[old_tv_nut]

You can do minor gray scale tracking on a picture, but it's best if it's a still test pattern with a full range from black to white, like color bars. And it's really best to have the service switch. The problem is that the brightness control and G2 controls have similar effects on the picture, so it's hard to tell if they have been set in opposite compensating directions. The service switch puts a fixed bias on the tube so that when you adjust the G2's you are setting them for design center normal cathode and G1 voltages, and the video output tube has the fullest possible range available.

So, yes, you can tweak the G2 controls, but when you get the service switch fixed, you may find that all three are off by some amount.

If you want to play with it now (and maybe have to readjust later), the principle is to turn the color all the way down, set brightness to mid range, and make the blacks just black and colorless, and the dark grays also the same gray as the highlights, with the G2 controls. Then if all the shades of gray from black to white are off color (but are the same color, that is they are tracking), adjust the green and blue drive. You may have to go back and forth from drives to G2s a time or two.

It's the setting of brightness arbitrarily to midrange that may cause a discrepancy with the service switch procedure, but what the hey, if you want to try it, go ahead.