tv picture distortion

[tesseract131]

I have a 10 yr old Magnavox (Philips) TR2710 C102 that took about an
hour to go from a normal picture to a totally rolling screen. It
started to shift the picture from the left to right from about halfway
up the screen moving slow to the top, the darker the picture the worse
the distortion. On a totally or almost totally dark screen is when
its at its worse. I adjusted the horz cent all the way clockwise
which took most the problem away, bumping the brightness up helps but
washes out the picture. What needs replaced? Thank you.
and please go easy on me, im new to this fixing old tv thing, lol