[Jay Wilson]

As I recently figured out, someone made some wild adjustments to my ECP that caused me to use too much keystone. I am still using too much IMO and would like some other opinions


My screen is 52†high by 92†wide. Using the 1.5 x width, I have a 138: throw distance. A 92" 16:9 screen relates to a 69†high 4:3 screen. The difference between the 2 screens is 17, divided by 2 =8.5â€. That means I should/could be 8.5†above my 52†screen in the “normal†position. Should the projector be more or less level at this position? I am actually 6†below the top of the screen, so I should be well within specs to use no keystone…but it’s still at 6-6.5. I also have to tilt down the pj (the full 15 degrees) to get the image on the screen. I know this isn't right, but I have just now started to investigate.


So…I decided to tilt the projector up so it is level now and the bottom of the pix is in the middle of the screen. Again, I can tilt the front of the projector down, but it ends up at the full 15 degrees and I have to use the keystone. Is there something that should be checked that I'm not finding? Should I just use some mechanical "lens shimming" to get the picture where it should be? As M NEWMAN said once, at this level my pj is

dragging the ground." Any ideas?

 

[jcmccorm]

Ok Jay, I drew a "right" triangle. 34.5" on one side (center of your screen from the top edge) and 138" on the other side. The angle that your lenses need to be tilted down to hit the center of the screen is 14.5 degrees according to my calculation. So, with you PJ's lenses level with the top of your 69" screen (not 8.5" above it) you're still at 15 degrees. Sounds like you may need to go lower by 8.5".


Sound right?


Cary

 

[jcmccorm]

Oops, I just realized that 69" is your 4:3 screen. You *are* lower than the top of this! Sounds like you should be ok.


Cary

 

[jcmccorm]

Hey Jay, do you have those two metal braces that that go from the front of the PJ to the CRT top-plate on either side of the green lens?? If those are missing, you'd be way off.


Cary

 

[M NEWMAN]

That's a very good suggestion Cary. Jay, there should be either two metal panels or two wire-frame style rails that connect the CRT top bulkhead to the lower chassis that "pull" the entire bulkhead Assy forward a little. With out them, you might be getting the wrong throw. If this is confusing, pop the top covers off and shoot a picture so we can look at it to see if anything's missing.

 

[Jay Wilson]

Well, that's interesting, let me see if I follow. First, you may be on to something...those brackets are out of my pj. I removed them a year ago when I replaced the blue tube and just never put them back. BUT, If they pull the bulkhead forward, wouldn't that cause the throw to go even higher? I am imagining that the weight of the tubes/lenses pushes the bulkhead back, and causing the image to droop. Pulling it forward would lift the image. Is this what you are saying?

 

[Jay Wilson]

AND, if what I am saying is backwards, and it would lower the image, would they lower it by 26" or so?

 

[jcmccorm]

You are right Jay, the weight of the lenses (for ceiling mounted PJs) makes the bulkhead move back. So, with the brackets installed, your image would move up.


Cary

 

[Jay Wilson]

Damn...thought you guys might have fixed it.

 

[M NEWMAN]

Well, umm, actually, I think that in a ceiling mounted situation the bulkhead might in fact lean forward, instead of backwards like it does on the floor. This would give you the too high effect condition you're currently experiencing. Instead of blabbering about this endlessly, Jay just go and push/pull the CRT bulkhead using those rails to line up the holes to see if it fixes the problem. If it doesn't, and your rasters aren't shoved down against the bottom of the CRT's, then that's damn curious. I'd actually have to brainstorm a bit about what it might be, and that's really difficult when I'm drinking a beer....

 

[Jay Wilson]

Well when you're at work and not at the pj all you can do is babble endlessly. So there


I'm going to try it now...just got home and thought I'd check on any new info first. Enjoy that beer.

 

[Jay Wilson]

Well, No joy. How was that beer Mike? I reinstalled the brackets, and it didn't move the pix but about 1 " on screen. That was using the slots in the bracket...from one end to the other...1" travel on screen. So...


I took this pix, I was in process of re-dressing the wire harnesses and basically had everything apart...it looks better now...I promise. This is standing behind the pj, with the camera level to the case split. You can see

how far down the screen I am. Does this give any better clues? Other than to put everythign back together

 

[jcmccorm]

Hey Jay, you need to tilt that thing down! The center of the image on the two ECPs I've had mounted could always be sighted by following the line of the case split to the screen. Yours is aiming at the top of the screen.


Cary

 

[jcmccorm]

When you say the projector is level, do you mean that the lenses are parallel with the ceiling or the base of the PJ is parallel with the ceiling?? On mine, the base is more or less parallel with the ceiling which makes my lenses point down a bit (and aiming at the center of the screen).


Cary

 

[Jay Wilson]

I know it needs to be down a bit...I levelled the pj just so you could see easier how it sat in comparison to the screen. It does point down (whne the image is positioned) I just think it angles too much. The base of mine also sits level, but based on my screen size, how it sits, etc, etc, compared to yours, I think it it too much. In other words, your pj is a bit above your screen I think you said (or it can be according to Mikle) and mine is so low, just doesn't seem right. I guess maybe it is.

 

[Jay Wilson]

PS...Just finished vert mods...on my way to blow the....er try them out

 

[jcmccorm]

Jay, here's a couple of pics of mine. My lenses are lower than the top of the screen and my keystone is at 5.5.

http://fly.hiwaay.net/~jcmccorm/MVC-743X.JPG
http://fly.hiwaay.net/~jcmccorm/MVC-747X.JPG

 

[Jay Wilson]

thanks Cary, That's about what mine looks like when displaying. BUT, my only concern is that I should have an 8 degree angle and it's pushing the 15. My keystone is 6.5 and my pj is closer to the center than most...so...I thought maybe I was stressubg something. Maybe I should leave well enough alone Nah...that would take all the fun out of everything!

 

[M NEWMAN]

Jay,


I'm a little lost about where you're getting your angle from. Are you talking about the angle of the base as it relates to a level plane, or the CRT angle as they relate to a level plane. Its the base to level plane you should be concerned with. It sounds like you're ok to me.

 

[Jay Wilson]

I drew an imaginary triangle from the middle of the screen, through the CRTs, and then back to the top of the screen. the angle at the top of the screen is obviously 90 degrees. I then formulated that the angle of the CRT (pointing at the center of the screen) should be 8 degrees. So when I angle down the pj, the imaginary line from the top of the screen would be level...the CRTs would be angled down 8 degrees. it should actually be less than 8 degrees as I am 6" lower than the top of the screen. I am thinking to hell with it...if its close enough...I was just trying to minimize keystone, and with it at 6.5, as low as I am, just doesn't seem right.