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Changing LOPT in monitor...

Discussion in 'Electronic Repair' started by Mike Deblis, Apr 18, 2004.

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  1. Mike Deblis

    Mike Deblis Guest

    Hi,

    I know a bit about low voltage stuff, but I want to change the LOPT in an
    Eizo/Nanao monitor.

    I know the LOPT is faulty, as it arcs and pops when the monitor is running,
    and after much effort, I've found a spare.

    The monitor (an excellent F77) is probably not worth sending to a
    professional to replace the LOPT as the s/h value is probably only USD
    100-200...

    What do I need to know about safety in order to change the LOPT? It's
    certainly worth trying to repair as the picture quality is excellent, but
    not worth dying for !

    How do I ensure that there is no HV left in the chassis/tube before starting
    work - the monitor has not been powered up for some time (month or so) at
    the moment.

    What special tools (if any) will I need?

    I really don't like really HV stuff much (very healthy respect) and would
    appreciate the advice...

    Thanks from a slightly paranoid Mike...
     
  2. Robert Baer

    Robert Baer Guest

    Ignoring shipping charges, just to bench a monitor is $60 and
    up...rather close to the cost of a replacement.
    I have been an electronic technician for over 40 years, and never
    heard of a "LOPT".
    Housesomever, the way to render the HV on the CRT safe, is to first
    connect a wire to the chassis and/or the bare wire running around the
    outside of the tube (it is contacting the black aquadag on the outer
    surface). Make sure it cannot become disconnected.
    Then poke the other end (bare wire here) under the HV cap at the CRT
    (anode).
    Tape it down to the pix tube if you like, to ensure it will not fall
    out or be pulled out.

    Do your work.

    Remove that wire fromthe CRT anode first, and then from the
    chassis/ground wire mentioned.
     
  3. Mark (UK)

    Mark (UK) Guest

    You do monitor repairs, and have never heard of a <L>ine <O>ut<P>ut
    <T>ransformer??

    Mmmmm.
     
  4. Art

    Art Guest

    Line Out Pput (Power) Transformer ?? Another reference to the Flyback,
    Integrated High Voltage Transformer, High Voltage Transformer, Et Al Fin.
    The terminology, I believe, initially was used in Europe (British Isles ??),
    and has been used internationally for quite a period of time.
    I've been involved in Consumer Electronic Device Repairs since the early
    60's and ran into this nomenclature in the late 70's while reading some
    technical reference manuals from Phillips Corporation. The term has become
    interchangeable in the service world because many of us "TV Techs" have
    migrated to servicing many other devices, inclusive of computer power
    supplies, monitors, video control and switching devices, etc.
    It is mandated that the Professionals in these service positions keep
    abreast of the changes in technology, inclusive of the terms and references
    currently in use. Also the changes in electronic schematic drawings and
    diagrams that use visual indications and pictorials not base specifically on
    the "Old US Standards". Ok Enuf!! Thanks & Cheers Gov
     
  5. Jerry G.

    Jerry G. Guest

    For your safety, send the monitor out for service, to do any work in it.
    After changing the flyback, there are a number of safety and operation tests
    to do. You will not have access to the necessary equipment at home for this.
    It takes more than a simple DVM to work on these.

    There are issues for testing and adjusting the HV at the anode, testing the
    hold down current and HV safety cut-off, testing the performance of the main
    power supply, and etc. There is then the set-up of the CRT screen voltage,
    and the beam focus set-up.

    If the HV is too high, there is risk of X-Ray radiation exposure. Some
    people tend to smirk at this one, but if you venture in to the safety issues
    concerning CRT monitors, this is a very serious thing.

    --

    Greetings,

    Jerry Greenberg GLG Technologies GLG
    =========================================
    WebPage http://www.zoom-one.com
    Electronics http://www.zoom-one.com/electron.htm
    =========================================


    Hi,

    I know a bit about low voltage stuff, but I want to change the LOPT in an
    Eizo/Nanao monitor.

    I know the LOPT is faulty, as it arcs and pops when the monitor is running,
    and after much effort, I've found a spare.

    The monitor (an excellent F77) is probably not worth sending to a
    professional to replace the LOPT as the s/h value is probably only USD
    100-200...

    What do I need to know about safety in order to change the LOPT? It's
    certainly worth trying to repair as the picture quality is excellent, but
    not worth dying for !

    How do I ensure that there is no HV left in the chassis/tube before starting
    work - the monitor has not been powered up for some time (month or so) at
    the moment.

    What special tools (if any) will I need?

    I really don't like really HV stuff much (very healthy respect) and would
    appreciate the advice...

    Thanks from a slightly paranoid Mike...
     
  6. I had never heard it called that, either. I still don't know what it means.
    Do you mean what we call "power transformer" (which takes the incoming AC
    from the line)?
     
  7. Mike Deblis

    Mike Deblis Guest

    Alright already! Over here, a LOPT = Line Output Transformer = Flyback
    Transformer = FBT

    Paranoid Mike
     
  8. No.
    The 'line output transformer', operates from the horizontal deflection
    'line' drive, in flyback mode, with a voltage multiplier, to generate the
    main HT voltage for the tube (hence 'line', and 'output'). As has been said,
    changing this, involves resetting most of the high voltage adjustments
    around the tube, and implies having th correct manual with the
    voltages/tests required, and a suitable high voltage probe for the
    testmeter/scope.

    Best Wishes
     
  9. And you actually believe that all professional servicers or even most do
    these tests? Geez!
    I do agree that in this case where arcing was the original symptom,
    at least a test of the HV after repair should be made to assure that it
    isn't excessive.

    --- sam | Sci.Electronics.Repair FAQ Home Page: http://www.repairfaq.org/
    Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
    +Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
    | Mirror Site Info: http://www.repairfaq.org/REPAIR/F_mirror.html

    Important: The email address in this message header may no longer work. To
    contact me, please use the feedback form on the S.E.R FAQ Web sites.
     
  10. Robert Baer

    Robert Baer Guest

    I do know what a line output transformer is, and most places *and
    functions ) where they may be used: 1) audio work - mostly Public
    Address (PA) systems; 2) the term sometimes is loosely used in RF power
    and/or distribution amplifiers; 3) again more loosely used for
    transformers in Ethernet and similar communications work.
    However, of the many hundreds of computer monitors i have seen, *NOT
    ONE* had any such thing and none of them could possibly use such a
    thing.
    Perhaps you are referring to either (1) the power transformer (from
    the incoming power line) - if it had one of them at all; OR (2) the
    *flyback* transformer.
     
  11. Robert Baer

    Robert Baer Guest

    And, like i said, it costs $60 or more, just to "bench" them; and a
    replacement would not cost a lot more...
     
  12. Line Output Transformer, pronounced "loptie".

    It's what monitor techies in the UK call a flyback transformer.
    Strictly speaking, I think the word 'flyback' is more correct, since
    these transformers operate on the flyback principle.

    The term 'Line output' comes from the earlier days of TV sets, when a
    conventional transformer was used to boost the horiz pulse to about 9kV,
    which was then amplified by a tripler module to produce the final anode
    voltage.
     
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