On Tue, 16 Apr 2002, Douglas H. Quebbeman wrote: 5.23 How to adjust MegaPixel Display brightness and focus? brightness, MegaPixel focus, MegaPixel Adjust it using the following information. From: Charles William Swiger I have adjusted several monitors with no problems, but make sure you know what you are doing before opening anything. I expressly disclaim responsibility for any ill results that may occur. In order to adjust NeXT's MegaPixel display (called 'the monitor' hereafter), you'll need (a) the NeXTtool (or a 3mm Allen wrench), (b) a plastic adjustment tool (preferred) or a thin bladed screwdriver, and possibly (c) a Phillips-head screwdriver. (NB: A similar procedure will work for color monitors, but you should either know what you're doing or you'll probably be better off letting a pro deal with it.) Turn off the computer. Disconnect all cables to the monitor. Look at the back of the monitor. There will be 4 screws there; use the NeXTtool (or Allen wrench) to remove them. Remove the plastic back of the monitor and put it out of your way. Reconnect the cables and turn the computer back on. As the machine powers up, examine the back of the monitor. You'll see a metallic box (usually silver, though some are black) surrounding the monitor's vitals. This protects you against the dangerous voltages inside, and also insulates the monitor from electromagnetic noise. On the back of this box are several holes for performing adjustments. There are two focus controls (labeled 'focus' and 'dynamic focus'), a brightness control (labeled 'brightness' or possibly 'black level') and several others that adjust various things like screen size and position. Depending on the exact placement of the controls on the circuit board of your specific monitor, some of these controls may be difficult (or impossible) to adjust from the back. If this is the case, I will describe what's necessary below. Otherwise, adjust the appropriate controls using either an adjustment tool or a screwdriver. Be warned that a screwdriver probably will cause some interesting video effects when it enters the case. Ignore this the best you can, or find a plastic adjustment tool, which is what you *really* should be using anyway. Using a flashlight will help you see into the hole so that you can align the business end of the tool correctly. Focus and position controls are fairly obvious. Adjust them slowly until you're happy with the results. Don't muck with anything you don't need to; the factory settings are usually pretty decent. To correctly adjust the brightness, follow this procedure: Turn the brightness of the monitor all the way down using the keyboard. Adjust the brightness control on the back of the monitor until a barely noticeable picture forms. Then turn the brightness down a little so this picture disappears completely. Check that you can get adequate brightness by using the keyboard to brighten the screen. If the display isn't bright enough, adjust the brightness control on the rear of the monitor high enough so that the monitor display is adequate. Note that you won't be able to dim the screen completely from the keyboard...sorry. Once you're finished, shut down the computer, take off the cables, reattach the back of the monitor, and reconnect the cables. You're done. If the control you need to adjust proves to be difficult, you may need to enter the metal case. This happened on one monitor's focus control and another's brightness. WARNING: THE VOLTAGES INSIDE THE MONITOR'S CASE ARE VERY DANGEROUS, EVEN WHEN THE MONITOR IS OFF. BE VERY CAREFUL, OR YOU CAN SERIOUSLY INJURE OR EVEN KILL YOURSELF. DO NOT PERFORM THE NEXT INSTRUCTIONS UNLESS YOU ARE CONFIDENT THAT YOU KNOW WHAT YOU ARE DOING. You'll have to power off the computer again, and disconnect the cables. Looking at the monitor from the back, notice a section of metallic shielding on the right side of the metal box that extends to the picture tube. This is where the flyback transformer is connected. It shields a wire that is charged to about 25,000 V. WARNING: DO NOT TOUCH THIS WIRE, IT CAN SHOCK YOU THROUGH ITS INSULATION. Being very careful of this, remove the metal case by unscrewing the Philip's head screws that hold the case on. Don't touch the screws that hold the picture tube into the front of the monitor's case. Once you've gotten the metal box off, reconnect the cables. Figure out what control you're going to adjust, and make sure that you can do so without touching anything else inside. Again, *watch out* for the wire that connects to the picture tube on the right side. Power up the computer. I recommend that you use only one hand to make the adjustment, and that your other hand be placed in your pocket (or similar equivalent, if you're wearing clothes lacking pockets). This precaution reduces the chances that you'll make a short circuit between one hand, your heart, and the other hand --- a good idea. Perform the necessary adjustment(s), being very careful not to touch anything inside. Then shut down and reassemble the monitor, following the directions given above. Hopefully, these instructions will prove useful. Once again, please be very careful...I don't want your death and/or injury on my conscience (or a lawsuit, for that matter, either :-) 5.44 What makes aged NeXT monitors dim? monitor, dim The cause of the dimming monitors is the CRT cathode wearing out. The most common type of CRT (and the type used in most NeXT monochrome monitors and all of the NeXT color monitors) uses what is called an oxide cathode. A thin coating of oxide is deposited on the cathode to allow the electronics which form the picture to get off the cathode easily. The oxide gradually boils off the cathode itself, and when the oxide is gone, the CRT goes dim. Typically, the oxide will last from 10,000 to 20,000 power on hours (screen savers don't help the cathode, they only prevent phosphor aging). Unfortunately, the black monochrome monitors fall into the short end of the life range thanks to Toshiba who made the CRT's. The aging is more noticeable in Unix machines because they tend to be left on. Note that there are about 8,000 hours in a year. If you leave your monitor on all the time, all oxide type CRTs will be dim in three years. The other type of CRT cathode is the I-cathode or dispenser type. This type of cathode is porous and continually brings new activation material to the surface. Its lifetime is 40,000 hours or more. The last of the NeXT monochrome monitors (N4000B) used this type of CRT and they don't go dim. There aren't many of that type around because NeXT quit the hardware business after producing only a few thousand. If you can get an N4000B monitor, you won't ever have to worry about a dim monitor. Many manufacturers are going to dispenser cathode type CRTs in their monitors with Panasonic leading the way. The best advice is to turn off the monitor when not in use. If that is impractical, try to purchase one with the long life cathode. Spherical Solutions (smg(a)orb.com) has a supply of new N4000B long life monitors for sale in either ADB or non-ADB configurations. If you need to repair or replace a monochrome monitor, that is by far the best type to use. If you read this far, you probably know more than you ever wanted to about CRT aging, but I hope this helps. HTH ok r.

On Tue, 16 Apr 2002, Douglas H. Quebbeman wrote: Phosphors do lose efficiency but I dont think that is the main problem. I think mainly the cathode loses emission. This can temporarily be improved by CRT rejuvinators or raising the heater voltage (I'm old enough to remember the old cylindrical autotranformer picture tube brightenters that you stacked on the old B-W TV CRTS: they basically raised the heater voltage a little bit, squeezing a little more life out of the CRT) Peter Wallace