I have replaced the selenium rectifier with a BY100. I have also replaced the main smoothing
capacitor. The line timebase valves have been
replaced together with those in the field time – base, sync separator and turret. The picture still continues to jump all the time and cannot be stopped. The line hold control is rather critical and either side of a point the vision -on -sound noise is very loud. Cramping on the right side of the picture is evident and the verticals on the picture mostly to the left-hand side, have a double curve in them from top to bottom.-L. Whittall (Old- bury, near Birmingham).
Make sure that you have not given Your receiver excessive h.t. by fitting a BY100. Other causes of your symptoms are imbalance in the flywheel sync discriminator section, or a fault in the i.f. alignment