[TinCanAlley]

Originally Posted by andy

You always want to do gray scale with the color off, or with a pure B/W signal. The G2 controls adjust the brightness of each color, and the taps adjust the contrast of each color. You adjust the G2 for neutral balance of dark gray (almost black), and the (drive) taps are used to balance high brightness areas of the picture.

My one complaint about Zenith TVs from the 70's is that to save money they replaced the drive controls with those three position jumpers. It makes it impossible to get perfect gray scale unless you get really lucky with the CRT.

Having said all that, the first thing I would do is measure the G2 voltage to all 3 guns to make sure that the G2 controls are working properly. Normally, you should be able to adjust the service line from black to fairly bright on all 3 guns. If the G2 supply is low, or there's a problem with one of the controls, you won't be able to adjust it properly.

Where would I measure the G2 voltages? From the CRT socket? If so, do I just pull the socket off while it's operating, put the black probe to chassis ground and stick the red one in each socket and note the voltage? Do I move the G2 control back and forth while measuring?

I have the service manual, but it's the electronic version and it's not clear enough to note all the voltages on the socket. These are the ones I can read okay, but the 13 and 4 are blurry:

Pin:

2- 143V
11 - 142V
6 - 142V
7 - 36.4V
12 - 36.4V
3 - 36.4V
5 - 540V
13 - 640V
4 - 540V
9 - 3.5kV

If those voltages are correct, I can do all but the last 4 as my meter only goes as high as 500V. Oh, and are those AC or DC volts?