Keyboard socket signal line leakage causes keyboard invalid

Host configuration of the keyboard self-test, the screen prompts keyboard error Pressto RESUME, press any key is invalid.

Connect the keyboard with other computers, self-test, input characters can be normal, indicating the failure of the motherboard on the keyboard control interface. Using a multimeter to measure the keyboard +5v, GND, Kbddata, KBDCLK These 4 signals, found that the KBDCLK signal is low level, and -0.65v. Check the keyboard cable intact, step by step forward, the result is the keyboard socket KBDCLK signal line and the motherboard -12v power line leakage, the reason is -12v printed line on the paint off, dust up the role of the conductor. Use brush to clean, and then use anhydrous alcohol to scrub it clean, the fault disappeared.