How to adjust the screen drive on CRT projection TVs.

When your projection TV is getting darker and darker what do you do?

You need to turn up the screen drive on the CRTs.

As the CRTs age the elements get coated with oxide and do not put out the same amount of light. As the light output diminishes you turn up the setting on the menu but eventually there is no more adjustment.This is because the on screen menus are limited by the settings on the focus divider block.

Before turning the set off set the brightness and contrast to their center position in the on screen menu. Now turn the set off.

The next thing you need to do is unplug the set.

With the power removed remove the lower back cover. Usually this requires removing the screws marked with an arrow. The process should be obvious.

Once the back is removed locate the focus/divider block. It will be a small (4 x 4 inch) unit mounted to the frame (normally) and have wires coming from the high voltage section. It is almost always mounted on the right side of the unit on the frame holding the three CRTs.

The wires plugged into the unit will be large, soft rubber and red in color. There should be three wires. They should attach to the flyback which is the high voltage transformer. The flyback (high voltage transformer) will be mounted on the power/high voltage board and is almost always on the right side of the chassis.

The flyback generally is a squarish box near the rear of the unit and on the same board as the low voltage power supply. It may have a round cylinder in the middle, or not, but it will have a square laminated steel bar running through the middle of it. It will also be where the wires from the focus divider block, mentioned previously, terminate.

To set the drives you will need to power the unit up. Be very careful and try to keep one hand in your pocket at all times. There are lethal voltages inside this unit and if you do not feel confident working on it stop now.

When the unit has warmed up try to tune it to a black and white channel or a public information channel. If neither is available find a channel with alot of black and white in it. This is necessary to get the drives set properly.

Looking at the rear of the focus/divider block you should see 6 shafts. The top three are for focus. Do not touch them. The bottom three are the ones you want to change.

They should be left to right, red, green, blue guns. Turn each one in turn up until you see the color in the black of the picture then turn slightly down (until the color rastor disappears). Do each in turn until all are maximized.
They will be maximized and set correctly when the raster is just on the verge of being visible, but not visible.

The brightness should now be as good as it gets. You may need to turn up the screen menu drives for brightness or contrast to get the picture you were looking for.

Thanks for using FixYa and for the excellent rating.

hardrocko