Please Help, Sony E200 17" - Poor Contrast

the monitor was used fof about 5 years (not by me). and it has a problem - the picture is too mild, even when I set contrast to 100% it's not enough. I know 5 years is a long term and at first I thought that the gun began dying but I think it's not the case, cause when I enter a menu , white background of the menu is perfectly white and looks great, but the picture behind it is way too mild.
I used 2 video cards (nvidia) and the picture is more or less the same. Maybe the signal is too weak?Or the cable is damaged?

If there is a way to increase contrast internally can yyou explain me how should I adjust it?

Thanx