If you're 468 has socketed transistors, your best bet is going to be to pull the vertical amp board and check all the semiconductors on it. It sounds like there is a major offset in the voltages between the vertical deflection plates.
It would help if you put some signals into the inputs and gathered some more info. Dig into the Volume 1 manual and run the vertical section performance check, subbing equipment as you need to. If frequency isn't stated, such as for the amplitude calibrator equipment checks, the frequency is 1Khz.