With the color all the way down, the picture is pretty much like any other color TV with the color down. I noticed, turning it off, a very brief tricolor flash in the upper center of the screen and if I turn it back on immediately the picture is deep blue for an instant before it goes to black & white.
I used a transistor checker on all three original gun transistors and they all were pretty much in the same ballpark. I changed the red gun transistor anyway and it made no difference. The only difference I can find among the three gun circuits is that R73, in the red circuit, is 230-300 K where its counterparts in the other two circuits are around 100 K. Would this kill the red color level, by any chance? I'd put new 150K resistors in all three slots except I discovered when I got home that I'd bought 150 ohm resistors instead.
jpdylon, from your earlier comment I think I'd better change out the 150K resistors before I try to do a grayscale setup.
On another matter entirely, the gray (I think; mine's gone kind of olive drab) plastic clamp that goes around the base of the picture tube has broken right across at the base of one of the tabs that holds the pinch screw. Is this glueable with epoxy or do I need a new clamp?