The picture rolls up and down the screen con- tinuously unless the vertical hold control is set at
its maximum position. Then the picture will only
lock with the bottom half at the top of the screen and the top at the bottom.
I have checked V22 and V23 by substitution and
have found them to be in order. -E. Ii. Houlsden
(Girton, Cambridge). Suspect an open circuit interference limited
control. This is in parallel with the frame hold
control h.t. feed.