1) on the CRT board there are 3 identical 2W resistors. They feed the
R,G & B outputs. Where they join is apx 200VDC. Follow that line & you
will come to a cap typ 4.7 mfd 350 volts. change it.
2) check resistors off the G-2 control. High ohm values & they like to
open.
3) blue line at top is probably the AKB ( automatic kine bias) firing.
With AKB each gun is fired & measured during retrace & automaticly
adjusts the grey scale. Normaly on a Sony with AKB & a weak CRT
the video will blink on & off but less as the set warms.
4) keep in mind the cathode voltages will all be a little different.
The lower the voltage the higher the brightness of that color.
73 Zeno
LFOD !