Thank you

[luRaichu]

I, too, was attempting the same hack on my Sony Watchman FD-510 many months ago. I remember it uses the same chipset as most other 5" B/W sets of the era. The hack for these is to cut the VIDEO OUT trace from the main IC and feed your composite in through there directly to the TV. But when I did this myself I got retrace lines and a dark band on top of the screen.
Never figured out the fix so I bodged it back together and it's sitting in my storage unit now. One of these days I'll have to take another crack at it.

Also, why didn't the manufacturers just include connectors for composite input on these things? My Craig PC570 has them and it works just fine. You can even get composite output from the tiny tuner.