Seeking person experienced with Motherboard repair/Ribbon Cabling

[Sauro]

Hello,
When using my laptop (Dell Studio xps 1640) about a week ago the entire keyboard ceased to function. I purchased a new one, installed it, and all the keys work except for n m h j y u 6 7 (A diagonal row near the middle). I assumed the seller sent me a faulty keyboard and returned it while purchasing a new one from a different seller. New keyboard arrives and a new set of keys on it do not work (left right arrows, b n space bar / ).

Now I'm guessing two possibilities at this moment. I have been woefully unlucky and received two bad keyboards, or one of the motherboard contacts is damaged. My thought is that the two keyboards may use different strands of the ribbon for certain key combinations.

My question is whether or not anyone has seen this problem, or if they have any experiences repairing these ribbon connecting style keyboards, or just has a wider amount of knowledge to assist me with.


Thank you very much.


What I have tried so far: Send at least an hour removing the board from the laptop and cleaning all the associated contacts.

Cut the original ribbon cable so that different strands touch different contacts (None worked when I did this, so I assume that the entire thing needs to be in there in order to function).

 

[Sauro]

Since this post I have been able to check continuity from points on the motherboard where the keyboard ribbon cable sits to the leads that going into the board itself. The next thing I would like to check is either continuity between the ribbon cable strands and these leads, or check the leads themselves for changes in voltage when keys are depressed (I am assuming this would be a change in voltage, but I'm not extremely proficient with a multimeter, or positive it would be a change in voltage, so help here would be wonderful.)