Drive line Question

[Penthode]

Going back to the drive line business, I think it is important to understand the drive line is a result of a horizontal scan pause during the active trace eg left to right. The HO Tube is generally dependent on grid leak bias from the drive of the horizontal oscillator. If the amplitude of the oscillator signal is excessive, the HO Tube will have excessive bias due to control grid rectification hence will not begin conduction until too late. Hence the line.

I earlier suggested the 6CD6 with higher than normal transconductance may resulted in the drive line because the control grid negative cut off potential would be less. I would be curious if Bob could subject the offending HO Tube to a transconductance checker to determine if this is true.

It therefore appears that the appearance of the drive line is due to either or a combination of these two factors: excessive horizontal output amplitude output and/or HO Tube cut off characteristics.