The line and field sync on this set are poor – both hold
controls have to be continually adjusted. It’s also necessary
to readjust whenever the channel is changed.
A PCF80 is used as the sync separator. You will
probably find that its screen grid feed resistor R63 (330kS2),
connected to pin 3, has increased in value. Also check its
anode load resistor R66 (220k52) which is connected to pin
6. (ITT VC52 chassis.)