If you can obtain a full intensity raster by varying the brightness or screen
control, then your problem is most likely in the video amplifiers or power
for the video amplifiers.
If, however, the screen control varies the brightness but will not get
a bright raster, you probably have problems either with the HV power supply
or the filament supply for the CRT - is there the normal bright orange
glow at the base of the CRT? If it is dim or very reddish, there may
be a marginal connection or bad component in the filament circuitry.
