Author Topic: Laptop Keyboard Repair  (Read 192 times)

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Offline OpenCircuit

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Laptop Keyboard Repair
« on: February 19, 2020, 11:59:46 pm »
The W, S X keys and the LED back lights are not illuminating on this keyboard. Probing the obvious voltage supply for the back lights (A4NA14) it appears A4NA 14 is not passing 5V through to the top-right pin of A4NA 14 when the laptop is powered on. I dont know if the A4NA 14 is faulty or if it is not receiving power on command from another source on the mainboard. When the laptop is powered on current is 280ma across the 5v pin and the top-right pin of A4NA 14 and the back lights illuminate when checked with DMM. Problem likely with A4NA 14 or something else?  12V goes to 0v when the laptop is powered on. Can't seem to find specs on A4NA 14  :-//



EDIT: Found a KB9028Q C which appears to be a keyboard controller.
« Last Edit: February 20, 2020, 02:15:46 am by OpenCircuit »
 

Offline OpenCircuit

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Re: Laptop Keyboard Repair
« Reply #1 on: February 20, 2020, 08:17:22 pm »
It appears Q8 controls the gate on Q7 and Q7 being controlled by the "KB_LED_EN" signal? I can increase voltage to back lights positive by simply touching the neg and pos terminals on the probes and voltage will rise to to almost 2 volts to the backligths.

What to replace first?


« Last Edit: February 20, 2020, 08:42:19 pm by OpenCircuit »
 


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