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NEC multisync LCD 1810

Discussion in 'Electronic Repair' started by Dave Walker, May 5, 2004.

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  1. Dave Walker

    Dave Walker Guest

    Hi,
    I now have 3 of these 18 inch LCD flat screens, each one has failed with the
    same fault, after approx 3 years use.
    The monitor turns on, displays a picture for approx half a second then goes
    blank, power light remains on. If the input switch (BNC / D-SUB ) is cycled
    then the picture will appear again, briefly, as will cycling the power too.
    The power lamp remains on after the picture has disappeared. I have tried
    exchanging the external PSU with a good one to no effect.
    If anyone has experience of these monitors, or similar fault, please help!
     
  2. John

    John Guest

    Sounds like the florescent tube inverter or the tube itself may be at fault.
    First test any electrolytic capacitors on the inverter board.
    Good luck John.
     
  3. JW

    JW Guest

    I fixed one of these with the exact same fault several weeks ago - you
    have one or more blown picofuses on the inverter board - IIRC there are
    four of them F2 F3 F4 and F5 - use a ohm meter to find and replace the
    open ones. I suspect that they are slightly under rated at 1.25A, and open
    pretty easily. I replaced 2 of them with 1.5A devices and it's worked fine
    ever since.

    Good luck! BTW, if you ever need a power supply look no further than here:
    http://www.mpja.com/directview.asp?product=15349+PS
    15 bucks! There's a guy who sells them on Ebay for the outrageous price of
    $80.
     
  4. Dave Walker

    Dave Walker Guest


    Thankyou so much.
    I'd looked around inside but I would never have spotted those *tiny* fuses.
    I tested one of the boards, and two were indeed o/c. Even my weller station
    is not good enough to replace them, but in true Heath Robinson fashion I
    extended the connections out with wire to two normal glass 1.6A fast fuses.
    That display seems OK now, it ran for 20 minutes with no problem. Would you
    say it was a new lease of life or short term? Is it the ageing of the tubes
    that causes the failure?
    I'll get round to checking the other two displays soon, but once again,
    thankyou for your help.
     
  5. JW

    JW Guest

    I can't say for sure in your case, but mine has worked fine for several
    weeks now. Like I said, I think that the fuses are a little bit
    under-rated which could have caused the original failure. I had a second
    one with the same exact failure, but after replacing the blown fuses,
    while the screen stayed lit, there are lines through the display, so I'm
    keeping this one for spare parts.
    You're very welcome - I'll bet good money that you'll find the same exact
    fault in the other two; I'm guessing that part of the inverter circuit
    somehow senses the non-functioning parts of the inverter, and shuts down
    as a sort of fail-safe protection. Let me know how you make out with the
    other two, I'm quite curious...
     
  6. Dave Walker

    Dave Walker Guest

    Number 2 - once again two fuses, F4 F5 blown. Replaced them but this time it
    just blinks on / off, continuous cycling, both picture and on / off LED.
    Took apart for another look, F2 blown now. Replaced that, no change.
    Re-checked, all fuses still OK.
    One more to look at, will let you know on that one later.
     
  7. JW

    JW Guest

    Excellent. Say, do any of your displays have a mechanical problem? Mine
    has a problem where the tilt mechanism does not hold the monitor where
    it's positioned. Instead, the LCD display slowly tilts downward till it's
    at it's lowest point. There's a compression type mechanism that seems to
    work using a spring type bushing which causes friction on a steel plate -
    obviously there's not enough friction. However, there is no way to adjust
    the pressure that I can see, and the thing seems to be permanently pressed
    together. The mechanism on my spare is missing. Have you seen this
    problem?
     
  8. Dave Walker

    Dave Walker Guest

    Excellent. Say, do any of your displays have a mechanical problem? Mine
    Final display - once again failed fuses, but the board only ran for minutes
    before strange things occurred, picture appears to smear and collapse. Not
    believing it to be the board at fault I put in a previous display and the
    same problem. Anyway, one out of three is still a success.
    I only have two stands, and both work fine. However, I don't think either of
    them ever saw much service.
     
  9. rtanderson

    rtanderson Guest

    The inverter board that runs the floursecent board, I have seen blows
    those pico fuses too and is usually caused by shorted surface mount
    transistors, so i recommend checking those too nearby those fuses.

    as far as the fuses i have taken a glass fuse of the same current
    rating ..broken the glass and just tack soldered the wire over the
    body of the fuse...being it is the same current rating to open it will
    still protect the circuit.. (heeheehee)

    only thing I hate about these displays is if you leave an image on
    them for extended time the tend to ghost
     
  10. AndyF

    AndyF Guest

    I have just bought an NEC 1810 which has a fault. It displays green
    vertical lines across the whole screen at a regular 1/4 inch spacing.
    The lines are there at power up and when fed from with a PC signal,
    although the picture behind the lines looks fine! Any ideas what's
    causing the lines?

    Andy
     
  11. Michael

    Michael Guest

    Your LCD is bad. Specifically, the driver ICs that address each row and
    column have failed, or the bond between the conductive glass and the
    metal conductors, at the edge of the screen, has failed. Given that you
    have lines recurring at regular intervals, as opposed to one or two
    random ones, I'd guess it's the ICs. There's nothing you can do to fix
    that, I'm afraid.

    I've seen this on many laptop LCDs and a few of the type used in pocket
    TVs and Video Walkmans. It was a very common failure in the earlier days
    of LCDs, but it still happens.

    Sincerely,
    Michael
     
  12. hrijswijk

    hrijswijk Guest

    Hi,

    Have you found the solution for the monitor which "ran for minutes
    before strange things occurred, picture appears to smear and collapse".

    I've a monitor NEC LCD1810X whit the same problem.

    Harm
     
  13. Dave Walker

    Dave Walker Guest



    Afraid not - I substituted the LCD panel with all the attached boards, no
    change - so it looks like again the inverter board.
     
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