I am trying to adjust horizontal linearity. There is a faint vertical bar a little less than halfway across the screen, where the horizontal scanning is slightly compressed.
In the book “Basic Television” by Grob, he shows a picture of a much more pronounced vertical bar in the same region of the screen, and says it is excessive horizontal drive.
I know this is the region where the damper diode stops scanning the left hand side of the screen and the horizontal output tube starts scanning, so I replaced the damper tube since it looked like the original Magnavox branded tube and looked very baked and worn. However, replacing the damper tube didn’t help. The previous owner, who last used the TV in the 1970s, had replaced the horizontal output tube 6JE6A, with the much cathode higher current rated GE branded 6MJ6, and it still looks new. So I don’t think it needs to be replaced.
The Sams only describes adjusting the horizontal efficiency coil. It never mentions adjusting the “horiz waveform” coil. Which coil should I adjust to fix this horizontal compression issue? There is no horizontal drive control in this TV.
I think the right thing to adjust is the horizontal efficiency coil, but I wanted to confirm, and I also wanted to know what the “horiz waveform” coil does. The horizontal efficiency coil used to be called the horizontal linearity coil. It adjusts the current of the damper and the horizontal output tubes in the region where they both are partially conducting, and I guess you could call this distortion a type of “foldover”, though it is a very minor form of foldover that is barely visible.
The “Horizontal Sweep Servicing Handbook” by Darr describes two possible adjustments: horizontal linearity coil and horizontal drive. If horizontal drive is “overdriven”, then grid clipping causes excessive grid-leak bias, which means the horizontal output tube doesn’t turn on soon enough. The “drive line” is very pronounced and white. This doesn’t seem to match the subtle bar that my TV is manifesting.
