dark

Hello
I have a benq, I've read other posts, but I thought with the info of it being very dark, almost black, but can still see a bit, someoen could help me pin point the problem.
Thank you.

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  • 2 more comments 
  • bazaaa Nov 19, 2008

    They said it would cost about $120-$150 to fix.
    I read this in aonther post:

    "Its a problem with the inverter. check the 4 transistors, C5707 near
    the connectors for the backlight. If none are defective, look for the
    PF751 FUSE. It sure to be busted.You can replace that with another 3A
    fuse. Remember, you should only replace the fuse if you are certain
    there are no busted transistors in the inverter board. Otherwise, you
    now have a refurbished Benq Monitor"

    How do I check the transistor, if it's good or bad?
    And how do I know if the fuse is busted? Broken? It looks okay to me.



  • bazaaa Nov 19, 2008

    Okay, thank you very much. That is too difficult for me. I phoned one of very few LCD places here in the city, and they said it would cost about $120-$150 to fix. So it's not even worth it I guess.

  • Anonymous Nov 24, 2008

    Benq, power is on, screen is almost black, just very dark problem. Just looking at a Benq FP731 which my boss had replaced the capacitors on but that did not fix it. He decided to scrap it! I just checked it and found that it read 1Mohm across the fuse for the inverter. Checked the transistors but none found faulty. Replaced the fuse and its working fine. It's now been on for an hour without any problems.

  • DKRASH Jan 27, 2009

    Where can you buy this 3A fuse that that needed to be replaced? Its PF751.
    Also, what is the best way to test the fuse if you are using a digital muiltimeter? Thanks.


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  • 153 Answers

You can not fix this problem from the panel buttons, the problem is something to do with the circuit board. Its the inverter cicuit that has one or couple of components faulty. I susgest you bring it o the repair shop. cheers.

Posted on Nov 19, 2008

  • Trevor Sauna
    Trevor Sauna Nov 19, 2008

    Its complicated if you don't know how to use a multimeter to check and
    understand how transistors are checked using the resistance test. For
    the fuse just use a analog multimeter put knob to X10 and connect the
    two probes to the terminals of the fuse and see if the needle
    points to zero that means fuse is OK if not the fuse is open. for the
    transistors we go step by step.

    Step by step instructions:


    The instructions are given primarily for transistors as these are the most common types in use. The variations
    are shown for PNP (positive, negative,positive)varieties - these are indicated in brackets (.. ..
    ..):




    1. Set the meter to its ohms range - any range should do, but the middle ohms range if several are available is probably best.


    2. Connect the base terminal of the transistor to the terminal marked positive (usually coloured red) on the multimeter


    3. Connect
      the terminal marked negative or common (usually coloured black) to the
      collector and measure the resistance. It should read open circuit
      (there should be a deflection for a PNP transistor).


    4. With
      the terminal marked positive still connected to the base, repeat the
      measurement with the positive terminal connected to the emitter. The
      reading should again read open circuit (the multimeter should deflect
      for a PNP transistor).


    5. Now reverse the connection to
      the base of the transistor, this time connecting the negative or common
      (black) terminal of the analogue test meter to the base of the
      transistor.


    6. Connect the terminal marked positive, first
      to the collector and measure the resistance. Then take it to the
      emitter. In both cases the meter should deflect (indicate open circuit
      for a PNP transistor).


    7. It is next necessary to connect
      the meter negative or common to the collector and meter positive to the
      emitter. Check that the meter reads open circuit. (The meter should
      read open circuit for both NPN and PNP types.


    8. Now
      reverse the connections so that the meter negative or common is
      connected to the emitter and meter positive to the collector. Check
      again that the meter reads open circuit.


    9. If the transistor passes all the tests then it is basically functional and all the junctions are intact.


    If this steps seems difficult to under stand, i would recommand you to
    bring the components to a technician to check it for you. Good luck.

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