[old_tv_nut]

No schematic here, but many makes were very similar. If you list out the TTL 74xx chips and connections, you usually find an oscillator that runs at 12 times horizontal or some multiple of that, so there is one stage that has the gate width to generate H sync, burst gate, and gated rainbow bars. Then countdowns to H and V and gates to combine the 12H with H to make H sync. Gates connected to the H and V counters to make crosshatch. Some way to make simple V sync (gated or via multivibrator). A 1-H offset color crystal oscillator (3.5638... MHz) to make the rainbow frequency.

Are the units working? If so, probing with a scope can speed up the process of figuring out what's there. If they're not working, then you would have to trace the connections carefully to figure it all out and draw a diagram.