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Thanks for posting the data sheet. That's one of the reasons why I posted this -- to find out to what extent operating with positive peak voltages on the red grid may cause some damage. I see on the data sheet that the max rating for grid voltage is +2 volts. Is there an additional reference on there specifically about grid current? I may have missed it.
One thing I noticed in the circuitry is that while the green and blue cathodes are fed by a fairly stiff voltage divider, the red cathode has an extra 2.7K cathode resistor. This reduces the gain of the red and reduces the positive grid voltage with respect to cathode. Shorting this resistor results in a pretty nonlinear response, where the red beam gets too bright on positive peaks and gets completely out of balance with the other colors. I tried reducing the value of that resistor and came away with the impression that it's best left alone. Intriguing, however, to think about how the red signal could be further boosted in some useful manner that gets rid of the nonlinearity. Maybe some kind of active feedback on the beam current? With a little help from a modern op amp that would be possible to do.
If any of you knows anything further about the risks of boosting the red in this way, let me know.
As miniman82 points out, I don't have so much to lose here, but I also don't want to completely kill the red very quickly by trying something completely crazy.
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