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Iiyama 21" vision master monitor crackling noise

Discussion in 'Electronic Repair' started by Jules, Jan 19, 2006.

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  1. Jules

    Jules Guest

    Over the last couple of weeks my Iiyama 21" Vision Master (MT-9021)
    monitor's started making a series of sharp crackles when being turned
    on or off, and occasionally it's completely lost picture for a fraction of
    a second (also accompanied by a loud crack).

    Certainly sounds like something's arcing where it shouldn't be - I'm
    pretty sure the noise isn't coming from any of the relays. There's no
    visible arc though in a dark room with the case off when the screen's
    turned on or off.

    Internal short in the flyback? Any common failure points in these
    particular displays related to these sorts of symptoms?

    The display seems to be having voltage regulation trouble too - there
    seems to be quite a bit of 'bounce' when changing from a dark to light
    screen. Unfortunately I can't be certain that it wasn't there before these
    HV troubles started.

    No sign of bulging / leaking caps, but I haven't got to the point of doing
    any real tests yet - thought I'd ask group wisdom first!

    cheers

    Jules
     
  2. Mr. Land

    Mr. Land Guest

    You've watched the chassis with the cover off in a darkened room and
    can't see any arcing? How about the board plugging into the tube? G2
    arcing perhaps?
     
  3. Jules

    Jules Guest

    Nope. There are a few occasional mild-looking arcs from the yoke clamp
    screw - apparently to the yoke body itself - when the monitor's turned
    off. I'm not sure what to make of those - they're not in sync with any of
    the louder cracking noises (and don't happen nearly as often) so are
    presumably either a secondary effect of whatever the main fault is or just
    natural discharging from shutting off (may always have been there for all
    I know)

    The monitor's a bit dusty inside, although I've seen far worse - I'll give
    it a good blast with an air compressor later I think and blow the dirt out
    just in case that is the problem (plus also check any grounding points etc.)

    I can pick up a spare 19" screen tomorrow which at least means I can take
    my time diagnosing the problem with this display :)

    cheers

    Jules
     
  4. John K

    John K Guest

    Jules? From a dot f?
     
  5. Jules

    Jules Guest

    sorry to disappoint, but no :)

    cheers

    Jules
     
  6. Jules

    Jules Guest

    Hmm, well no luck - same problem.

    I'm tempted to remove the flyback and check for signs of arcing
    underneath (in which case a repair that'll hold *might* be possible), but
    it's looking like I need a new flyback...

    Without the service manual, the only labelled test point is 130V just
    downstream of the PSU - that's sitting at 128V on my display, which is
    *probably* within tolerance (there is a pot to adjust it, so I'll try
    tweaking it slightly just in case)

    cheers

    Jules
     
  7. Mr. Land

    Mr. Land Guest

    Pardon if this is a stupid question but did you try any Internet-wide
    searches using the monitor model number?

    I did this just for fun with a recent monitor I had that went dead, and
    was shocked to find a site that had the full schematic for download for
    free.

    Using that I was able to locate a burned-out $3 SCR and the monitor's
    back in service.

    Hope you have equal luck...
     
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