Computers are useless without a monitor. You can't surf the Net or see what you typed on the keyboard. It's a good thing that computer monitors are virtually trouble free. Besides checking to see if it's plugged in and making a few adjustments there's little you can do to fix it without specialized help. Even so, let's take a look at how they work and how to tackle something you can fix, the monitor fuse.

How Does It Work?

Components of a typical computer monitor.

A computer monitor, sister to the television monitor, displays information from a computer on a screen. The monitor uses digital values sent by a computer processor to create a stream of electrons that light up phosphors on the inside of the screen. The signals are in each of the three primary colors, combined into various color signals that seem to move across the screen. Portable computers use a screen made up of liquid crystal display (LCD) cells instead of phosphors. Computer monitors receive their signal from a monitor cable from the computer and their power from a separate electrical cord.

What Can Go Wrong?

Computer monitor problems are not always problems with the monitor. Testing of the monitor must be done with the computer . The monitor may not come on. The image on the screen may not be clear and bright.

How Can I Identify the Problem?

If the monitor does not come on, make sure there is power to the electrical receptacle . Check the electrical cord . Check the connections between the monitor and the computer  and make sure the computer is on. Test the line fuse  (see below).

Interior of a computer monitor. Identify but don't touch the power supply.

If the image on the screen is not clear and bright, check your owner's manual for instructions on adjusting the monitor. Typically there are adjustment buttons on the monitor face below the screen.

What Parts, Materials, and Tools Do I Need?

Replacement cables and fuses are available from the manufacturer as well as from local computer shops. Tools you may need to access, test, and fix a computer monitor include these:

• Screwdrivers
• Multimeter

What Are the Steps to Fixing It?

Fix-It Tip

A computer monitor gets its instructions from a video controller card in the computer. The card may be an add-on expansion card or it may be built into the main circuit board, called the motherboard. If it is a separate card, you may need to open the computer and make sure the card is firmly connected. Also check the flat data cable that runs between the video card and the motherboard, if so equipped.

Locate, remove, and test the line fuse, typically located near the power cord entry.

Test and replace a monitor fuse:

1. Disconnect the monitor from the electrical receptacle and from the computer processor.
2. Lay the monitor on a padded surface and remove the housing screws (some may be under pop-out tabs).
3. Slide the rear housing off.
4. Locate the line fuse typically near the power cord entrance. Remove the fuse from its holder and test it with a multimeter. Replace the fuse if it is faulty.

Caution!

For safety, follow the manufacturer's instructions in the owner's manual to discharge the video tube before working near it. In most cases this means using jumper wires to connect a 10,000-ohm resistor between the chassis ground or common ground and a screwdriver, and shorting the high-voltage lead by inserting the screwdriver under the suction cup.