I don't think a damaged membrane can be repaired. The warranty has also been void as you opened the KB. Still, ask some local shops for repair, if possible or get a new combo.
just get a new kb ..
there are tonnes available at around Rs 400-500
Personaly, I'm using logitech mk200. The only problem with them is (like all membrane keyboards) is that the keys become loose after an year or so.
Personaly, I'm using logitech mk200. The only problem with them is (like all membrane keyboards) is that the keys become loose after an year or so.