CRT still holding up

[zenith2134]

The contrast level (video gain level) is more likely to affect the 'bleeding' issue in a weak CRT. Yes chroma level and brightness also affect it to a lesser degree. If you were able to somehow replace the video output transistor for the weakened gun with a higher-gain/or transistor with higher dissipation characteristics, the problem might be less prominent. In a crt which is marginal, the video output devices on the neckboard have to work harder to drive their respective cathode. The result is a form of clipping/saturation distortion.