Is the high-voltage OK (26-28KV) ?
Are the CRT heater filimments glowing ?
Is the G1 voltage OK (-20 to -60 V) ??
Is the G2 screen voltage OK (350 - 600V) ??
If above is OK, try connecting a 1K resistor
for one of the video color cathode pins on
the CRT socket to gound. The screen should
turn on with that color.
Hope ythis helps....
John