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Monitor keeps going into standby mode

Discussion in 'Electronic Repair' started by gavspav, Oct 31, 2006.

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  1. gavspav

    gavspav Guest

    I am having problems with my R15T600 Openframe Touchscreen Monitor.

    After warming up the monitor goes into standby mode for 30 seconds or
    so every few minutes.

    Before going into standby there is a high pitched noise - I can't
    remember if the monitor made this noise before failing or not. When I
    press the touchscreen the frequency of this noise changes.

    I have tested the pc with another monitor and it worked fine. Also
    tested monitor with another pc and same problem occurred.

    Taken the unit apart and i can't see any obvious burnt out bits.

    Anyone got any ideas?

    Thanks,

    Gavin
     
  2. default

    default Guest

    Broken wire at the connector or strain relief? Lose horizontal sync
    and it might do that.

    see
    http://www.networktechinc.com/technote.html
     
  3. Jim Yanik

    Jim Yanik Guest

    Bad electrolytic caps in monitor power supply?
    Look for discolored or bulging caps.
    An ESR meter would be helpful here.Or just swap out all the
    electrolytics.(use low-ESR 105 degF switcher-grade caps)

    How old is the unit?
     
  4. gavspav

    gavspav Guest

    Thanks for the responses.

    I have checked the external power supply and it is fine.

    Can't see any broken wires.

    Don't know how old the unit is as it was bought off ebay a few months
    ago. Looked new when i got it though.

    I do get alot of mad flickering sometimes before it goes into standby.

    Thanks,

    Gavin
     
  5. James Sweet

    James Sweet Guest


    Probably cracked solder joints, shouldn't be too hard to fix but if
    you're not experienced working on electronics you probably don't have
    much chance of fixing it yourself.
     
  6. default

    default Guest

    You sorta hafta look at the horizontal with a scope. There's an
    internal horizontal oscillator. It cooks along well below the real
    horizontal signal frequency wise. The Hsync signal from the computer
    comes along and triggers a new horizontal refresh line before the
    internal oscillator would on its own.

    Lose the horizontal sync, and the monitor's internal oscillator runs
    for a bit but at a lower frequency (that you hear), the big brother
    circuit kicks in and says go to standby we ain't got the right drive
    signals.

    Doesn't have to be a wire - but that's a place to start.

    Any circuit board connection to the Horz or Vert sync signal
    amplifiers could cause similar symptoms.

    Many monitors use single integrated circuits for each - the horz and
    vertical drivers. Both are usually high power devices. They are
    mounted to heatsinks. A common problem is the heatsink expands with
    the warm-up and stresses the leads to the device - eventually breaking
    the solder joint. Both heatsink and IC are mounted to the board - but
    expand at different rates with temperature. Re solder all the
    connections to those parts will sometimes fix that problem.

    It is unlikely that anyone reading about it will give you the right
    answer - you are in the driver's seat and have to think it through.

    I've fixed a lot of monitors and both the vertical and horizontal
    driver circuits fail frequently. (the monitor I'm using now has had
    both problems). Power circuits are another weak link - increase the
    60-50 HZ ripple on a monitor PS and it starts modulating the 60-70 HZ
    free running vertical oscillator.

    Nine times out of nine it is the construction technique and design
    that cause problems - very seldom a part failure (except
    electrolytic's in the PS). They "wave solder" the boards in mass
    production - but not all connections are happy with just a taste of
    solder. The larger leads and problem areas need more heat for a good
    solder joint.

    Then we have the old ViewSonic monitors . . . they hang ten pounds of
    tweaking hardware (coils and pots for pincushion gun drive etc.) on
    the connector to the CRT - they all die prematurely

    Very few component failures for me - but lots of bad solder joints.

    If you could describe the sound better - that might be a clue.
     
  7. David Naylor

    David Naylor Guest

    sounds like and inverter board problem to me, caps changing value is
    quite common sucking down the power supply
     
  8. gavspav

    gavspav Guest

    I've a hunch you are right about the inverter board but basically am
    well out of my depth.

    I took the monitor to the shop yesterday and paid them 30 quid to tell
    me what was wrong with it and how much it would cost to fix it.

    Thanks for all your help but I'm afraid I had to admit defeat!

    Gavin
     
  9. Jim Yanik

    Jim Yanik Guest

    It's a wise man who acknowledges his limitations.
     
  10. default

    default Guest

    Dirty Harry
     
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