Contrast

[VA561]

I have a 1950 philco tv , model # 50T-1404. The tv has been recapped and all weak or shorted tubes replaced.The problem is this: the brightness is pretty good on the tv but with the contrast turned all the way up I still get a somewhat washed out picture. I try to get a balance between the brightness and contrast controls but there just isnt enough contrast. what causes the lack of contrast? Is it the picture tube or some other area. Any input will be appreciated.