Adding composite video input to B&W TV

[maxhifi]

Decided to try adding a composite video input to my RCA 23" B&W from 1965.

Applied video signal to the grid of the 6AW8A video amp as per this link

http://antiqueradio.org/A-V_AdapterForVintageTVs.htm

Rather than cut any wires just pulled the second IF tube. Picture looks sharp but has the dot pattern caused by the colour signal. Got to try this again with the S-video luma signal, or find a way to filter it out.

Sound is a bit more tricky, there's no audio preamp stage, just crappy quadrature detector straight into a 6BQ5... Will need to add a preamp somehow, maybe a 6C4?