I have an idea.....:scratch2:
http://images.google.ca/imgres?imgurl=http://www.users.qwest.net/~ptaylor/Electronics/TinyCRT3.jpg&imgrefurl=http://www.ccs.neu.edu/home/bchafy/tiny/tinyterminal.html&usg=__lMcIJQPP13UbGuwzpGYIBsZCY-U=&h=960&w=1280&sz=321&hl=en&start=1&um=1&tbnid=JqOXTHCmF6nX4M:&tbnh=113&tbnw=150&prev=/images%3Fq%3Dveiwfinder%2Bcrt%26um%3D1%26hl%3Den%2 6client%3Dfirefox-a%26rls%3Dorg.mozilla:en-US:official%26sa%3DN
On that page are pictures of viewfinders from camcorders containing a small crt.

I want to use 3 of these and colored gel/or lenses to create a mini CRT projector. Not for any real purpose. Just to say that I may have the Worlds smallest CRT projector.

It would use a single lense with a pre set distance it would work at. The convergence would be purely mechanical. And probably poor but. What do you expect.

The one real problem I can think of. Is getting each CRT to represent a color.(electronically)
This most likely will involve either a board from another projector or maybe even a TV. This is why I need your help. I'm not too sure of what kind of board I'll need or if it even exists. In any way shape or form.

Please tell me if I should just give up on this or if there is hope!
Thanks
Rudy

P.S. I know projectors aren't the Topic of this forum, but I know you are all very knowledgeable and will most likely know how to get this done

The one real problem I can think of. Is getting each CRT to represent a color.(electronically)
This most likely will involve either a board from another projector or maybe even a TV. This is why I need your help. I'm not too sure of what kind of board I'll need or if it even exists. In any way shape or form.



The NTSC decoder circuit (chip?) will likely have a red video out, green and blue. Easily tapped off a TV board. 3 emitter follower circuits to allow these red, green and blue video signals to drive 75 ohm loads.

Biggest problem would be that these tiny CRTs will not produce much light, and you'd need a totally blacked out room at night to have a prayer of seeing anything on the projector screen.

He he he. I knew Tv's had the stuff to get three sep. colors but I just didn't know how.
I still sort of don't completely understand. The way you exactly put it Waise. (I'm only 18) But trust me. I wrap my head around things fast. Just a little more detail. Please :)

And yes. These wee little CRT's would be dreadfully dim. I don't even know if it would really work. But according to some one who has actually played with these. He thinks you might be able to get a 5 inch screen going In a Pitch Black Room

So I figure. If you got three going at once. A 5 inch screen should be veiwable.

And thanks for the Input Waise. I've seen some of your stuff and you are DEF very knowledgeable :thmbsp:

Also If this even worked....Slightly(doesnt have to be HD!) I would be very impressed. And have a very interesting peice to show.

Rudy-

As WA2ISE said, you would need the three separate color signals for your three CRTs, and the easiest way to get them would be to hack apart a small color TV. To do this project, you should read a lot about how color TV signals are received and sent to CRTs, and compare all of that to the similar details of how a black-and-white CRT TV works. The big nightmare you would have to work out, to make a three-CRT projector, would be positioning everything to get any kind of viewable image at all. It may be impossible with a lens set away from the CRTs. As an additional note, if you did not already know this, in the 80's there were kits for sale to "turn your TV into a big-screen projector". They essentially put a big round lens in front of a 13" color TV that had its contrast and brightness turned way up, and made a very dim but viewable picture in a dark room. You had to switch the yoke wires to the CRT so its picture was upside down (then the lens flipped it correct again).

I have heard about people doing the CRT Projector with a single 13" CRT.
Apparently yes it is dim and the screen will not last to to long run under those conditions.

I know that each gun. Red Green and Blue. Gets the correct voltage/intensity according to where the scan is at that point.

I wanted to know if there was a simple way using the inards of a color TV to get these three seperate colours into an actual video signal. That you could per say hook up to another TV just to watch the Red from a color signal. (or green or blue w/e) This would make the project much more simple. Than splicing a color board to the three CRTs existing circuitry.

And yes the placing of lenses and the crts would be THE HARDEST PART. I might look into prism focusing to get it done. But you let me worry about that part.

But are you telling me that what I just described is Possible though??
If so I will begin collecting parts for this.
Thanks
Rudy


P.S. In my first post I said " I'm not too sure of what kind of board I'll need or if it even exists. In any way shape or form."
I worded that wrong. I know Tv's obviously seperate the three colors. I just did not know if this board put out an actual video signal out that you could hook up to a Tv's AV in and get just a red picture.(or green blue w/e)

>>> I just did not know if this board put out an actual video signal out that you could hook up to a Tv's AV in and get just a red picture.(or green blue w/e)

The signals that comes out of the colour decoder chip (separate RGB) MAY not be compatible with composite NTSC, because these RGB signals are designed to drive the CRT, and may not maintain the correct synch pulses anymore for composite compatibility. Depends very much in the particular set & its design though.
If you have the board, see what chip is on it & download that chip's datasheet - it will tell you all about the wqaveforms present.

Many DVD players have separate RGB outputs that you could experiment with, but the synch pulses are often only present in the green signal.

I think brightness will be a BIG problem - those tiny tubes are made to be viewed about 1" from your eye.

Ive done this before. using old viewfinders and with the same lenses made a mini-CRT projector.

it will work ok, if you use a NTSC Decoder circuit. youll get a R, G, B, and H/V sync. that you can mix together and get the composite sync needed to drive the CRT view finders. BUT on some cases you may need those H/V sync lines depending on the viewfinder. Cliff Benham will be able to clue you in on where to get an NTSC decoder module. (as you need this to make a homebrew color-wheel system).

your next problem is convergence. youll never have convergence unless you design your own circuit. In my case, i used a rather large analog convergence board, and took the H/V sync gate pulses into the board, and outputted this into makeshift coils wrapped around the current yokes.

it worked ok, but you could never get it perfect. (obviously).

You could use a prism block from a scrapped LCD projector (i might have one actually). but the viewfinders will need matched. as obviously you can have slight errors in the geometry of one of the CRTs, can throw your alignment off on that CRTs color. so you gotta have width/linerity/hight controls for each individual CRT to do this the easy way.

then you still have your pincussion and keystoning issues that you wont be able to overcome unless you modified the circuitry for it. i dont know exactly how yet...

Also you need to modifiy the circuit a little bit to try and see if you can kick it up about 1kv. this will help tremendously for brightness. you cant go much higher than this unless you change flybacks. and even then youll have a problem with arcing/cracking the CRT and xray.

but modifiying the HVreg circuit you could get maybe an extra 500 to 1kv.

Aww man so it's been done already.

Mbates, you don't have any pictures of this PJ you could share do you? I am very interested in seeing this PJ you've built. And an image of it playing maybe.

I am in no Rush to complete this project. As I have very few parts to work with. And will need to collect for a while.

well i did this when i was about 14 or 15, and ive moved since then. that sucker is long since gone. lol. i wish i would ahve kept it.