Sony KV-M1411U Video display issues

[Dagare]

Thanks for the response Zeno.
So if I've understood everything correctly, there are at least two issues.
Video input is dead, but osd + top rgb lines are there, so the issue has to be between the jungle ic and input, as its a direct line to the neckboard from jungle and osd shares rgb input from what I can see on the schematic.
Then either the tube is worn or there is an issue on the neckboard.
With g2 set correctly but reducing vertical size, the blue line shows fine, but red and green only show after boosting g2.
If I disconnect the vid input cable from the neckboard, the screen is still blue when boosting g2.
Do I need to input a white screen to check the tubes health?