[old_tv_nut]

Note that the three amplifier cathodes are tied together on the right side of C135, to form the matrix from X and Z to R-Y, G-Y, and B-Y. Therefore, you have a mixed waveform at that point, which is not the opposite of the three different waveforms on the CRT grids. This is because each amplifier has a different waveform on its grid.

The waveform on the CRT grid will be approximately the opposite of the associated amplifier grid, but somewhat different due to the matrixing.

The G-Y amp has only DC on its grid, and therefore the green CRT grid will be the same polarity as the voltage on the common amplifier cathodes (but amplified).

So, what you will see on the right side of C135 is actually a G-Y signal.

Note that there is a large negative blanking pulse connected to the amplifier cathodes, so this negative pulse appears on the CRT grids also. This is easiest to see on the green CRT grid.