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-   -   Old LCD Projector and the Diagonally Uneven Focus (Among other woes...) (http://www.avsforum.com/forum/68-digital-projectors-under-3-000-usd-msrp/1524285-old-lcd-projector-diagonally-uneven-focus-among-other-woes.html)

aquariumguy 03-25-2014 02:35 PM

 

 

I'm poor so I bought an old NEC LT380 1024x768 LCD projector off Craigslist for cheap until I can get a modern 1080p projector. Being a novice, I didn't notice some things while speedily checking the thing out.

 

1) If I focus towards the top, the bottom becomes unfocused. Eventually I realized the top-left seemed to oppose the bottom-right corner. If I focus toward the center, the picture blurs outward and moreso towards those directions than the other corners. It has me imagining something angled diagonally so that one corner is further while the other is nearer.

 

2) Slight yellow tint. Came here and learned about LCD projectors and the faster degradation of blue polarizers that seem to typically become noticeable after about 5000 hours of usage (which mine happens to be at).

 

3) Slight red-ish edge on picture appeared first at the top, then moved to the right side of the picture. EDIT: I did my homework there, too, and learned this is very likely dust on the polarizers or lcd panels and has been remedied by many with a compressed air cleaning.

 

So, I decided to open up the projector and clean everything. I'm unwilling to invest more money into an outdated projector not even ideal for movies, and buying one for parts seems pointless as it would likely be just as used up. Whatever is the picture I can get with a cleaning is what will do until the day I can get a new one.

 

Unfortunately, as seasoned people may see, I messed with the LCD panels on the optical block. So, after doing some video watching and forum reading, I have determined I'll employ forceps to tediously rectify my error and get the red, green, and blue back in place since unfortunately, the LT380 does not let me have easy access to the panels while it's out. I haven't gotten to test it out as its colors are all zonked out, but I think I haven't noticed a red-ish edge...

 

Now, since I have it open, the last thing I can't figure out, is what the hell could be causing the uneven focus, and if there is any way for me to fix that. I found a couple threads here on the issue. First order of advice is to make sure the projector is completely perpendicular and centered and all that to your surface. I have tried tilting and angling every which way and I see no change in the uneven focus. I followed the next advice and held up a paper and brought it closer to see if there was actually an uneven focal point. Unfortunately, it seems so (see pics). I recall someone saying that it could be something situated incorrectly with the optical block. In my pics, the picture is focused to the bottom-right corner while the paper is a few feet closer, - about 75cm/29.5in from the projector.

 

Can someone offer any ideas of what would cause this and how to fix it? So far, I've been unable to spot anything on my own. It's really the last blemish to this purchase and of course it would be nice to get to watch a sharp picture and not a hazy one. I don't even mind the possible slight yellow tint as it seems like I could correct that with the video card settings on my computer.

 

In my cleaning, I opened up the compartment with all the mirrors and color filters, wiped all of that, blew compressed air at all of it, cleaned every lens, filter, or similar type thing. I separated the optical block from the lens and was only able to open one layer of the projector lens and cleaned it but couldn't figure out how to go further (and was wary to).

 

Help a ripped-off poor guy out. Please!


Bohanna 03-25-2014 05:06 PM

Sorry dude but messing with the Panels was the wrong thing to do. Looks like your convergence is off big time. The reason for the uneven focus could be the front lens was bashed and it won't track evenly. it could be a matter of pulling it into place. Try moving the lens in and out and see if it moves freely. My guess is the Blue screen is an issue since you mentioned it already This presents itself as a yellow ting to a yellow spot so you are already fighting a loosing battle. As far as the convergence goes,, if there is one panel that you haven't moved or touched yet try working off that one and align the panels one at a time while blocking the panel you are not working on or you will go crazy trying to make all three converge at the same time. For example. work off the rear center to the panel on the right and put up a grid align the right panel and block it off with a cut up match book or Business card then work on the left panel. Once it lines up with the rear panel remove the light block and see how the overall convergence is. BTW Do this from a distance of five or six feet or project a 40 to 50 inch image Don't use a huge screen it will only confuse you.

Bohanna

aquariumguy 03-27-2014 10:55 PM

Thanks for the response Bohanna.

 

I'm not too worried about the convergence issue. I got some forceps in to help me re-align everything. It'll be a pain, but I'm okay fidgeting with it until I get it right.

 

I couldn't spot anything wrong with the lens so I removed the optical block to look at it and I think I found the culprit (thankfully)! Take a look:

 

 

It looks like the right side is raised above that black ridge, with the bottom-right sticking up furthest. That seems to match up with the projected images manner of uneveness. The problem is, I can't figure out how to push it down. I tried just shoving it down hoping it was something merely hanging out of whack, but it's firmly sprung up like this. I can't figure out how to remove it from the black frame to re-situate it.

 

Ideas?

 

UPDATE:

 

Okay, so I soon after learned what I was looking at was the prism that is unevenly set. After a while, I finally found that when I turned the prism portion in a certain direction, it was creaking, so I went for it and voila - it came off the frame. I don't know how these are assembled, but I'm guessing this is more like a lazy fixing attempt by someone in the past (I can see a sticker on the bottom of the projector from some repair shop in PA):

 

 

Looks like it was glued. I chipped off some and I have some 5 min. epoxy I'm guessing I could use to glue it back properly. You can see on the bottom that would face toward the lens that there is some sort of blemish on the edge. That's the edge toward the glued top. I'd seen it before when I was cleaning, and now I know what made it... Surprisingly, I don't have any defect in the picture from that as far as I have noticed so far.

 

I'll update this later, I guess. Not sure I want to glue the thing back together but I guess that's really the only solid way.


aquariumguy 03-28-2014 03:12 AM

Gluing the prism so that both sides touch the black frame does fix the uneven focus! Hooray - but, that red right edge of the screen (see first post pics of the grid) is still there and I can't figure out what's causing it. I guess it's the red right edge I saw when I first got the projector, but after cleaning it, it's now a big bar. Before, it was just a slight glow/line of the edge itself. I was messing with the convergence earlier and moving any of the red, green, or blue panels doesn't affect that red right edge...

 

I got all the panels lined up pretty quick but then I guess the glue is still susceptible to the high heat and the whole optical block started moving as I pushed around the panels, so I will come back to it later once I've let it cure.

 

UPDATE: Have found this: http://www.avsforum.com/t/1458911/epson-8100-replaced-bulb-and-now-pink-blue-bands#post_22982807

 

Will investigate further.


Ftoast 03-28-2014 05:54 AM

It looks like that right side's green panel is dim, but still present. Is that side of the green being bounced off of something that's only partially reflective or is it possible there's something partially blocking or fogging just that green right side? I hope it isn't the green's LCD itself that has a partial block.

Hey, you now have a carefully hand-aligned PJ..that's something people pay good money for. biggrin.gif

aquariumguy 03-28-2014 01:40 PM

Ftoast,

 

That's what I thought about it being the green panel, but when I move it around, the green grid pattern moves, but the shadow stays in place on the ride side. I'm guessing it's something else, somewhere else.

 

Tinman's post I linked to in my last post seemed promising, but now I've opened up that area and can't see anything out of place. Everything seems snugly in place with no way to move it... But there must be something outside of the LCD panels that are off-center...

 

Here's what I'm seeing:

 

 

The only thing I haven't touched is the little screens (don't know what they are - other polarizers?) between the LCD panels and the prism, but they look alright.


Bohanna 03-29-2014 04:29 PM

Like I said earlier the Main lens must have been pushed into the optical block. I have seen this type of damage several times when the person carrying it like a suitcase walks into a door or a wall and it gets smushed in . I think this is one of the reasons they try to recess the lens into the case so if it hits something the case will take the impact. Now that you have this solved. I would work on the LCD panels and stay away from the optical path. The colored glass is polarised and fits facing a certain direction. If you get it wrong your even more screwed!!- Bohanna

BTW the three little colored screens that are in front of the LCD panels are the Polarisers.


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