Originally Posted by
Mossay 
Had this problem, as another guy said, the lightpath isn't completely sealed: theres actually just a piece of heat-resistant cardboard thingy sealing it off from the rest of the projector. So you used the projector for a bit, dust got collected inside, the projector was moved a bit (picked up, put down, anything), some of the dust managed to make its away over the edge of the cardboard and came to an annoying rest upon the little rectangular device that generates the image. result: dust blob!!.
If the projector is under warranty then send it back. I've had things go missing with Acer warranty returns so I bypassed them and opened up the projector and cleaned it myself. Fixed the problem temporarily but I'd be using the projector for 10+ hours a day so the problem kept recurring (I had to clean the projector 5 times including many many disassemblies). In the end I made a boo-boo which got some of the cleaning liquid caught behind the protective glass of the thing that makes the tiny image inside so the bottom right hand corner-edge is now noticeably discolored. After 40+ disassemblies the projector still functions perfectly, but I voided my warranty. All the problems I had with the H5360 from the Edid corrupting, to ports failing, to dust blobbing has put me off buying another. 3d gaming and movies were nice, but I just upgraded to the Epson8350(tw3200) for 909 ^_^ May revisit 3d at the end of next year, but for now the H5360 is relegated to my backup projector should the epson fail.
Anyways! If your out of warranty and want the benefits of my DIY repair experience (most importantly the what not to do's) Read on:
1. Taking off the case is very easy once you realise that the top of the projector (when unscrewed) slides off towards the back with some force applied. All you have to do then is look for where the front panel is slotted into the side wall and unslot by bending the plastic a bit.
2. The front panel can be a nightmare to take off sometimes, the screw-hole on the bottom side can provide some leverage by placing a screw driver a tiny bit inside it and pushing the front panel off (only the plastic at the top of the screw-hole belongs to the front panel).
3. Be very careful about the removal of the front panel because if it goes flying off all of a sudden from your attempts to remove it its likely the infra-red sensor will get its wire removed. (not the end of the world though since the top of the projector has a second sensor--where the power button is).
4. Don't be tempted to try and take out the electronic board to get easy access to the lightpath. That mo-fo just wouldn't come out for me. You MIGHT have better luck but I'll let you decide whats best.
5. Remove the grey plastic thingy for adjusting the zoom and its screwed in base.
6. Remove the lens -- 3 screws at the front, then out she comes -- will not come out if the plastic zoom thing isnt removed.
7. Get a flashlight and shine inside to the tiny panel hiding directly behind where the lens was originally placed. Find out where the tiny bit of dust is.
8. Get a can of compressed air and (with the straw attachment) gently spray from a distance of about half your index finger at where the dust is. The temptation will be to give the dust a quick powerful blast at point blank range but you could end up causing the air to condense onto the panel, which then requires you to do some extremely finicky cleaning with liquids and Q-tips.
Just send it back if its under warranty though My experience with Acer was my first H5360's hdmi port failed after 3 weeks of use. I sent it for repairs, Indian support line gave me the run around for 3 months saying it was under repair, then admitted they lost it. I got a new H5360 sent out to me which I'm pretty sure was a refurb given that how the firmware was faulty (upon resolution change the picture would only appear as one line of pixels at the bottom of the screen, had to press hide and unhide to get the picture to fix itself.. EVERY damn time. Which is why I just didn't have any desire to send the projector back to them again for repair as their support (for me) was terrble.
--Edit-- As CT-Wiebe suggested: it could just be the case that the tiny panel is fine, and theres only dust on the lens (either at the front of back of it). In that case search about for tips on cleaning lenses ^_^
If not maybe you can change your setup to non-upside down (have you tried that yet btw?) when you receive the projector back from Acer.
