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Step 6Test the Encoder Board.
Using the jumper wire from the previous step, we will test the Keyboard Encoder. If this test is successful, our chances of successfully repairing the keyboard just went through the roof. A failure here would normally mean the keyboard's a doorstop.
Examine the two connectors. One will be smaller than the other. Since the failing keys are positioned vertically from each other, the failing line will likely be one from the larger connector. If the failed keys had been across the keyboard, we'd look for the bad line on the smaller connector. We will use the hook on the suspect connector and use the other to test it.
Using one hand, hook the hooked end of the jumper onto pin one (it should be marked) and hold it reasonably tight. Too tight, we'll straigten the wire and have to fix it again. Too loose and it falls off the pin.
Now carefully drag the other wire across each side of the other connectors pins, watching for flashes in the Screen Keyboard. Pay particular attention to the failed keys.
If you see any flashes at all, that line on the hooked connector is good. If it turns on the Caps Lock key, touch that pin again to turn it off. This way we avoid shorting out the Cap Lock LED.
Proceed to move the hook to pin number 2 and retest. Continue with each pin of the suspect connector. If they all pass but none of your bad keys appear to be pressed, test again then reverse your wire and test the other connector the same way.
If any of the lines produce no reaction at all when jumped; Note that line. It may not be a problem, but a ground line for the assembly. But then is could be our entire problem too.
When you do see one or more of our problem keys appear during this test, mark down the number of the hooked pin that it appeared on. Recheck that line to verify that all of the problem keys appear when jumpered with different lines on the other connector.
In this case, the problem keys all appeared when testing line 18 (of 19) on the large connector. This is good! It means a lot more work, but the problem is in the matrix itself and probably fixable.
If the bad keys did not appear while testing either connector than the Encoder chip is bad. We could carefully examine that all the traces on the Encoder Board are intact and repair any break we find. Then test again. We're not going to go into detail of that rare problem because it isn't the situation here.
Examine the two connectors. One will be smaller than the other. Since the failing keys are positioned vertically from each other, the failing line will likely be one from the larger connector. If the failed keys had been across the keyboard, we'd look for the bad line on the smaller connector. We will use the hook on the suspect connector and use the other to test it.
Using one hand, hook the hooked end of the jumper onto pin one (it should be marked) and hold it reasonably tight. Too tight, we'll straigten the wire and have to fix it again. Too loose and it falls off the pin.
Now carefully drag the other wire across each side of the other connectors pins, watching for flashes in the Screen Keyboard. Pay particular attention to the failed keys.
If you see any flashes at all, that line on the hooked connector is good. If it turns on the Caps Lock key, touch that pin again to turn it off. This way we avoid shorting out the Cap Lock LED.
Proceed to move the hook to pin number 2 and retest. Continue with each pin of the suspect connector. If they all pass but none of your bad keys appear to be pressed, test again then reverse your wire and test the other connector the same way.
If any of the lines produce no reaction at all when jumped; Note that line. It may not be a problem, but a ground line for the assembly. But then is could be our entire problem too.
When you do see one or more of our problem keys appear during this test, mark down the number of the hooked pin that it appeared on. Recheck that line to verify that all of the problem keys appear when jumpered with different lines on the other connector.
In this case, the problem keys all appeared when testing line 18 (of 19) on the large connector. This is good! It means a lot more work, but the problem is in the matrix itself and probably fixable.
If the bad keys did not appear while testing either connector than the Encoder chip is bad. We could carefully examine that all the traces on the Encoder Board are intact and repair any break we find. Then test again. We're not going to go into detail of that rare problem because it isn't the situation here.
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