Here's a
link to a partial schematic for the 802. The DC restorer comes after the video amp so it should be OK. Have you tried doing this using the B&K ?
Set the RF selector to 'IF'
Set the IF frequency to somewhere around 22 MHz
Inject the video signal at the grid of the 3rd video IF (pin 4)
Do you get a picture now ? (you may need to fiddle with the IF frequency). Is it any better ?
Likewise you can work you way back through the 2nd and 1st IF amps.