All of sudden my "5" key doesn't work. But if I press any other number, i will get that number and the "5". Another symptoms is a running series of 5s in password boxes.

>because of what he described as the matrix design of the keyboard.<

Yes that is quite strange. Usually they go out in ordered multiples. Like "S - D - F" OR "W - S - X".

To explain the matrix design I recently replaced the top case in my 2011 13" MBP. I was interested in why the "Q - through - -P" keys all failed.

So I disassembled it.

This is the contactor array of a MacBook Pro 2011 13" . You're looking at it from back to front. Those round dots are where the silicone rubber "cones" cause the front array to make contact with the back array, telling the computer which key has been pushed. The width of these (I think deposited silver ) traces is about 0.5 mm.

Now you're only looking at the just the front array. You can see that the contact pads are connected in series. A break anywhere in the trace connecting them would cause the "downstream" keys to stop working.

So here you see a site where galvanic corrosion occurred.

So you can see from the amount of corrosion, it doesn't take much to cause a failure. In this case a drop of liquid less than 0.5 mm would, over time with galvanic action, cause a failure.

When I took this keyboard apart I was shocked to find how much crap was trapped under and inside the keyboard. Especially since I pride myself in never having any food/drink near my "precious!"

So in your case my theory would be that something got into the membrane between the front and rear contacts of the "5" key. I'm thinking it was resistive because it caused the key to stop working but was of a low enough resistance to create a false signal. Thus when you pressed any other number key the logic board would see two signals. The key you pushed and also a "5". Autofills would see a constant "5".

I dunno but it's just a theory but I like it.

coyoteblue56 wrote:

Thanks. It does seem like a keyboard problem. I had a tech look at it and he couldn't see anything wrong but was reluctant to just replace the keyboard right away.

Well, there's no need to take the keyboard apart looking for problems... just connect it to a different computer and see if the same problems occur there. That's the most definitive test there is! If the problem happens on any system the keyboard is connected to, it doesn't matter whether the tech can explain the cause of the fault or not, it's the keyboard. On the other hand, if this doesn't happen, it's something else besides the keyboard. That seems unlikely, though. I can't envision any kind of software issue that would cause the described behavior.

This sounds like a hardware problem with the keyboard.