FOR MEGA DRIVE 1:
what i did here is i cut the trace of pin 7 and pin 3 (composite video) on the PCB near the RGB connector.
now a very strange issue. it got synced on the 1084S-D1 pin 8 + 9 (H-SYNC + V-SYNC together).
after about one minute the screen fades out! first it gets a instable for some seconds, then it fades out, comes back, instable, fades out, comes back etc. seems like a capacitor issue?
i also tried to connect 75 Ohm + 220 µF to pin 11 of the CXA1145 to PIN 7 RGB OUT, NO sync! neither with H-Sync, V-Sync, both together or composite-sync soldered at 1084S plug.
EDIT1: why i cut the "composite video" trace is, because if trace connected the screen stays black. if cut above issue.. works for 1 minute appr. then fades out, comes back etc. strange...
any s-video chances for MD1?