I'm assuming you have the set back up and running, and the jail bars are visible.
Try this:
1) Gently disconnect the IF Input cable from the tuner to the chassis. At the chassis it is very similar to an RCA connector. Power up, jail bars still visible? Power down.
2) Remove the IF Module. Power up, jail bars still visible? Power down. Leave the IF Module out.
3) Drive the video stages with one of your generators. Most generators will block a small amount of DC but to be safe, connect the 50 Ohm video output through a .1 uf or so capacitor to block the DC. Connect to the C1 test point you have identified. Shield to a nearby chassis ground. Power up, adjust video level from the generator, try different patterns, what do you see?
Safety-- This is a transformer based set, so you should be reasonably safe using grounded test equipment, unless something is seriously wrong.
I appreciate my Sencore PR57 everytime I use it
