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

[zeno]

Or change to a universal 1 meg pot & leave the tap off. It only
there to tailor the bass to the volume. ( boost bass at low vol ).
If its push-pull on / off Malory made a replacement switch.
Depending on shaft it was a KR8M or KR9M.

73 Zeno
LFOD !

[vortalexfan]

OK so I fixed the power switch, and volume control pot and I got the backlights going but I'm still not getting anything out of the tuner, in fact just to check to make sure the tuner wasn't malfunctioning I disconnected the IF input from the TV to the VHF Tuner and hooked the IF input to the composite (yellow RCA jack) on the back of my converter box and all I get is a snowy picture with a very faint hint of video activity on the screen. So it looks like the IF Section of the TV isn't working quite right, I'm not sure if its bad tubes or dirty tube sockets, or a badly out of alignment IF section (from someone twiddling the IF Cans when they shouldn't have.)

Does anyone have any ideas as to what could be causing a dead (or nearly dead) IF Section on the 23" Zenith TV?

[Electronic M]

Originally Posted by vortalexfan

OK so I fixed the power switch, and volume control pot and I got the backlights going but I'm still not getting anything out of the tuner, in fact just to check to make sure the tuner wasn't malfunctioning I disconnected the IF input from the TV to the VHF Tuner and hooked the IF input to the composite (yellow RCA jack) on the back of my converter box and all I get is a snowy picture with a very faint hint of video activity on the screen. So it looks like the IF Section of the TV isn't working quite right, I'm not sure if its bad tubes or dirty tube sockets, or a badly out of alignment IF section (from someone twiddling the IF Cans when they shouldn't have.)

Does anyone have any ideas as to what could be causing a dead (or nearly dead) IF Section on the 23" Zenith TV?

That's not how it works let alone a valid test. The IF input takes an AM modulated 41MHz ish RF carrier. The yellow composite video output of a DTV box isn't ANYWHERE close to being that.

If you want to inject baseband composite video you can only do that at the output of the video detector diode in the TV (ideal injection site) or points in the video amplifier chain between that and the CRT.

The IF system will ONLY pass IF signal. It will NOT pass composite video.

[vortalexfan]

Originally Posted by Electronic M

That's not how it works let alone a valid test. The IF input takes an AM modulated 41MHz ish RF carrier. The yellow composite video output of a DTV box isn't ANYWHERE close to being that.

If you want to inject baseband composite video you can only do that at the output of the video detector diode in the TV (ideal injection site) or points in the video amplifier chain between that and the CRT.

The IF system will ONLY pass IF signal. It will NOT pass composite video.

Ok, then how do people like Shango and the others that I've seen repairing TVs on YouTube use a composite video signal to diagnose the functionality of the tuner and IF on their TVs when they're working on them?