DIY CRT-projector

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Henry Braithwai

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Joined 2002
tweaknmod-av.tk
#1
Hi!

I got a wild idea....

How about getting three really small (but preferably bright) B&W-monitors, sheet of red, green and blue filter and three projection lenses that are big enough to project the image of the small monitor's mentioned. Then we hook it up so that the R-signal goes to the monitor that is filtered with red filter, B-signal to blue and so on. Then we combine the images projected with these one color crt-projectors exactly like with "real CRT-projectors".
This would be a sophisticated version of those "put-a-freshnell-in-front-of-your-tv", but with at least 3 x brightness (might be even more because I think B&W monitors/TVs are brighter and at least the contrast is better, so the brightess could be even quite ok?) and by using real projection lenses the image quality depends on the monitors resolutions. The contrast and the color reproduction should ver much like on commercial crt's.
And in the end, isn't this the way the commercial crt's work in the end anyways?

Cheap way to check if there is any reason to this would be obtaining three B&W monitors (someone of you must have access to some warehouse to loan few for testing? I think they use monitors and tv's that would be ok for this test in about all superstores and so on?) and three freshnell page magnifyiers and those filters. If the brightness is ok and it's somewhat easy to combine the images then it might be worth the effor to hunt down those monitors small enough to be used with some projection lenses!

Regards
HB
 
#3
Having worked on the design of CRT projectors in the past, what you are looking at doing is very very difficult. Converging the image from the three CRTS requires fairly sophisticated circuitry to do well. Simple mechanical matching is simply not enough, not even close. You can purchase the proper colored CRTS. That would give you much higher brightness then filtering 2/3 or more of the light out of a B&W CRT. Projection CRTs are also designed to be driven much much harder and hence much brighter.

You can pick up surplus 7" projection lenses pretty easily.

Not saying it can't be done, just saying that there are likely much easier things that can be done that are likely to yield better results.
 
#5
Please dont try this. For one thing if you ever get it to work, the resolution is going to be junk....remember that a tv is only 480i resolution i believe.....not even VGA. All commercial crt projectors...even the old ones can handle VGA...and most higher. The cost is going to be extreme because you are buying 3 televisions, three sets of lenses....wich by the way arent going to be well matched for the television crts you choose (unlike the commercial lens/crt combination). Next the brightness is going to be awful dim. Look at how much light/wattage a 5 inch bw tv puts out....not enough in my opinion. Last.....the convergence is going to be next to impossible to achieve....mechanical allgnment is simply not enough.....you will need to reposition where on the phosphor fase the "center" is on each of the outside crt's so that they all align to one point on the projected image.....while it can be done, you'll be playing with way too much HV that wasnt designed to be modified (and you'll have to modify it each time you move the projector).

While it would be a noble effort, you will end up with a complete failure, an image that is terribly dim, and a lot of investment compared to a cheap crt projector that you can buy with better resolution.

Sorry
 
#6
Very unlikely that a cheap and small B&W TV will be a true 480i. I'm sure it'd be MUCH less, like 250 lines or something. That's garbage. But eebasist was saying, 480i is the absolute best it could be (which it won't) and you'll have no PC inputs.
 
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