good point. I seem to recall that there is an adj that is an add'l blue adj for convergence tied into that adj. I recall cause I was reading a service manual and it called out a final step for which I could not see the adj (was not on the dynamic board and I was only thinking of the reg 4 adj for manual (reg 3 and blue lateral). then they mentioned on some note the final blue adj that was a nut you loosed on the bottom of the yoke to tilt it some more, I guess to be done after purity.
When I get brave I may mess with that
All wrapped up around the axles on my philco roundie the the moment.
side note on the zenith, the vert out tube seems to be either just a loose socket mount or a soft mount socket with rubber that has deteriorated some. check you vert out tube and see if the socket does not rock around somewhat next time you are into it. I can see what looks like loose fitting rivuts on the socket flange.