[old_tv_nut]

The video is showing the efficiency adjustment as an isolated procedure and assumes the other adjustments in the SAMS are nominal.

SAMS adjustments:
The first two, for "floating" H sync, are to set the H oscillator to free run at nominal frequency so the horizontal AFC and horizontal hold controls are centered and don't have to pull it one way or the other to an extreme degree. I'm not sure, but maybe being way off center could affect the horizontal drive waveform, which in turn would affect the output efficiency.

[video procedure goes here]

The measurement across R136 is actually across R146 in the SAMS schematic on ETF. This is the HV regulator cathode resistor. Caution, it is floating at about 400v. This adjustment is to check if the HV regulator range is more or less centered. If not, you are instructed to detune the efficiency coil to get more HV supply, but simultaneously not go beyond the horizontal output cathode current limit. Ideally you should be using two meters at once (if not, you need to go back and recheck the HO cathode current).

Finally, you are similarly instructed to detune the efficiency coil slightly if you see horizontal fold-over in the picture (and should recheck the HO cathode current just to be safe).