1950s or '60s vintage Zenith TVs, Need some info

[vortalexfan]

A little Update: I hooked my B & K 1076 up to the IF Input on the 23" Zenith and I was able to get a weak intermittent IF Signal on the TV and so I twerkulated the IF tubes in their sockets just to see if maybe there was a loose or intermittent connection in the tube sockets and sure enough I wiggled the 6EJ7 3rd IF tube and the IF signal would go in and out intermittently and so I removed the tube (it was the original Zenith badged Telefunken tube) and so I replaced it with a NOS GE 6EJ7 tube and sure enough the IF circuitry woke right up and was producing a nearly perfect picture (except for a little weird issue at the top of the screen, which is I think a vertical issue, but maybe you guys can tell what it is when you look at the pictue I took of the screen on the TV.)

This TV has a really nice bright raster yet which tells me that for sure this was definitely a low hours TV (possibly just used as furniture, or only used on special occasions.)

one thing can't figure out is that the backlight circuitry on this TV for the tuner is kind of intermittent for some reason.

When you first turn on the TV the tuner backlight is dead (isn't glowing) and then after the TV warms up a bit then the backlight comes on and when you "scan" through the channels the pilot light for the UHF tuner won't come on right away when you hit the "UHF" position, I have to smack the side of the TV a little bit and then it comes on.

Any ideas as to what's going on here?

See picture below for a view of what the screen currently looks like on the 23" Zenith.

P.S. I never touched the IF cans in this TV, the picture that this TV is producing right now (as seen in the picture below) is how the IF cans were set when I got the TV.