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,