1966 Zenith 20X1C36 failed vertical output transformer

[Dave Drez]

Thanks for all of your input!

I spent most of today troubleshooting the vertical linearity issue. I did not find any "smoking gun" components that were bad, although I am ordering some caps and will replace as these are original. I do not have a tester that can test for leaky caps... (maybe I should). I'm not sure if ESR testers help with old TVs... Everything I test, the Blue ESR meter says it's OK.

The linearity control does effect the bias at the cathode, as it should. The only question is the grid. I see a proper waveform with the correct voltage at the grid. The Sams says there should be -5 volts DC at the grid and I don't have anything.

I reached an alright compromise today by using the relative interactivity of all the controls. I compressed the height via the "ineffective" vert linear control and expanded the vertical size to get near the correct height, then adjusted the vertical centering. Back and forth a few rounds and to my surprise, the linearity had changed for the better. A couple of the controls are at their maximum travel though. The image has a kind of "bubble" look to it but when I adjust the pincushion transformer, it doesn't have the change I expected. I'd call it "tilt" from my CRT projector days (maybe this is my trouble?). Adjusting the convergence helped with the improved appearance of the geometry as well.

So anyway, fooling around with those things improved the geometry to a point it's watchable but I am going to keep at it. Feel free to tell me it is as good as it gets!

Thanks,

Dave

[JohnCT]

Originally Posted by Dave Drez

I reached an alright compromise today by using the relative interactivity of all the controls.

LOL, they do indeed affect each other! Raising and lowering the height control constantly affects the lin, so any adjustments of height and lin need to be back and forth along with the centering. I always hated the vert adjustment dance and sometimes - just when you had it real close -you'd find that the vertical sync was iffy with the best geometry!

I'll never forget the first time I adjusted the vertical height on a SS TV back in the early 70s. I couldn't believe the height control adjusted only the vertical scan height, and that there was no linearity adjustment whatsoever.

John