Nudge
I assume you are using the 1077PAL as your IF source...Have you tried connecting it to the first IF of another set that HAS working video and IF to confirm your IF injection source works? Also sometimes the analysts don't have accurate IF freq calibration or a set does not respond where you think it should. I often sweep through the entire dial range. Set the output as high as it will go when injecting IF...If it is too strong it won't do damage and you can turn it down, but if the output ain't set strong enough diagnosis gets tricky.