If the image is square but just tilted then the fix is usually easy. The yoke
is twisted on the neck of the CRT. Take the back off the case. Locate and
loosen the locking screw, normally only one. Rotate the yoke to correct the
tilt. Be very careful, many loose high voltages. I like putting a mirror in
front of the screen so I can see where I put my hands.
Good luck.
Paxton