Tip & How-To about LG RD-JT91 Multimedia Projector

Mirror or light tunnel collapsing

A weakness that you might experience with your projector is the collapsing of the light or mirror tunnel. Not sure if this is common to DLP projectors only. The symptom is that you see grey bands or shadows on the edge of the TV image - this is caused by a mirror getting in the way of the bulb light. The glue holding the mirrors together seems to weaken over time (3000 lamp hours in my case) and causes one or more of the mirrors to loose its position. For solution, search for "mirror tunnel" or "light tunnel" under all projectors. The problem seems to be quite widespread. I managed to fix my LG's.

I wonder why the manufacturers don't use a rectangular glass tube that is mirror plated on the long sides ?!?! Suppose they want to sell new projectors after lamp or mirror tunnel expiry!

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I have a white line that appears, varies in width, and will sometimes disappear.

if the line has a hazy edge, it may be that the light tunnel is collapsing or the dlp wheel needs to be replaced. if it is hard edged, it may be the dlp chip is bad.

May 10, 2012 | Sharp XR-1S Notevision DLP Projector, 800...

1 Answer

The right vertical side of the projected picture seems to be slightly shadowed. Is this the lens or for some strange reason is the bulb going out? It only has about 200-300 hours of use on it

if you have the dp6150 (lcd projector), you have a lens or mirror out of alignment, or something obstructing the light from the inside. if you have a dlp projector (not the dp6150), the light tunnel has collapsed and needs to be replaced. you can get the part from an infocus service center (like av solutions in ny), or send it to them for repair. they're really good. www.avsolutionsny.com

Jan 12, 2010 | InFocus Proxima DP6150 Multimedia...

2 Answers

Tranlucent dark spot on Optoma image. Looks like something is on the lens.Off center--top to bottom. Cleaned lens, blew out case, changed bulb, still with dark spot.

is it an optoma or an infocus? if it is the infocus, it needs to be replaced. however, to replace it, you need to remove the entire optical engine. now off of that, remove the clorwheel and clip, the main board, and the tunnel (on this model it is called an integrator rod) assembly. to get that out, remove the 3 tap screws and the large screw. once you can slide it out, remove the foil from the front, slide out the inside tunnel assembly, remove the clip, then the tunnel. because the clip is an exact fit, you cannot have anything on the tunnel that increases the size. reverse the instructions to reassemble (but you will need to replace the foil with a new one). warning: you now need to realign the tunnel using 2 of the tap screws. if you have not done this before, it is very difficult and dangerous, as you need to have the projector powered on and the screws are way inside next to the power supply. there is a risk of electrocution and damage to the projector. best bet- send it in to an authorized infocus service center for repair. try av solutions in ny. they're really good. www.avsolutionsny.com

Nov 15, 2009 | InFocus LP70+ Multimedia Projector

6 Answers

infocus x3 video problem

Sounds like it could be the mirror tunnel. There is a very small mirror tunnel behind the color wheel (looks like a long prism) that can often fail as it is very fragile. This tunnel concentrates and channels the light to the DLP chip and if it collapses it can cause the very issue you describe.

Feb 18, 2008 | InFocus X1 Multimedia Projector

2 Answers

glass prism


Thanks for contacting us regarding your product questions or concerns. It appears you are wanting to know how to reach the glass prism from your 4805?

My initial question would be, why are you looking to access the glass prism in your 4805? This is a very dilicate process internally of your projector which helps it opperate. Are you trying to self-repair your projector?

Let me know. I'll be waiting for your reply.

Dec 28, 2007 | InFocus ScreenPlay 4805 Multimedia...

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