Things You'll Need:
- Screwdrivers (Phillips, Allen and Torx)
- Ohmmeter/multimeter
- On-screen keyboard
- 30-gauge insulated wire (wire-wrap wire)
- Conductive pen
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Step 1
Open a computer program where you can diagnose the keyboard's problems. Go to "All Programs," "Accessories," "Accessibility," "On-Screen Keyboard" in the Windows Start menu. Or go to "International Preferences" on a Mac's System Preferences menu and check off "Keyboard Viewer" from the Flag menu.
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Step 2
Press each key on the keyboard one by one and watch for that key to turn gray on the on-screen keyboard.
Mark down all the keys that don't work. Usually, the bad keys will be in a pattern, indicating a keyboard matrix failure. -
Step 3
Remove the computer's outer case by removing the screws on the underside and lifting the keyboard out of the base. Disconnect the ribbons connecting the keyboard assembly to the encoder circuit by pulling straight back on the tabs or opening the latch. Remove the screws holding the encoder board to reach the board's solder side.
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Step 1
Make a jumper wire by cutting 6 to 8 inches of wire-wrap wire, stripping a small piece of insulation off at each end and curving the wire into a hook.
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Step 2
Hook the wire onto Pin One of one connector and drag the other wire end across each pin on the other connector. Look for a flash on the on-screen keyboard. No flashes means a possible problem with the line on the hooked connector.
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Step 3
Repeat this for each pin in the first connector (the one you're hooking the wire to). Test the other connector in the same manner.
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Step 4
Mark down the number of the hooked pin when no flash appears, especially when testing the pin related to the keys you know work. When all the bad keys turn up a bad connection on one particular line, it usually means a problem in the matrix that you can correct.
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Step 1
Disassemble the keyboard assembly. Remove the screws on the metal plate and lift off the plate to reveal the keyboard matrix of the keyboard. Lift the matrix sheets off of the keys, but don't separate the sheets where they are connected. Carefully store all the small caps with each key and the screws that held the plate.
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Step 2
Trace a path from the suspect ribbon connector until you reach one of the bad keys. The matrix will likely be discolored in the trace area between two or more bad keys.
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Step 3
Measure the resistance with an ohmmeter between two known good key points, which should only be a few ohms. Measure the resistance between a bad key point and its adjacent good key point. If the trace is bad, the resistance is much higher.
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Step 4
Clean the bad area lightly with a clean, wet cotton swab. Wait for the space to dry, and remeasure the trace just outside the bad spot. It must be repaired if you still read a high ohm level.
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Step 5
Dab ink from a conductive pen along the trace over the problem area. Dab the ink lightly across the trace, but don't draw across it. Wait 10 minutes for the ink to dry, keeping the other matrix sheets away from the patched area.
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Step 6
Test the problem area again, measuring on the original traces before and after the ink patch. A small measure of ohms means the repairs worked.
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Step 7
Reassemble the keyboard. Place the flexible caps back at each key position underneath the keys. Place the matrix sheets back in the proper position, linking the holes in the sheets with the raised plastic keys on the key assembly. Screw the backplate on over the matrix sheets. Reattach the assembly to the encoder board and then the outer case.
