| Duo |
I'm wondering, would it be very hard to use the projector out of a rear projection tv on a front projection screen of a relatively larger size and still achieve decent convergence and focus?
I'm seriously contemplating using mine for this since the screen on my tv has a terrible blemish in the bottom left hand corner of the plastic.
I figure a white screen would have a much better contrast and gain than the tranmissive plastic lense anyway.
Any comment on this?
I'm probably going to try it anyway.:devilr: |
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| ancorp |
Actually the contrast will probably be worse on a white screen, especially with lights on. Also Ive seen RPTV screens with gains up to 7.5! A standard white screen is 1.0, 1.3-1.6 if its a decent one.
Also you will have to flip the image sideways somehow, either by removing a mirror and rotating the proejctor, or adding another mirror, or flipping the yoke wires on each tube.
I think it would focus and converge just fine on a larger screen.
Just take off the projection screen, and try to focus it at like 100 inches on your wall.
I want to see the results! |
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| Duo |
yeah, I'll definitely have to try that one out for sure.
It is certainly easy to remove the complete projector and run it out of the cabinet. Obviously for service reasons. (I have repaired this set twice before when it belonged to its original owner.
I'm familiar with the 50 convergence adjustments and that so that's not a problem. I think I'll have to re-angle the tubes in the chassis, since they're really going to have to widen up for the longer distance.
As far as reversing yoke wires, that's not difficult, however, it is dangerous. I've done it before, but then, I know how to do it safely... (I know the uppers don't like talk of that on diyaudio and I can respect that so I'll leave it alone.)
But come to think of it, if the projector is out of the box, without the original mirror, I think it's be the right way around anyway.
I recall that during a test out of the cabinet, the text projected on the cieling was in the right orientation to be read forward. |
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| ancorp |
Nice. Yes, the tube have to be widened up.
Hey you wouldnt happen to have any spare optic parts around would you? (im looking for a projection screen). Also where are you in canada? anywhere near the Toronto area, Ontario? |
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| Duo |
Well, I do have a set of tubes with lenses and coolant intact out of an old zenith tv.
All three tubes have a nice hole burned out of the centers of their faces though, so kind of awful to try using them in a tv again. lol
I have no other equipment in this area, or parts.
P.S. I'm in western Canada, right on Vancouver Island. |
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| dangus |
Something to bear in mind with a front-projector is that light from the screen will reflect back off the walls and ceilings and audience and reduce the contrast. So, ideally the walls, ceilings, floor, furniture, and audience should all be painted or covered in flat black. RPTV screens are more directional, which reduces reflections from wall and ceiling, and they're usually tinted which also improves contrast.
You should definitely try it, though. If your source is an HTPC, you may be able to flip the screen in software. |
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| nickyj |
I was thinking the same thing. I have an old set and its starting to go a bit dim. I cleaned it all up and it got a lot better.
I'm a newbie so please forgive the question if it is moronic. But I was thinking......if the image can be converged on a smaller fresnel and then through a set of lenses it might just work.
I am not sure if it would be possible to change the light source(s) but all in all it seems like a very low cost solution if its possible of course.
The hardest part would be finding the tv's before the garbagemen.
(ps each of the three guns or whatever they are called are clean and do not show any evidence of burning or charring).
Any thoughts, suggestions, or comments. |
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| ancorp |
Why converge onto a fresnel? I think it will be much harder than to converge onto a bigger screen... Plus, the fresnel will probably add distortions, light loss, and ofcource shorten the focal lenght, I doubt anyone wants that, it already has to be so close to the screen!:)
The light sources are the actual tubes themselves. They are small, bright, black and white tv screens, with a color filter on each, green/red/blue. They can be replaced, but why, if they are in good condition?
...damn garbagemen, take the garbage, leave the projection tvs for the rest of us!;) |
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| Duo |
I'm thinking perhaps he's referring to the fresnel which is the screen itself. As far as I know, the screen of a rear projection tv is actually a style of fresnel.
As with the tubes, I've never seen a set with filters except on the green tube. Don't most use colored phosphorus instead? This would be more efficient. Perhaps I just haven't seen enough sets to find one with all B/W tubes and filters.
As far as brightness, when I work on a projection tv, I always clean the optics out (everything from the tubes to the screen), and then take an extremely light check on the screen voltages but alas, tubes, once worn, are only going to run brighter for so long... |
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| ancorp |
Yea, ive seen ones with only green filters are well, some with only red, (i have a set of lenses with 2 clear and one red).
I doubt that converging onto the big fresnel screen is a good idea either... Best way would just be to converge onto the projection screen directly.
Cleaning the optics regularily is a good idea. |
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| Skital |
I did this months ago with my 55" Toshiba 55X81 4:3 HDTV. I originally tried to go about 29 feet diagonal. lol. My wall could only hold about 20 feet of the image. It was absolutely MASSIVE. Unfortunetely, I was unable to converge the middle portion at this size. When I kept trying my tv would shut off.
So, I went to 10ft wide and converged it all the way and did the focus. I was using a regular dvd player through component inputs. I thought the image looked excellent considering I was using a 4:3 HDTV and no progressive scan dvd player.
I own an Infocus X1 and I was still impressed by my HDTVs picture (only viewed some tv and non progressive scan DVDs). I did direct comparisons between the two. The most noticeable improvements over my X1 was pitch black blacks, AWESOME high contrast ratio, 3D like picture depth and smooth pixel free picture.
I loved the look of the CRT. I think the focus could be a bit better though, because although I didn't realize it at the time, I discovered during the comparisons that my X1 was noticeably sharper.
The CRT made the X1's dark scenes look almost pathetic when I displayed the same dvd source.
If the CRT was as a bit sharper and if I was at least using a progressive scan player I think it would blow away the X1. I think a vertical squeeze would also help since I could use the full resolution of an anamorphic 16:9 DVD.
I think the focus may not be as good as a CRT front projector due to the extremely short throw lensesd on a RPTV. I was throwing a 10ft wide image from about 5-6 feet. I couldn't see scanlines with a non verticle squeezed DVD (a dvd missing 33% verticle resolution due to black bars) being played by a non progressive scan dvd player at 10ft wide even if I got close to the screen.
I had ideas to make turn a true widescreen HDTV set into a CRT front projector, because I thought a true 16:9 HDTV CRT front projector with brand new tubes, DVI/Component inputs, TV tuner, good 4:3 stretch modes (no 4:3 wear or burn this way), 60-100+ convergence points is much more valuable than the cost. I have found some good CRT sets like this for as low as $1000. A CRT front projector with the same specs would probably run you upto $10,000 or more.
The only things stopping me from doing this is that the focus isn't as good as a CRT front projector, and I think that's something that can only be improved by adding CRT front projection lenses to increase the projection distance. If you could find ones that would fit you could make ONE HELLUVA high contrast front projector with 1080i capability!
It was a fun project. I also did rear projection with it with pretty decent results. |
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| ancorp |
Nice:D.
The contrast really is amazing isint it? Was the image bright? compared to the x1, my guess is that the CRT was darker, but not necicerraly by alot. |
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| Skital |
The CRT was a tad dimmer than the X1, but still plenty bright at 10ft wide. At 29ft it was a bit dim compared to a 10ft image, but my eyes got used to it and the image appeared almost bright enough. Too bad I couldn't get it fully converged, because it still had a smooth film like appearance.
Cable tv even looked ok at 29ft (judging from the side I got converged). I don't know how that's possible, but it did. I guess since the focus isn't quite as sharp it smoothed the picture out a bit.
I found the 10ft wide image from a 480i dvd player on my CRT HDTV more enjoyable than my X1 at 10ft wide. The X1 was definitely sharper (which is the only really noticeable advantage it had) due to the short throw of the CRT, but the CRT was still smooth and filmlike with great contrast and blacks. The colors were much better on the CRT and made the colors on my X1 look totally unnatural and not very pleasing in comparison. It's strange, because the X1's colors looks fine to me when I'm not doing a head on comparison.
Another reason why my X1 appeared a lot sharper is because I run the highest sharpness setting, "Sharpest", due to my screen size. Most people use "sharper", because Sharpest is kind of artificial sharpness I guess. I say what the eyes sees the brain believe, so I leave on that setting to give me better percieved sharpness.
Another thing I loved about the CRT is that I could sit MUCH MUCH closer to it than I could with my X1. I could easily stand to watch from 10ft away easily at 10ft wide with the CRT. There's no way I could watch the X1 for long at 10ft wide when sitting just 10ft away. The pixels would be a bit too noticeable if I did (18-20ft would be more like it). I run my X1 at 8ft wide though, because 800X600 fixed pixels tends to make people in the background or in really wide shots not detailed enough.
I love that I can go over 8ft wide with the CRT, sit closer if I want and don't feel that I'm sacrificing a ton of picture quality like I do with a fixed pixel projector.
If I can find out if I can get some CRT front projection lenses that would fit on the widescreen Toshiba set I'm interested in I would buy it in a heartbeat and make myself a killer projector. |
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| ancorp |
| Nice. CRT all the Way!!!:D :D :D |
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| Skital |
Here's a screenshot of my CRT HDTV projected onto the wall. It's Finding Nemo (unfortunately, a bootleg copy that I was sent by a seller on Ebay when I thought I was buying the original) played with a regular DVD player through component hookups. The DVD player was set to 16:9, so the image is stretched to 4:3 (no anamorphic squeeze was used). It was only converged ok in part of the middle portion. I was unable to converge the left and right sides and some of the top and bottom, so they are way off.
Also, the camera I used is a one chip mini dv camcorder which is awful in low lighting (lots of grain), so I head to shoot with the shutter speed a 1/8th (in case you're not aware it is uses for real jerky movement and has a huge trail like effect; it adds a lot of grain and artifacts, but it brightens up the picture to get a screenshot that's somewhat useable and not overly dark).
The actual image is sharper, more detailed, smoother and flat-out better. It's the best my camcorder could do though.
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| ancorp |
| the brightness is very decent |
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