BonMul answers: I don’t know. its difficult to guess. Your best bet is to remove the screen and project it on a wall and see if you get bigger picture in focus.

Modifying a lot of what I said above…

This CAN be done with CRT tech, but a lot more things have to be taken into consideration. This DOES explain why the brightness is still usable, and why the focusing stays roughly the same, with such a small, single aperture…

Mr Bob

“The image comes out of the lens and is reflected off of the mirror which then is displayed on the screen. The image only has to be in focus where it hits the mirror for the picture to be clear on the screen. Really the screen, or whatever you are projecting it on could be at any distance without losing clarity as long as the lens and mirror don’t change.”

Sorry Charlie, gotta diagree with you there. The mirror has nothing to do with the focusing. The focusing would be the same whether there were a mirror there or not - the lens to screen throw distance would be identical in both scenarios.

Where the mirror is, everything is out of focus at that part of the light path.

The lens to screen throw distance is what is fine-tuned by the lenses, which involves loosening the wingnut, refocusing and then tightening it again.

Again, I recommend the Cantilever Technique for the nth degree of precision in optical/mechanical focusing.

What didn’t change in focusing with this project was the electrostatic focusing of the focus trimpots of the focus block.

The optical/mechanical focusing would be WAY off once the throw distance had changed by several feet as in this instance, and definitely need to be refcoused. Unless it was out of focus in the first place and adding a few feet of throw distance put it exactly in focus.

But being out of focus OOB is rarely the case with a Sony CRT RPTV. Sony’s the only brand I can say that about, after more then 20 years as a professional calibrator.

Mr Bob
http://www.imageperfection.com

If you leave it as it is, only most of the available CRT face area is being used/viewed. Shimming it upward where it’s mounted in the RPTV chassis would push the image forward and out of the optical cavity, and allow the entire usable surface of each CRT face to be utilized, only limited by the positioning of the image on each CRT face. On this kind of set, you can’t even think of changing the actual angle of the CRTs themselves. To do so could expose you to all sorts of scheimpflug considerations, which affect how completely the focus is across the CRT face in all directions.

Mr Bob

Wow, that some technical info!! Thanks for stopping by.

The brightness level is not that bad, Its watchable with a florescent light on. When I turn off all the lights, the brightness is awesome.

I agree with over scan advantage; But I have multiple sources connected, like media center PC that over scans, but I adjust the screen for PC, TV picture is under scanned. So have to find a middle ground.

They don’t have it anymore on HTDepot.com. But if I were to do it again, I would not buy a screen. I would buy rear projection cloth on eBay and simply staple it to the wooden frame. It would have cost just 50 bucks or less.

There are 2 focusses: electrostatic at the focus block, and mechanical at the lenses, secured by the wingnuts.

The electrostatic would not change. However, the mechanical would, and greatly at that distance. I would recommend the Cantilever technique for getting the optical/mechanical right again.

The overall light level would be a factor, because the bigger the screen, the more dispersed and thus lower the light level becomes. With the 7″ guns used in this RPTV, the light level could be reduced by half, with double the screen size. 9″ guns, like used in the Mit 73″ and one of the Mit 65″ models and all the older Zenith and Philips/Marantz 65″ models, would deliver 9/7 more light output.

The aiming of the outer 2 guns might also be an issue, tho if it works, it works! The centering on the guns themselves on the CRT faces would have to be readjusted at the very least, tho. Found that when I shimmed my 73″ Mit up towards the mirror by 1.5″, exposing lots more of the CRT face to the screens than before.

Speaking of which, this gives you the ultimate opportunity for overscan reduction WITHOUT having to reduce your height and width inside the service menu, and all the resultant corrections that need to be made when reducing overscan that way. This way you can keep your picture where it is on your CRT faces, with only minor mopup needed, compared to the major conniptions of the sm-only way of doing o’scan redux.

Haven’t read this whole article, but you would definitely want to be using the same TYPE of fresnel/lenticular sandwich as is used in all CRT RPTV tech, to be sure and capture its light-gathering potential. Just a frosted screen would not gather and direct the beam properly like the classic f/l sandwich does, you’d have way more scatter than in the classic RPTV sandwich, which DOES beam the picture right at you, maximizing your light levels. I find RPTVs have at least double the light levels that front projection has, shooting at a semi-reflective screen, which disburses the light in all directions.

Awesome project!

Mr Bob
http://www.imageperfection.com