[Charlie]

I don't think you can use a brightener for just one gun. The heaters are all connected in parallel.

Have you already tried increasing the heater voltage on the tube? What were the results? How much do you have to increase the voltage before your red gun shows good on the meter?

If increasing the heater voltage brings the red gun up pretty quickly, then you have a good chance at correcting your problem just by letting it sit there for a while with the increased voltage.

Do you have a "clean" or "balance" feature on your crt tester? I would try that first. The rejuv function should always be your last choice since you can possibly do more harm than good with it.