laptops keyboard not working well ...

[sa.saru98]

hi

i have acer travelmate 5540

i bought it from a friend and it happens to have some keys not working like the whole top keys ; esc, f1, f2, f3, f4 and so on and the left shift, number eight, and four, six

when it seems its in very good condition, i tried and cleaned it from dust, getting it out of the laptop and re-installing it ..

i tried as well a trick that seems to be working for some people but not me

which is turning of the laptop getting out the cable, battery and holding the power button for 60 seconds.. 

can anyone suggest a solution ? and thanks!