Motorola VT-71 TS-4D Horizontal Jittering Image

[ChrisW6ATV]

Jon-

That is absolutely, exactly the same problem I have with my VT-71 as well, which is also a TS-4D chassis. I started a discussion (with a similar title) on the Antique Radio Forums TV section a month or so ago, and got a number of helpful ideas and suggestions, but nothing has fixed mine yet. Since I have been busy with several other non-antique-TV projects and events, I have not got back into my set for a while, but my next step was to put an oscilloscope into the horizontal, video, and AGC circuits to see what I could find.

Starting the the TS-4E chassis, Motorola added a horizontal AFC circuit (and that version is what is in the Sams Photofact manual, more or less), so I suspect that this problem is common in the TS-4D and earlier chassis to one extent or another.

The one trick/clue I have found is that when I played with the horizontal hold control, I got the set into some mode where the picture was split horizontally but seemed to be in sync; the "horizontal phase" was way off, I think it can be called, and the vertical sync bar was visible in the picture. I forgot if it was in or near the center, or off to one side. The big kick, though, is that the (out of phase) horizontal sync seemed very steady! So, if anyone has ideas of what that means, I would like to know, and maybe it will help both of our sets. My intent was to connect my scope if/when I can get the set into that out-of-phase mode again, as well.