The Original page for this info can be found at   http://coinop.org/repair/Monitor_TubeSwap.aspx

Monitor Tube Swap Disclaimer: This information is provided as is. There may be errors in this information. You may use this information only if you agree that Minimalist, Inc. / Coinop.org, its employees, and noted authors will never be held responsible for any damage, injury, death, mayhem, etc. caused by errors in the information. When working with high voltage, never work alone and always follow safety precautions. Here's an example of a tube swap. This documents a successful tube swapping by James Sweet <jamessweet@hotmail.com>. Selecting images will show you a larger image. Other tubeswap pages: John in NH's Tube Swap Walkthru · Sanyo 20EZ (Nintendo) Tube Swap  Always DISCHARGE tubes before working on monitors.   1. This is the TV the tube came from. It is a good example of the type of set to look for, early to mid 80's manufacture, 19", not really worth anything even working so they're not hard to find for free when they're dead. 2. The monitor as received, the tube has severe phosphor burn and an intermittent heater to red cathode short. 3. This is the inside of the TV. 4. The purity rings on the TV tube, showing the markings made with black pen to enable them to be reinstalled in the exact position they were in. 5. Tube removed from the TV. Removed the purity rings, yoke, ground strap, degaussing coil and any other hardware. 6. The yoke from the monitor moved over to the TV tube and the original purity rings are reinstalled. 7. The monitor frame bolted up to the TV tube and the wiring connected. Any hardware such as a ground strap and degaussing coil that were on the monitor are moved to the new tube. 8. The now completely burn-free monitor. 9. The finished monitor. Once the swap is done it's necessary to align the yoke. It helps if you have a game that can produce solid red, green, and blue screens as well as a crosshatch. Set the monitor on something solid and power it up, you should have a picture but it will likely be crooked and the colors screwy. Degauss the tube, preferably with an external degaussing coil. Take care not to move the monitor while adjusting it, if you do you'll need to degauss it again or the earth's magnetic field will screw up your adjustment. Display a solid green screen and slide the yoke back until it hits the purity rings then slowly slide it forward until the color is uniform. Rotate it to get the raster level, then tighten the yoke clamp. Display solid blue and red screens and adjust the yoke as necessary to obtain good purity. Now display the crosshatch and tilt the front of the yoke up and down to adjust convergence in one direction and side to side for the other. When you have it as good as you can get it, install the rubber wedges and secure them with a blob of caulking or hot glue. Follow up by displaying color bars and adjust the RGB drive and bias controls on the neck board to obtain proper color balance. The manual for any color monitor should contain fairly detailed instructions for doing this.

A Minimalist web site. Copyright ©1994-2002 Minimalist. All rights reserved.

Additional Information (Arcadetreasure.com)

Be advised not all monitors are created equal. Meaning that swapping a CRT from a TV set to a monitor may not work out well in all cases. The big problem that will be encountered will be getting the dynamic convergence correct (non center area of screen) and the geometry.
This is because of differences in the Yoke/tube combination. Some of these problems can be corrected by adjustments on the chassis but not all game monitor chassis's are equipped with a full range of controls. Some have 3 position wires for example instead of a control. Some monitors have a very limited range of adjustment while others are very generous in what can be corrected. The alignment of the yoke will be critical in determining what your finished picture will look like. Besides the up and down tilt of the yoke, a certain amount of diagonal force to "warp" the yoke a bit, may be needed to correct errors in dynamic convergence. What does this mean. Simply, if the dynamic convergence is off, lines,characters and graphics will exhibit a color "ghosting" on the edge reflecting the error. How bad it is will be determined by how big the error is and what color is in error with relation to the graphics/text being displayed. For example if the game you are displaying shows a RED border line drawn around the screen and the error is in the red it would not be noticed. But if the border was white then you would see a red ghosting on the edge. The same thing would happen for white text, it would look like it has a red shadow.

Steve