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

This is a discussion on Re: VDU clicks/flashes to start-up in cold weather. - Hardware ; 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] > ...

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

  1. 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 ?


    Arno Wagner wrote:
    > First, I am going to assume this is a CRT, not an LCD.
    >

    Yes.

    > 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.


    OK, on a good VDU I notice the power/screen-save mode
    time-out & re-activate toggles this. So I could just hack the
    VDU's circuit to have it permanently 'on'.

    > 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 assess it.
    >

    Perhaps a visual will reveal the bad elco.
    Or just replace some/all.

    > > 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.


    No it's the PC PSU.

    > 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 and stabilizes there when they
    > have not been used for some time.
    >

    When after running constantly for months, it's difficult to restart
    after it's been off for a day; and starting is erratic you first suspect
    temperature or a possible mains fluctuation. Ie. some parameter
    which can vary over 24 hours. But I guess it's another dud elco.
    I'd much prefer to bypass the troublesome feedback loops and
    just have a direct mains switch, like in the old days.

    > > 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.
    >

    Yes, I don't probe near ETH.

    > 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.


    Thanks. Remember that inet is global; so I might be writing for
    some remote island, which has a different price structure to the
    US. That's why the US got it's arse kicked in Iraqu: because they
    simplictically believed that all conditions are like their's.


    == crg.


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

    problems@gmail wrote:

    > In comp.sys.ibm.pc.hardware.misc problems@gmail wrote:


    > Arno Wagner wrote:
    >> First, I am going to assume this is a CRT, not an LCD.
    >>

    > Yes.
    >

    .....
    > OK, on a good VDU I notice the power/screen-save mode
    > time-out & re-activate toggles this. So I could just hack the
    > VDU's circuit to have it permanently 'on'.
    >

    Beware. The relay is triggered by some safety circuit as well. It turns off
    the HV part of the CRT (and the heaters).

    >> 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

    .....
    Maybe, could as well be your CRT is clogged with dustbunnies and
    half-shortcircueted.

    > Perhaps a visual will reveal the bad elco.
    > Or just replace some/all.
    >

    These are special elkos, you won't find them in the next hardware store.
    But doing a visual inspection of the CRT innards - after having mains
    unplugged overnight, and with a good vacuum cleaner prepared - can
    sometimes work wonders.

    .......
    >
    >> I asume you mean the PSU of the VDU.

    >
    > No it's the PC PSU.
    >

    Well, the first troubles were the CRT PSU - now it is coincidence time ...

    ......
    > When after running constantly for months, it's difficult to restart
    > after it's been off for a day; and starting is erratic you first suspect
    > temperature or a possible mains fluctuation. Ie. some parameter
    > which can vary over 24 hours. But I guess it's another dud elco.
    > I'd much prefer to bypass the troublesome feedback loops and
    > just have a direct mains switch, like in the old days.
    >

    Open the case, reseat your connectors.
    Could your mains voltage, by any chance, be somehow out of limits (maybe too
    low)?
    Standard PC psus are cheap, you may even borrow one for testing. Not onle
    the PSU may fail, there are converters on the mainboard/near the CPU as
    well.
    Even some other part (typically) drawing (too) much (startup) current, like
    graphics adapter, the harddrive(s) or tv cards, can cause such failures
    with a weak or slowly dying powersupply.
    If you can remove such a device temporarily for debugging, try that.

    --
    vista policy violation: Microsoft optical mouse found penguin patterns
    on mousepad. Partition scan in progress to remove offending
    incompatible products. Reactivate MS software.
    Linux 2.6.24. [LinuxCounter#295241,ICQ#4918962]

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

    In comp.sys.ibm.pc.hardware.misc problems@gmail wrote:
    > 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 ?


    > Arno Wagner wrote:
    >> First, I am going to assume this is a CRT, not an LCD.
    >>

    > Yes.


    >> 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.


    > OK, on a good VDU I notice the power/screen-save mode
    > time-out & re-activate toggles this. So I could just hack the
    > VDU's circuit to have it permanently 'on'.


    That could work, if there there is no frequency
    adjustment involved, or you fix it to the right setting
    there as well.

    >> 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 assess it.
    >>

    > Perhaps a visual will reveal the bad elco.


    Unlikely, unless this is a late instance of the "capacitor
    plague" (http://en.wikipedia.org/wiki/Capacitor_plague).

    > Or just replace some/all.


    That is something that can work.

    >> > 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.


    > No it's the PC PSU.


    So your PC PSU has an issue as well?



    >> 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 and stabilizes there when they
    >> have not been used for some time.
    >>

    > When after running constantly for months, it's difficult to restart
    > after it's been off for a day;


    As expected. If the capacitor is really bad, it can drop down to
    minimal performance within hours.

    > and starting is erratic you first suspect
    > temperature or a possible mains fluctuation. Ie. some parameter
    > which can vary over 24 hours. But I guess it's another dud elco.
    > I'd much prefer to bypass the troublesome feedback loops and
    > just have a direct mains switch, like in the old days.


    Direct switches have advantages. I like them too.

    >> > 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.
    >>

    > Yes, I don't probe near ETH.


    >> 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.


    > Thanks. Remember that inet is global; so I might be writing for
    > some remote island, which has a different price structure to the
    > US. That's why the US got it's arse kicked in Iraqu: because they
    > simplictically believed that all conditions are like their's.


    I know. I am posting from Europe. Actually conditions here are far,
    dar better than in the US, and we tend to thing of the US as
    a bizzare mixture of 1st and 3rd world.

    If you got this computer used, then you should try to get a different
    display used as well. I don't think trying to repair it is worthwhile,
    as basically all electrolyte capacitors will have degraded and even if
    you fix the right one, the thing may break down pretty fast again. Also,
    without decent soldering and measurement tools (more expensive than a
    cheap LCD anywhere in the world) such a repair attempt would be hell.

    Arno


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