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Check the CRT cathode and first grid voltages (all gun voltages should be checked but grid and cathode are the most important) in comparison to those listed in the schematic (vary brightness and contrast and see if what is listed in schematic falls inside the range the controls give)...if those voltages can't match the schematic then you need to figure out why.
Get a HV probe for your DMM or an HV meter. You need to know the value of the HV to see if it is low...
Have you optimized the ion trap for brightest picture?
You have what is considered to be a weak raster. Raster is a lit screen with horizontal and vertical deflection present. If focus is poor you won't be able to see individual scanines even if the set has an otherwise perfect picture. Poor focus on a 10BP4 CRT is either an incorrectly set focus control, bad to us coil positioning, or poor HV or gun bias issues.
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