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  1. #1
    B.M.
    Guest

    Default Monitor Problems

    Good Morning all.

    Problem to start the day.

    Sons Monitor has packed a sad.

    Upon power on little green light beside On/Off switch flashes once and then nothing, dead as a dodo!

    The Monitor is a Proview 15 inch but nobody seems to want to take responsibility for the mainboard.

    Now, using my prehistoric technical skills I have located a transistor designated Q601 (which is a C5296) attached to a very large heat-sink which surrounds the flyback transformer.

    Unfortunately, well I think unfortunately, the Emitter Base resistance is 0 ohms forward and reverse.

    So the question is:

    1: Does this sound like the problem?

    2: If so, is something likely to have blown the transistor or are they known to die of natural causes?

    3: Where can I purchase a new one or an equivalent?

    Any ideas or comment would be greatly appreciated.

    Cheers

    Bob


  2. #2
    Mike
    Guest

    Default Re: Monitor Problems

    <waits impatiently for Billy T to reply>

    Mike.

  3. #3
    honeylaser
    Guest

    Default Re: Monitor Problems

    not sure about the technical problems, when one of our monitors dies we don't even bother trying to fix it (unless it was worth heaps).

    as far as a new one goes, use pricespy to find the best deal. its an invaluable resource.

  4. #4
    tweak\'e
    Guest

    Default Re: Monitor Problems

    are you sur the monitor is at fault not the video card?

  5. #5
    godfather
    Guest

    Default Re: Monitor Problems

    C5296 (actually 2SC5296) is (I think) NPN 1500 Volt, 60 Watts. Google may give you an equivalent, perhaps a BUX 80?

    Sounds like the EHT/Horizontal scan driver transistor, but you don't know if it died of old age or because of shorted turns in the transformer or similar.

    You would need to do a transformer test with a flyback tester or any replacement could become a 3 legged fuse (again).

  6. #6
    B.M.
    Guest

    Default Re: Monitor Problems

    Thanks all.

    Yep fairly sure it's a monitor problem tweake. (Another Monitor works fine)

    Had a lot more luck searching for a 2SC5296 as opposed to a C5296 gf.

    However, I note that a 2SC5296 has a built in 50 ohm resistor and Diode which can trick one into thinking there is an Emitter- Base short when in fact there isn't! Hmmmm.

    In case anyone else is interested this isn't a bad site
    http://www.repairfaq.org/sam/deflfaq.htm

  7. #7
    Billy T
    Guest

    Default Re: Monitor Problems

    Hi BM

    Your measurements might also be confused by the driver transformer secondary. Did the main fuse blow? Unless it did it is quite unlikely (though not impossible) that the transistor is short circuit B-E.

    What is more important is whether or not there is a short from the collector to ground.

    If you want to be very brave, connect a 75 watt 230v light bulb from collector to ground (on flying leads) and switch on. If it lights up the power supply is OK and the transistor is not s/c.

    The problem could then be a loss of drive and in that case if you can locate the driver tranformer check for dry joints on the pins. Just a guess!

    Awaiting results :O

    Cheers

    Billy 8-{)

  8. #8
    B.M.
    Guest

    Default Re: Monitor Problems

    Now your talking Billy,

    This is a bit of me, a light bulb indeed, to go with my old Avo 8 and new fangled Dick Smith digital multi-meter.

    Things are pretty basic on this ark. (It's the likely "arc" that's bothering me at the moment)

    I think I was tricked by this type of transistor as the fuse is definitely not blown. (yet!)

    Will let you know if I survive the exercise.

    Cheers

    Bob

  9. #9
    B.M.
    Guest

    Default Re: Monitor Problems

    Ummmmmmmm Billy,

    The light came on for a brief second, then all the lights went out! Whole street in fact!


    Nahhhhh, just joking, light glowed but that's about all, would be scratching to read by it. (10 watt glow maybe).

    However, must prove something?

    I only left it on for about 10 seconds for fear of creating more problems.

    Any point in taking a voltage reading across the bulb?

    Got me interested this one.

    Cheers

    Bob


  10. #10
    godfather
    Guest

    Default Re: Monitor Problems

    Voltage across the bulb is a bit irrelevant, as its a switched wave and certainly wont read correct (what is correct anyway?) on the digital...

    That probably proves the power supply and the transistor. If its the Line Output Transformer......new monitor?

    A lot of the functions derive a signal / supply from the EHT LOPT circuitry <recalls television principles from James Logie Baird's era>

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