RCA 6T75 Horizontal Linearity

[dobulee]

MadMan had posted some comments in his admiral restoration about working out some horizontal linearity issues with the horizontal driver trimmer, rather than with the horizontal linearity control.

My KCS47T Chassis has always had 'crowding' at the right hand side of the picture (indeed, the 'half' more or less controlled by the Horiz output Tube). Some HO Tubes were worse than others when I tried tube swapping years ago. Given MadMan's comments, I decided to give it another look and play with the horizontal drive trimmer, which this chassis also has.

IT's worth noting that both SAMs and Breitman DO have some comments about adjusting the drive trimmer as far as possible without crowding the picture, but somehow I had always missed it - wasn't on the radar.

I couldn't find my test pattern rig, so I used some repeating patterns in video game graphics as a benchmark. Tell you what - the difference is substantial!

Ive attached before and 'best adjusted' pictures below. Look at the right hand side of the screen.

The linearity isn't perfect, both edges are still crowded compared to center, but it's much less offensive. At this point the vertical linearity is worse, but no amount of fiddling with vert linearity, height, and recentering the picture at the yoke has ever made much difference there.

In a later post, I do need some help -- my horizontal linearity slug is stuck - I'll post some pics, and see if anybody has ideas.

FWIW, this set does have DC Restore at the synch separator tube, so I"ve posted an image with mostly black background for reference. It looks better in pictures than in real life. There is still some image smearing, but I consider that to be the nature of the beast with this set.

Thanks for the help. It was fun to dig into this chassis again.