Is it possible? I've been wondering this for awhile. Sometimes I find a TV where the CRT is dim. Upping the VG2 voltage brightens it, but at the expense of contrast.

Usually the CRT still has good color, and shows no color bleeding, but I have to max out the contrast to get a decent black level while still maintaining decent brightness.

In my experience, this means that either the HV supply is low or the fly is getting kind of weak. Try bumping up the capacitance in the horizontal section as well as the main filter caps if you have a blooming issue. But, if the CRT is on its way out, well then of course you're out of options.

The old tv repair FAQ has a method where you increase 2nd anode voltage by wrapping some wire around the flyback but that puts more of a strain on the transformer.

...

So, I'm guessing the best I can do is up the brightness to the point where the black levels are still decent, and just hope the tube has a good enough picture?