Want to make a Telematic #57 convergence aadapter
 

We're going to be snowed in for the day, and I'd like to work on my chassis for my zenith. I'm going to bring it in and use my telematic test jig, does anyone know how to make a number 57 convergence adapter?

I have modified and built yoke adapters for the color-TV jigs, but not any convergence adapters. Maybe your "plan B" would be to compare schematics for other Zenith sets from the same age with your set, if you have other convergence adapters. Then, you might be able to modify or make one. I know that the early color TV sets all used the same adapter, and inside it is just one resistor if I remember what I read about it.

If you have any convergence adapter that fits any set you recognize/have a schematic for then you can try to reverse engineer what's going on. I had to do that for deflection on my jig to connect my 21CT55.
Some 60s roundys have a lytic and power resistor that part of the vertical power supply flows through and some don't.... Sets that have it will have insufficient vertical without it or with a different style convergence board... There's probably the same thing in some rectangular TVs too.

Besides making sure the power path for the vertical is OK I typically don't bother with convergence on my test jig. Any convergence circuit issues need to be solved by troubleshooting with the convergence board that's part of the console the chassis belongs with. Minor deflection issues also have to be solved in the console that the TV belongs with as test jig universal yokes may have ringing and linearity issues that the actual yoke in the console won't have. You can definitely troubleshoot major deflection issues on the jig.

Also a final thought: Why would you ever pull the chassis out of a Zenith to troubleshoot it on a jig? Zeniths have the service saver hatch on the bottom of the cabinet that gives you full access to the under chassis. If you have the back off and the bottom hatch off and the cabinet on it's side there shouldn't be any part that you can't access. On TV only consoles and smaller I pull the back and bottom and turn the set on it's side usually on a sturdy table, on combos I usually turn the whole combo on its side and work on it where it sits.
The only reason to jig a Zenith is if it's a customer set and you don't want to drag the cabinet to your shop or set up shop around it at the customers place.
About the only time I'll pull a Zenith chassis I own is if the CRT has to come out for a cataract or replacement.