Definitive CRT Projector Setup Guide

Here, humbly is a guide for first time projector owners to get the most out of their projector. Hey, veteran CRT owners might get something out of this too! Feel free to critique like crazy if I’m missing some steps (quite possible) and email me with comments. I’ve based this on the NEC XG, but of course the principles can be applied to any CRT projector, entry level or high end, ES or EM focusing.

The following topic are described in detail with plenty of pictures showing you exactly what to adjust:

• Raster/tube face setup
• Optical focusing
• Scheimpflug adjustments
• Electronic focusing
• Astigmatism control
• Lens toe-in
• Electronic astig adjustment
• Electronic focus
• Tilt
• Bow
• Amplitude
• Linearity
• Linearity balance controls
• Keystone
• Point adjustment
• Later model point convergence software
  

Raster/tube face setup

This is one of the most misunderstood areas of CRT projector setup. Here’s some basics:

All CRT tubes come in a 4:3 format rather than a 16:9 configuration. Regardless of whether you project in a 4:3 format or a widescreen one, you want to use as much of the tube face as possible to maximize tube life. By using as much of the tube face as possible, you’ll also increase the maximum resolution out of the tube as you’re spreading the image out over a larger area of the tube face.

Note that the internal test pattern of the projector will always be slightly larger than the projected image. This is purposely done so that the test pattern will overshoot the screen slightly. By overshooting the screen, you’ll be ensured perfect convergence right to the edge of the screen and past it. When the projected image then fills the screen, it will be perfectly converged.

The idea is to maximize the phosphor area of the tube without overshooting the tube face. There is cooling fluid between the glass face that you see on the tube and the actual phosphor behind it. If you overshoot the tube face, you’re causing the electron beam to shoot off the phosphor onto the edge of the glass that has no cooling fluid on it, and the tube edge can overheat and implode. Shown below are some good and bad examples of tube phosphor use.

Good- the raster/test pattern is centered on the tube face, there is a visible margin between the edge of the tube and the test pattern. Maximum use is made of the tube face.

In a 16:9 (widescreen) configuration, less of the phosphor face is used, as the picture will be projected in widescreen mode as shown below. While the below image shows the test pattern being very close to the tube edges, the projected video image will be smaller (less width and height), so a margin of safety is still being used in this setup. Since you’re (hopefully) not going to be projecting the test pattern for hours upon hours, there’s no chance of a tube implosion with the test pattern running right to the edge of the tube in setup mode.

The NEC manual is somewhat flawed in that it tells you to mount the projector back a little more than what is ideal for maximum tube face use. The picture below shows a test pattern with a wide margin between the edge of the pattern and the edge of the tube. You’ll end up using less phosphor area which will result in shortened tube life and lower overall resolution.

You also want the test pattern centered on the face of the tube. Below are examples of rasters/test patterns that are shifted off center on the tube face. This will result in convergence drift and uneven tube wear.

Image shifted too far to the right on the tube face:

Image shifted too far up on the tube face and to the left:

The NEC XG chassis specifically has two sets of raster shift adjustments. The fine adjustment is the ‘position’ button on the remote. The coarse adjustments are done in the ‘ref adjust’ settings in the ‘adjust’ mode. The ‘raster centering’ mode will allow you to perfectly center the test pattern on each tube. While adjusting the ‘ref adjust’, make sure the ‘position’ settings are at 0,0. This will then allow you to fine tune the raster shift during the final adjustments while maintaining the overall centering of the coarse ‘ref adjust’ settings.

The height and width controls of the set will adjust how much of the tube face you’re using with both the test pattern and the video image. You’ll run out of width before you run out of height on the tube face, so maximize the width used without overshooting the tube face. The exact height can be dialed in during the geometry setup of the green tube.

Once your raster is centered on each tube, you can now check your throw distance to the screen. I normally recommend that you set your projector on the floor before mounting it to the ceiling if that’s where the projector will be located. By temporarily floor mounting the set, you can move the projector back and forth a few inches to adjust the throw distance, then measure your throw distance and mark the ceiling appropriately to mount the bracket.

Typically I recommend that the test pattern overshoots the screen left to right by about 2-3” on each side. The actual video image should then fill the screen, and the width/amplitude control of the set should be able to compensate for slight adjustments needed to fill the screen.

Focusing

There are two distinct parts to focusing a CRT projector: The optical focusing, which is the relationship of the lens to the tube face and the screen, and the electronic focusing of the electron beam/image on the tube face. Both the optical and electronic focusing must be set perfectly in order to get a sharply focused image on the screen.

Optical Focusing

Most projectors have lenses similar to the ones on the NEC. Each lens has two adjustments to optically focus the tubes, the back wingnut or knob that is the coarse/overall focusing, and the front adjustment that is for corner focusing only.

Loosen the back wingnut and grasp the front barrel of the lens to rotate the lens. Set the lens for the best focusing in the middle of the screen and tighten the wingnut. Then loosen the front wingnut and again rotate the front barrel Tighten the wingnut once the corner focus is set.

Here is a picture of the coarse optical focus misadjusted. The whole screen is out of focus. If you put on sunglasses and look through the lens at the tube face, it should be in focus.

Here’s a picture of the corner focus wingnut being out of adjustment. Note that the center of the image is in focus, but the edges are blurry.