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

[vortalexfan]

Originally Posted by jr_tech

With ch 3 at the 6:00 position, I suspect that ch 9 was at the 12:00 position, so the tv was actually tuned to ch 9. Ch 9 (186-192 mHz) falls in the range of the third harmonic of ch 3 (60-66 mHz), so is likely that the NES has a much stronger third harmonic output than your other devices, (poorer quality modulater).

jr

OK, so that exlains why I was able to get the NES to come in so well at the wrong channel (CH. 9 rather than CH. 3.)

It looks like what I need to do is set my converter box and RF Modulator to channel 3 hook them up to the TV antenna input and then fiddle with the local oscillator adjustments for channel 3 until it shows a proper image on the screen and then adjust the fine tuning knob (UHF Tuner Knob) and go from there.

I think other than the channel selector confusion I think we can call the Bugeye TV as good as fixed!

[vortalexfan]

Now onto trying to figure out the Big Zenith!

[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.

[Kevin Kuehn]

Primarily a vertical linearity issue. Could be linearity and/or height control or a cap. I don't have any service info so I'm not of much help.

[vortalexfan]

Originally Posted by Kevin Kuehn

Primarily a vertical linearity issue. Could be linearity and/or height control or a cap. I don't have any service info so I'm not of much help.

well that's what I was thinking as well, and I was trying to adjust the height adjustment (called Vertical Size on this TV) but that control is inset within the Peak Picture control and I can't seem to adjust it because none of my screwdrivers I have are long enough to go inside that Peak Picture contol knob to adjust the Vertical Size Adjustment.

[damen]

If your tuner has this switch on the back, it's purpose is to switch on the UHF B+ and dial light. The 3 back connections are for the lights. The left terminal is the common one, usually has a brown wire connected to it, and the VHF light connects to the right terminal, UHF light connects to the middle terminal. On channels 2-13 the two outside terminals have continuity, when the UHF position is selected, the right terminal disconnects from the left and the center terminal is now connected to the left one. Your switch needs cleaning. It can be opened up and fixed, just be careful parts don't spring out!

[old_coot88]

I wouldn't open the switch up. Just give it a shot of Deoxit or similar. Then let it work a few cycles.

[vortalexfan]

Originally Posted by old_coot88

I wouldn't open the switch up. Just give it a shot of Deoxit or similar. Then let it work a few cycles.

I'll give it a shot.

[vortalexfan]

I'm just curious, but can missing centering rings cause the issues my TV is having with the weird linearity issues?