1973 Zenith B&W Set - Good Audio, Plenty of Snow, No video through VHF

[Electronic M]

Originally Posted by LowHeadRoom

First off,

Thank you for the great advice so far!

The screen is supposed to display video from a vintage game console. I was using NES Tetris and can get full audio from the console.

I have switched between channels 2, 3, and 4 and can get audio through those channels but nothing that even slightly resembles the Tetris game.

I have swept through the fine tuning, turning it left and right for a full sweep. No combination of channel selection and using the fine tuning brings up the Tetris game display.

I have also swept through the AGC control back and forth but do not get anything resembling the Tetris game.

Here are some videos to show how the TV is functioning. I am using the RF modulator this time instead of the NES. It has the same symptoms:

Contrast, fine tuning, vert hold etc:

https://photos.app.goo.gl/Sk8SwCkAQ4RTVSng7

AGC:

https://photos.app.goo.gl/vz4ZQT6KNu5iHCBH8

Snow:

https://photos.app.goo.gl/wtbxbau9DM8WFckZ7

THANKS AGAIN FOR ALL OF YOUR HELP!!

I am thinking it is a bad video detector diode as well.


Thank you,

In your first video the TV had good video on screen (those nearly horizontal bars), but the horizontal hold adjustment was WAY off. You need to duplicate how things were in that video and turn the horizontal hold coil 3 turns in either direction. Whichever direction reduces the number of horizontal bars is the correct direction, you'll need to keep turning it in the correct direction until you get a picture could easily be 5-10 turns. Some Zenith hold knobs have stops that limit rotation to 1 turn...To bypass the stops pull knob ~1/4" out so it's pointer clears the stops...Push it back in once it's adjusted correctly.

I'm guessing you've never experienced a tube TV with the Horizontal hold way off before.