Injecting a composite signal directly into the main board produced this. Funky video and the sync was non-existent. Probably the signal needs to be inverted but there's no polarity switch on the generator.
Injecting an IF signal into the front end of the IF strip proved more successful. Stable video and some sound.
I also tweaked the vertical height and linearity.
So the problem seem to lie with the tuner. Remember these were the only tubes that had been replaced. I'll do the simple checks first - swap out the tubes and check connections.
