On Sunday, January 10, 2016 at 6:09:21 AM UTC+5:30, Cursitor Doom wrote:
Finally got around to taking the thing apart. There was a tiny almost
invisible green-colored fibre no more than the thickness of a hair lodged
between the '2' ferrite core and its coresponding capacitive film backing
acetate pad. Had to examine it under a stereoscope to spot it it was that
tiny. Brushed it away and the pad's working fine again. That 1/000"
obstacle was the issue! Hopefully working again for another 25yrs now.
Thanks, all.

dude it was little helpfull for me. I removed stucked rubber of the buttons on the circuit witch the screw drivers nail - point and it worked. Thanks.