Iiyama 21" vision master monitor crackling noise

Jan 19, 2006 6 Replies
J

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



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M

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?

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J

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

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J

sorry to disappoint, but no :-)

cheers

Jules

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J

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

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M

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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