Quote:
Originally Posted by Penthode
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.
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Another of my old books (
Horizontal Sweep Servicing Handbook) seems to agree with you:
"If we overdrive the output tube, we will cause distortion of the drive waveform, by grid-clipping, etc., and upset the normal timing of the plate current pulses. If we make the output tube cut off at the wrong time, we upset the resonance relations in the secondary and distort the sweep waveform of the yoke. The invariable symptom of this condition is a foldover in the center of the screen, in the transition area between damper and output tube conduction. This appears as a vertical white line in the raster, which is called a drive line. Of course, it should be called an
overdrive line, but you know how we are."
The book goes on to say that you can use the drive adjuster for diagnosis. If you
can't make a drive line appear, the horizontal oscillator output signal may be weak and should be checked out.
Phil Nelson