DECCA CTV19

The trouble with this set is lack of field scan at the top and
bottom of the screen. Neither valve replacements nor
adjustments to the presets in the field timebase improves
matters.
The most likely cause of the trouble is over on the line
output stage chassis, where the RC network R405 (1M52,
1W) and C403 (1µF) filters the supply to the field charging
circuit. If necessary check R308 (470k52), which is in series
with the height control. If the linearity is impaired, suspect the
electrolytics associated with the field output stage — C308
(32µF), C311 (400µF) and C327 (400 uF) — also the field
output pentode’s cathode bias resistor R314 (47052, 5W).