- The most common culprit is a loose cable. Check the connection on the back of the monitor and on the back of the computer. On each side of the cable's connector is a screw. Some of them can only be tightened with a Phillips screwdriver, but most are adjustable by hand. It doesn't need to be screwed in tight--just tight enough to keep it from getting loose again. Sometimes the connector isn't flush against the port. Therefore, it is not advisable to tighten one screw all the way because the other screw can't get in. Tighten each side a little bit at a time until it feels secure.
- Proper case air flow prevents damage to your display components.
Other times, the cables will be fine but the image is still distorted. In this case, you may have a more serious problem. One cause of distortion is damaged hardware. The inside of a computer case produces a lot of heat. If there gets to be too much heat, components in the case can melt. When they melt, the only way to fix it is to repair the component altogether. Ensure that the case has reliable air flow to avoid this problem. The amount of cool air coming in from the front needs to equal the amount of hot air coming out the back. Too many fans blowing in, or too many blowing out, will create an imbalance.
- Surge protectors can prevent electrical damage.
Another cause of damaged hardware is a power surge. Sometimes an electrical storm causes this--a lightning bolt hitting your residence and the electricity from the bolt not getting fully transferred into the ground. Such storms can also knock out your electricity, causing a blackout or brownout (which is partial loss of power). When the power company repairs this problem, there may be surge as well when the damaged parts of its grid get repaired and come back on line.
For this reason, you will want to have your computer plugged into a surge protector. Not all protectors are made equal; the cheaper ones are only designed to handle one surge, then they have to be replaced. A computer connected to a phone line can also be damaged when a lightning bolt hits a telephone pole. This is why many surge protectors also have a phone jack.
- It's possible that the monitor (or the computer) has been physically damaged. Visually inspect the monitor's case and the internals of the computer's case for loose or broken components. Sometimes the damage is not visible; consult a repair technician or the manufacturer if your products are still under warranty.