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I have to heat up my CRT??

Discussion in 'Electronic Repair' started by Rachel85, Nov 21, 2007.

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  1. Rachel85

    Rachel85 Guest

    Hi,
    I was wondering if anyone could shed some light my problem.

    When my monitor was working correctly, I would plug in the monitor on,
    the green power light would come on for a second, then it would turn
    amber (power down, I believe).

    Now when I plug the monitor on the power light simply flashes and
    there is clicking noise, I have to repeatedly turn the monitor on and
    off at the plug switch to get it to eventually come on properly. I
    noticed this was worse in cold weather or in the morning when it was
    cold.

    I tried an experiment, I placed a fan heater a couple of feet away
    from the monitor and switched it on for 15 minutes then turned the
    monitor on, It came on as normal. I've tried this a few times now,
    even in the morning and it comes on as normal. So when I warm my
    monitor up in this way it starts as normal.

    I was wondering if anyone had any ideas what the problem might be.

    thanks,
    Rachel


    17" Relisys CRT
     
  2. Ron(UK)

    Ron(UK) Guest

    It`s most likely a failed capacitor in the power supply. Unless you are
    confident with working on high voltage circuits, you need to take it to
    an engineer.



    Ron(UK)
     
  3. Arfa Daily

    Arfa Daily Guest

    Agreed all points

    Arfa
     
  4. I would add solder connections to the list of suspects.

    Mark Z.
     
  5. Art

    Art Guest

    As posted, it could and very well may be defective electrolytic capacitors
    within the power supplies and or any where else within the item, inclusive
    of the deflection and regulation circuits. Proper use of an ESR Meter for
    diagnosticts is mandated. Also, as posted, if you are not sure of how to
    disassemble and actually attempt repairs, the rest is left up to the
    professionals. Cheers!
     
  6. ciscodsl

    ciscodsl Guest

    Evaluate your options carefully. Professional repair costs have to be
    weighed against replacement costs. These days there are many many used
    CRTs available for very low cost or even free. This is in part due to
    the availability of LCD type computer monitors.

    ciscodsl
     
  7. Rachel85

    Rachel85 Guest

    Thanks for all the replies, they have been very helpful,

    thanks,
    Rachel :)
     
  8. mc

    mc Guest

    It is common for loose connections (especially bad solder joints) to be
    affected by thermal expansion and contraction.
     
  9. mc

    mc Guest

    I tried an experiment, I placed a fan heater a couple of feet away
    What's the connection between capacitor performance and temperature?
     
  10. Arfa Daily

    Arfa Daily Guest

    When electrolytics are dying through high ESR, as they often do when they
    approach the end of their service life - see the interesting discussions on
    this in thread "Which DVD player is more reliable" further down the list,
    started on 18th Nov by Bob Hoffman - they tend to be much worse when cold
    than when warm. Once you have got the cap up at enough of a temperature to
    get it back in spec enough for the power supply to start up, it becomes
    self-sustaining through self heating of the cap from the high frequency
    current that they tend to pass in SMPS applications, and also from radiated
    heat from nearby hot-running components. All is then well until next time
    it's left to get cold. It's the reason why so many customers bring stuff in
    for repair with the story that it was working fine until they went away on
    holiday, and shut everything down, and then the DVD / VCR / sat box /
    computer (sub your own equipment item) didn't ever work again when they put
    the power back on.

    Arfa
     
  11. James Sweet

    James Sweet Guest


    And if you keep using it like that, further damage will eventually occur.
     
  12. James Sweet

    James Sweet Guest

    While I haven't looked into the actual chemistry, ESR drops as temperature
    rises, so bad electrolytics usually are a lot worse when cold.
     
  13. James Sweet

    James Sweet Guest

    I repaired a 17" CRT the other night, but really it was only because I can.
    Nanao Flexscan F550i, had no green. Found several leaking electrolytic
    capacitors on the input board with a corroded mess around them and a shorted
    diode in the green video amp. Good mental exercise if nothing else, the
    monitor looks better than it has in years.
     
  14. JANA

    JANA Guest

    Some component(s) in the power supply, most likely some capacitors, have
    become thermo sensitive. Take the monitor to a service centre for them to
    locate the defective part(s) and replace them.

    I don't suggest for you to try to service this yourself. It takes service
    experience, and there are serious safety issues involved.

    --

    JANA
    _____


    Hi,
    I was wondering if anyone could shed some light my problem.

    When my monitor was working correctly, I would plug in the monitor on,
    the green power light would come on for a second, then it would turn
    amber (power down, I believe).

    Now when I plug the monitor on the power light simply flashes and
    there is clicking noise, I have to repeatedly turn the monitor on and
    off at the plug switch to get it to eventually come on properly. I
    noticed this was worse in cold weather or in the morning when it was
    cold.

    I tried an experiment, I placed a fan heater a couple of feet away
    from the monitor and switched it on for 15 minutes then turned the
    monitor on, It came on as normal. I've tried this a few times now,
    even in the morning and it comes on as normal. So when I warm my
    monitor up in this way it starts as normal.

    I was wondering if anyone had any ideas what the problem might be.

    thanks,
    Rachel


    17" Relisys CRT
     
  15. mc

    mc Guest

    Yes. If you're lucky, you'll find a technician who has seen this problem
    before and knows exactly which part is the failure-prone one in your piece
    of equipment.
     
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