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Locating keyboard controller on asus ultrabook motherboard

PostPosted: Thu Apr 14, 2016 4:49 pm
by solderking
I have an ASUS UX301LA-XH72T ultrabook. I find myself with a very specific problem.

The seventh pin on the keyboard connector has been severed somewhere along the way to the keyboard controller along the motherboard, or the keyboard controller itself is damaged.

We have attempted to deduce where the keyboard controller is and where all those keyboard connector pins lead to however we cannot find it. Our strategy for repair is to short the pin directly to the keyboard controller assuming it is even possible.

I have attached 2 pictures which include most of the motherboard and a close up of the keyboard connector. Do not mind the scuffs and scratches, we have verified that those circuits are not damaged.

Any assistance in finding where the keyboard connector pins end up going to on the motherboard would be appreciated.


Re: Locating keyboard controller on asus ultrabook motherboa

PostPosted: Fri Apr 15, 2016 5:48 am
by Karlsweldt
A cold-solder joint is common, and may be easy to fix. A pencil soldering iron of about 35 watts, some rosin solder, and a stainless steel dental pick are the tools needed. (Solder won't adhere to stainless steel as easily as most other metals.) Hold down the contact tab with the dental pick, a small dab of solder after 2 seconds on the tab with the iron, and should be good. Too long with the heat could damage circuitry or nearby chips.
There could be up to five layers of circuit traces in a motherboard! Only the manufacturer has the diagrams, and is reluctant to release them for viewing. Copyrighted property.

Re: Locating keyboard controller on asus ultrabook motherboa

PostPosted: Sun Apr 17, 2016 10:10 pm
by Twisty
By working out what intel chipset is used might help you identify what chip you are looking for for the serial/keyboard controller.
You can also try attaching a 9V battery to pin 7 and ground (maybe have a resistor between -ve and motherboard groundplane just to be safe) and then trying to help you probe out where it leads using a voltmeter (one lead grounded the other probing) but as pointed out the PCB is multilayer so difficult to follow traces.
It is worth checking it isn't a dry joint between IC and pad (at either end) before resorting to connecting the pins directly (tip: old bit of cat5/5E tends to yield nice bits of solid core patch wires with multi coloured insulation :)