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Someone please solve LCD PJ dust blob problem

417 Views 11 Replies 7 Participants Last post by  DanHouck
Two weeks with my VT 540 and a green blob appears in the right upper corner. I have reviewed all past posts; vacuuming and compressed air have been mentioned as possible solutions but still no definitive answers. So my specific questions:

1) Are these the only two options? If so, which one is better?

2) Has anyone actually been successful in removing these green dots?

3) Whichever option you suggest, please also explain "how" to do the procedure? (which panels to open to gain access? etc.)

Greatly appreciate responses. I am sure this will help several members "de-blob" their headaches.

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Well you have the options of...

Vacuuming from the outside through the vents or

Blowing compressed air in through the vents..

Both Non destructive and warrantee proof or..

Opening the PJ up and blowing compressed air inside which I think voids warrantees..

I have opened mine up many times and it needs another now / soon...

Some things to mention.. The first time I did this I used compressed air from a camera shop and had a nightmare when it squirted out a load of liquid propellant (they have a tendency to do this) all over the DMD resulting in smears !! I had to really strip it down then to clean the DMD with isopropyl alcohol... Since then I have discovered a really neat little kit sold for cleaning out dust in keyboards and PC components.. It comes with a little 'trigger' gun and uses those compressed gas 'bullets' like old soda stream machines used (remember them http://www.avsforum.com/ubb/smile.gif )... This is a far far better solution all together...

I will dig the kit out and see if it has company name / url on package as it really is a perfect PJ cleaning tool !!


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HTPC without using windows... GUI Front Ends for Home Theater
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Thanks much http://www.avsforum.com/ubb/smile.gif . I will try vacuuming first and report if it worked.


Originally posted by Phat Phreddy:
<snip>The first time I did this I used compressed air from a camera shop and had a nightmare when it squirted out a load of liquid propellant (they have a tendency to do this) all over the DMD resulting in smears !! </snip>
To help avoid the propellant issue, release about 1/3 of the propellant from the can* (you will be able to feel the colder liquid inside to guage what 1/3 is) before getting it anywhere near your projector. Then, while spraying make absolutey sure that the can remains upright and you should have no problems.

*note - you should let the can sit a wihle after releasing a bunch of propellant, so the can / nozzle are closer to room temperature, this will hep ensure complete vaporization of the liquid in the can as it is expelled.



Darren Rogers
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I have the same issue with my new Sanyo XP21 (green blob showed up on day 2). I have assumed that the LCD chips are in some way sealed: Is this NOT the case? Would the approach that Phat Phreddy describes (simply blowing in air) have any effect with my Sanyo? If so, are there any directions or schematics out there that could improve my chances of success?

Glad to report the big blob is gone after vacuuming; sadly a much smaller blob has appeared elsewhere. I guess the vacuum wasn't able to suck out the dust particles completely. I will give it another try with the vacuum before following Darren's directions on using compressed air.


My take on this blob/dot problem (after going through the various posts) is that green blobs not matching the pixel boundary are dust particles that can be removed using one of the methods mentioned above. On the other hand a blue dot (some have mentioned red) confined exactly within a pixel is a dead pixel. Although no one has yet mentioned a procedure to resuscitate a dead pixel in this forum, I have heard elsewhere that leaving the projector on overnight can "awaken" the non-responding pixel.

Your problem seems to be of dust on the LCD panel. You can probably remove the dust following the above procedures.

Hope this helps.

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When my VT540 developed a dust blob I tried vacuuming through both filters to no avail. I then took out the filters, and vacuumed, also to no avail. I then tried to dissassemble the projector, and couldn't really get it apart to see the LCD panels, even though I took out every screw I could find as well as the bulb(anyone know how? would be much appreciated).

I called NEC, got a repair authorization ($100 for cleaning), and was about to ship it out, when I gave it one last try by vacuuming through the filters again, as the manual reccommends. Lo and behold, my blob went away, but now I had a new (smaller) one. In a fit of frustration, I tried one more time. Eureka! Everything is now clean, no blobs (for the moment). The moral of the story appears to be if at first you don't succeed...

There must be a way to open this thing up, however.
Sorry to bump this thread, but I have a different problem now. There is a 2.5" diameter greenish blotch, very dim, well demarcated, a foot each from the top and the right side. Only visible on blue screen. I have tried vacuuming again - doesn't work. Looking through the lens (at an angle) I can make out a dark spot on the back side of the lens. nay suggestions?? Will compressed air take care of the problem or will I have to send it to NEC for service?

drmyeyes, I gather NEC charges $100 for cleaning. Is this true or is your warranty over.

Appreciate some advice here.

Along the lines of some of the above discussions, is there a projector "manual" out there that describes procedures for opening and cleaning, etc? Sounds like a good idea for an FAQ??? I'd sure like something specific for my XP21 but would be happy with some general instructions!

Cleaning is not a warranty covered service. I don't think this is really unreasonable (not sure about $100, though), but it should be easier to do-it-yourself.

If anyone figures out how, please post.

1. Get a can of compressed air and blow it down 1/3rd first.

2. Remove filter from projector, clean thoroughly and use a crack tool with a vacuum cleaner to thoroughly clean the area under the filter.

3. Take top off of projector and gently turn it on it's side on a clean, flat surface. You'll easily see the DMD assembly, consisting of 3 panels at right angles to each other, and the back of the output lens. Putting the projector on its side makes it easy to hold the can of compressed air level. It also helps the dust to blow out and away from the projector.

4. Clean the inside of the cover with the vacuum using the soft brush tool.

5. HOLDING THE CAN LEVEL AND NOT MOVING IT AROUND RAPIDLY OR JERKING IT blow all in and around the indside of the projector, doing the DMDs and rear of the lens assembly LAST.

6. Put the projector upright and carefully reinstall the cover.

7. Hereafter, vacuum the underside of your projector about once per week, using the vaccum to "back suck" the filter. I don't remove the filter as it might dislodge dust.

This operation will take no more than 15 minutes. I've done it twice to my Sanyo XP21N in a year.

email me at [email protected] if you have any questions.

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