I have an older laptop that was stored for some time. After taking it out of storage, the built-in keyboard began generating unwanted key presses, so I disconnected its ribbon cable from the motherboard and switched to an external keyboard. That worked for a couple of months, but the phantom input has now returned even though the internal keyboard is still disconnected. I have also unplugged the mouse, touchpad, keyboard-backlight cable, and all other peripherals. The problem occurs in both Windows and Ubuntu, so it does not appear to be an operating-system issue. How can I determine what is generating the key presses or disable it?
1 Answer
If the keyboard ribbon is fully disconnected and electrically isolated, the fault is probably no longer in the keyboard itself. A short, contamination, or corrosion around the keyboard connector or the laptop’s embedded-controller circuitry could be making the motherboard interpret signals as key presses. Inspect the connector and surrounding board closely for debris, liquid damage, or corrosion, and clean it carefully with appropriate electronics contact cleaner or isopropyl alcohol. If the behavior remains, the motherboard or embedded controller may be defective; software changes are unlikely to fix it because it happens in multiple operating systems.
The ribbon cable was isolated so it could not touch the motherboard, and the phantom input continued. I also disconnected the other removable input components, so the motherboard or its controller now seems like the most likely source.