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monitor shutdown

Discussion in 'Electronic Repair' started by yhan, Sep 3, 2007.

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  1. yhan

    yhan Guest

    hi there again!

    I am repairing an old monitor (I was not able to get the serial). But
    its oldy im sure. During power on, i feel a static at the front of the
    monitor. An indication of a high voltage but after a few minutes, 4
    minutes i think, it suddenly shutdown. So I used my multimeter and
    tested the collector of HOT. I measured a voltage but when the monitor
    dies up, the voltage also disappears. I changed some bulging
    capacitors but still the problem persists.I suspect the deflection
    yoke but I have no yoke tester. I heard that running a monitor without
    deflection yoke disconnected is not good. I am a little bit lost here
    because I havent practiced it for long time now. So can anybody give
    me suggestions on how to fix this problem. I know safety precautions
    in electronics. I want friendly advise please. Thanks in advance.
     
  2. Jerry G.

    Jerry G. Guest

    I would doubt the deflection yoke to be bad.

    Use an ESR meter, and check all the caps in the scan and power supply
    sections. It is impossible to tell visually if a cap is electrically bad,
    unless it had physical damage.

    A common cause of a start-up, and shut down, is that there is a fault in the
    high voltage regulator, any part of the power supply, or there is a scan
    failure due to failed components.

    The only way you will be able to fix this monitor is with proper
    troubleshooting. This would take a good knowledge of electronics, experience
    in monitor servicing, and the proper tools to do the work.

    I would suggest you give the monitor out for an estimate. This way, you can
    make an intelligent decision to know if it is worth to service, or simply
    replace it. Also, when working in TV monitors, there are serious safety
    issues to be considered.

    --

    Jerry G.
    ======


    hi there again!

    I am repairing an old monitor (I was not able to get the serial). But
    its oldy im sure. During power on, i feel a static at the front of the
    monitor. An indication of a high voltage but after a few minutes, 4
    minutes i think, it suddenly shutdown. So I used my multimeter and
    tested the collector of HOT. I measured a voltage but when the monitor
    dies up, the voltage also disappears. I changed some bulging
    capacitors but still the problem persists.I suspect the deflection
    yoke but I have no yoke tester. I heard that running a monitor without
    deflection yoke disconnected is not good. I am a little bit lost here
    because I havent practiced it for long time now. So can anybody give
    me suggestions on how to fix this problem. I know safety precautions
    in electronics. I want friendly advise please. Thanks in advance.
     
  3. Guest

    Hi!
    Do you have a picture during this time?
    I suspect you don't. Are the CRT filaments lit?
    1. NEVER Measure the HOT collector voltage with the deflection
    working! You may, if you own a good old VOM with a 1500V (or greater)
    scale, and ONLY IN THIS SCALE!
    2. If the voltage disappears it is either a power supply problem or
    the controller is shutting down sensing some other fault. Can you turn
    the set back on with the power switch? do you need to press once or
    twice?
    I think, there is some other problem causing the micro to blank the
    video and to shutdown. Maybe vertical deflection: Turn op the SCREEN
    Control on the flyback (with the set on and the deflection running)
    and see if you get a raster or a horizontal line.
    The H-yoke is very unlikely at fault, the V-yoke is possible (in
    theory) but I've never heard of a V-yoke failure. It would suspect the
    Vertical output stages then (or a service switch)
     
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