1990 Zenith horizontal width is too wide

Called overscan. And probably as it left the factory.;-( If no pot there could be a jumper or even an inductor. But be prepared for the geometry to go out even if you can set the width correctly.

There's almost a dozen pots on the board, none are marked. Can't find a schematic, how would one determine what to do without one? Thanks

You can experiment, but that would likely be very frustrating. Hope that someone else posts with some hints.

with the age of that set is is most definatly drifting caps look around the fly area for puffy caps that set has seen its days cheaper to by new

Don't even think of touching the pots! Modern TV sets don't just go out of adjustment, there's obviously a fault and if you start messing with the pots, no tech will be willing to touch the thing.

Reminds me of that old story about a valve radio brought in for repair - the customer says it worked fine until he hoovered out the dust and tightened up all the loose screws.

Nothing seemed puffy. It seemed to make no noticeable difference when I swapped out 2 mylar caps, 1 between the H drive transistor's C & B, 1 between it's B & E. The E is connected to the heat sink & what looked generally like ground, C to the flyback x-fmr through a ferrite bead, the B to a small x-fmr, I'm guessing for drive step-up. I don't have a schematic, anyone got one? Am I looking at the right caps?