I have a Sanyo CRT TV model CAP 6021 TX with twin speakers bought 10 years ago. Why I have to bang it hard?

before I could switch the set on? Another trouble is the TV could not stay "on" for long. It shuts itself down like going into sleep mode. To get it on again I have to hit it again; sometimes hard, sometimes just a light bang on the cabinet will do. Funny, though, sometimes it could go on for days! I know I seem to expect miracle from such an old set. I only need to use for a few more months; I have made up my mind on a full-HD Sony LCD, and will definitely take the plunge as soon as the price drops another two thousand MRs. Can anybody help how to prevent the TV from shutting itself down?