Someone else can correct me if I am wrong, I think the smaller pic, is due to the B+ being under 120DC. I know this can't be adjusted on FBO chassis, so that leads me to believe something previous to that, is causing the issue. Shotgunning it, I would look at the VR, R908 being in range(47k Ω 1/2 watt resistor), and ensure to reflow anything previous in circuit before the B+ test point. Bob's rebuild kit will not include the R908 resistor, I mention that, in case you need to replace it.
I know having a similar problem of filling the screen with a CBO chassis, you turn up the B+ a hair more than 120DC, and you can resolve the issue.