(newbie question) Dead Keyboards

I'm trying to find out watch out for when opening keyboard. I'm asking because I think I've killed two of mine.

They're both "budget" types - membranes & rubber springs on the keys. But I've opened two up and now one doesn't funcation at all (except for the scroll/num lock light) and the other where some of the keys don't work (and none of the lights will turn on).

I'm asking because I *really* need to be able to open up and mod a small keyboard for a case I'm working on that I want to fit a keyboard to.