[old_tv_nut]

According to the schematic, there should be about 5 volts difference across R154 (260 V on supply side, dropped to 255 V at the plate of chroma bandpass). You could measure the supply and the plate voltage and see if they are 5 volts different. When the color killer operates, the bandpass amp is cut off and there will be no drop.

So, go back to grounding point E. This should defeat the color killer and let the bandpass amp conduct. Turn the color control all the way up and see if you see any color.

As far as using the scope, set the scope sweep rate to horizontal sweep rate (about 10 microseconds per division). For starters, set the vertical sensitivity to 10 volts per division (or 1 volt if you have a 10X probe) and check for presence of all the waveforms shown in the SAMS schematic for the chroma sync phase detector and color killer, plus the chroma bandpass. Set the vertical to higher gain to view the smaller waveforms that are marked about 10 or 12 volts peak to peak.

Do you have a color bar test pattern to use, or are you using some program video? The chroma waveform on pin 3 of coil A14 will generally not be as big and obvious with program material as with a test pattern, but you should be able to see it come and go when the color killer operates.

Also look for the chroma at point G, pin 1 of V23 X demodulator (or pin 1 of V21, Z demodulator).