Question How to know which traces are broken and how to lay one over another laptop keyboard pcb?

Oct 30, 2021
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Hi, i opened a few questions here, but all them stayed answerless. So, i need your help again. A few months ago, 8 keys of my laptop keyboard started not working. So, i opened my laptop and bring the keyboard out. I disassembled all keys and separated circuit board to 2 parts( this parts was one lay over another). So i tested the traces with multimeter and got values between 2 and 7 ( mostly was 5). And i decided trying to use it one more time before starting to repair. But when i turned keyboard back and started laptop, none of the keys was working. After this i tried to repair it, but none of the keys working when i try to use it normally. Keys working when i touch one lay's traces with another one and writes so many character, but if i try to turn it back and use normally, no keys will work. I am so depressed about it cuz, the price of this keyboard in my country is equal to my salary. This makes me disappointed. Please, anyone help me about this issue, this situation is about to drive me mad. I am adding a photo of it:


PLEASE HELP😓
 

Eximo

Titan
Ambassador
External keyboard would seem to be the best quick fix here.

But a replacement is probably your only option at this point if you want the full functionality of the laptop.

I can't really say what is broken or what you may have damaged running a multimeter through a keyboard. They work by injecting a little voltage with a very large resistor value in parallel. Shouldn't cause problems most of the time, but most keyboards are capacitive devices, but are likely to be at 5V internally. Most multimeters operate at 9V, so it is possible something has been damaged in the keyboards logic circuits.
 
Reactions: Mandark
You can’t repair you laptop kb pcb. You don’t have the schematics the tools and probably not the skill either so why do you ask questions that can’t be answered? You’ve been answered in two of your threads telling you to buy an $18 replacement keyboard and just replace it and that’s how you fix it. You’re looking for a magic bullet and you’re not even gonna be able to fix it even if somebody told you how
 
Reactions: rgd1101
Oct 30, 2021
10
0
10
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You can’t repair you laptop kb pcb. You don’t have the schematics the tools and probably not the skill either so why do you ask questions that can’t be answered? You’ve been answered in two of your threads telling you to buy an $18 replacement keyboard and just replace it and that’s how you fix it. You’re looking for a magic bullet and you’re not even gonna be able to fix it even if somebody told you how
So, probably i was waiting for a miracle. The price of this keyboard is 50 usd in my country and this is equal to my salary for being a teacher for one month. I am sorry if i bothered you. I just hoped someone had same situation will come and say me the secret of this repairing. I am sorry about creating so much threads and bothering everyone. I won't do this anymore. Take care
 
As far as can tell, typical laptop keyboards are ordinary resistive types. There is one sheet with the column contacts and a second sheet with the row contacts. The keyboard controller on the motherboard sends pulses down each row and watches for pulses appearing in each column.

https://www.instructables.com/How-to-Make-a-USB-Laptop-Keyboard-Controller/#:~:text=Laptop keyboards use a flexible printed circuit (FPC),and a plastic backing on the other side.

A DMM should do no harm. It outputs a maximum current of 1mA on the diode range with an open circuit voltage of 3V. The resistance ranges are much lower.
 
Oct 30, 2021
10
0
10
0
As far as can tell, typical laptop keyboards are ordinary resistive types. There is one sheet with the column contacts and a second sheet with the row contacts. The keyboard controller on the motherboard sends pulses down each row and watches for pulses appearing in each column.

https://www.instructables.com/How-to-Make-a-USB-Laptop-Keyboard-Controller/#:~:text=Laptop keyboards use a flexible printed circuit (FPC),and a plastic backing on the other side.

A DMM should do no harm. It outputs a maximum current of 1mA on the diode range with an open circuit voltage of 3V. The resistance ranges are much lower.
Thanks
 

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