VDU clicks/flashes to start-up in cold weather. - Hardware

This is a discussion on VDU clicks/flashes to start-up in cold weather. - Hardware ; A PC & VDU seem to have related problems: The VDU click-sounds & power-light-flashes at approx. 1 Hz before it's usable. More so in colder weather. Now [in s. hemisphere winter] it never reaches the threshold. Q - is this ...

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Thread: VDU clicks/flashes to start-up in cold weather.

  1. VDU clicks/flashes to start-up in cold weather.

    A PC & VDU seem to have related problems:

    The VDU click-sounds & power-light-flashes at approx. 1 Hz before
    it's usable. More so in colder weather. Now [in s. hemisphere winter]
    it never reaches the threshold.

    Q - is this apparent 'warm up threshold' adjustable inside the VDU ?

    I've replace the VDU - for possible later summer use;
    BUT the previously existing 'difficult to start PSU', now is a 'refusal to
    start PSU' -- also when I disconnect the replacement VDU.

    Q - what tests/measurements can I make to debug this problem ?

    == TIA


  2. Re: VDU clicks/flashes to start-up in cold weather.

    In comp.sys.ibm.pc.hardware.misc problems@gmail wrote:
    > A PC & VDU seem to have related problems:


    > The VDU click-sounds & power-light-flashes at approx. 1 Hz before
    > it's usable. More so in colder weather. Now [in s. hemisphere winter]
    > it never reaches the threshold.


    > Q - is this apparent 'warm up threshold' adjustable inside the VDU ?


    First, I am going to assume this is a CRT, not an LCD.

    This is not an intended "warm up". The clicking is typically
    relays adjusting settings to the horizontal/vertical
    frequency given in the signal from the graphics card. It
    should stabilize in less than a second. I would suspect
    electrolythe capacitors, that have aged enough to need some time
    to recover capacity (they do that to some degree when
    voltage is applied, faster so at higher temperatures because
    it is a chemical process). The way to fix this is tho find
    the proken capacitors and replace them. The poblem is identifying
    them. Without a high-quality capacitor evaluation meter that
    supports in circuit evaluation (i am nor sure these
    3even exist....) this may take forever, as you
    have to remove every electrolyte capacitor and asses it.

    > I've replace the VDU - for possible later summer use;
    > BUT the previously existing 'difficult to start PSU', now is a 'refusal to
    > start PSU' -- also when I disconnect the replacement VDU.


    I asume you mean the PSU of the VDU. This is not a start
    issue of the VDU-PSU. It is a stability problem. The other
    characteristic of aged capacitors is that the problem
    gets worse when they are not used. Don't get me wrong, they
    do degrade faster when used, but the level they perform at
    degrades to some lower point ans stabilizes there when they
    have not been used for some time.

    > Q - what tests/measurements can I make to debug this problem ?


    Classical TV repair manuals may help. Significant electronics
    experience is required. I would say this can be a >20 Hours job for
    somebody without the right experience, but with significant
    electronics knowledge. Oh, and BTW, measurements on a live CRT are
    dangerous unless you know what you are doing. There are a lot of
    desings out there that can have twice the mains voltage as DC on the
    chassis. That can be 600V. Then there is the high voltage to the CRT
    (20'000-30'000V for color) that has quite a punch behind it, since the
    CRT acts as capacitor. Not as bad as touching the wires on a medium
    voltage (typically 15'000V, but with far higher currents), power
    delivery line, but can still kill you. Definitely a ''stay away''
    zone.

    I would advise you to get a new LCD instead. If you stay at
    17" (screen space comparable to 19" CRT), you can get decent
    ones pretty cheap.

    Arno

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