screen rolls like an old tv when the vertical hold was off

First of all the screen went grey and had lines through it - now it just scrolls down continually. When i turn it off and then on again, it's ok for a short while and the image just rolls down the screen like an old analogue tv when the vertical hold needs adjusting.?? i cannot find any posts re this except this on youtube

https://www.youtube.com/watch?v=AW0dunNt...

o