How can I build a RGB+CSync to SCART video cable for a vintage camera control unit?

Question

I'm an associate professor at a university in Japan, and last year I discovered that my university has two working, vintage Sony DXC-M3A Saticon tube video cameras, along with accompanying power supplies and CCU-M3 camera control units (CCUs).

I'm trying to build a video cable that will run from the RGB+CSync BNC outputs on a CCU to the SCART input on a SCART->HDMI upscaler that I recently purchased. The goal is to get RGB output from the cameras into an Elgato Game Capture HD, which is very picky about which resolutions it accepts through HDMI.

The CCUs output RGB+CSync through four independent 75-ohm BNC plugs. Right now I have a BNC->VGA/15-pin RGB cable, and I was able to use that cable with a Gonbes arcade scaler to get an RGB signal to an LCD monitor, but not into the capture device. I wired my own VGA->SCART cable to go from that cable to the SCART->HDMI scaler, but all I ended up with was a blank screen.

I have some RCA plug to BNC adapters, so I was thinking of cutting off one end of an AV cable (plus one more RCA cable), wiring the ends to the appropriate SCART pins, and then connecting the other end (RGB+CSync) to the CCU, but which pins should I use? Do I need to use a power supply to send the correct blanking signals and aspect ratio selection to the SCART end?

I'd appreciate any advice the StackExchange masses can give me.

Answer 1

OK. I figured out how to do it. Here's my solution for anybody else who's interested in achieving this (although it might actually be just me :-) ).

I cut a three-cable solid-core RCA component video cable in half, leaving me with six RCA plugs plus cables. I used four of the cables, one each for R, G, B, and CSync. I attached the open ends of the cables to SCART pins 15, 11, 7, and 20, respectively. I cut one end off a USB cable and attached the +5V wire to SCART pin 16 (composite/RGB selection), and then made sure to connect all the ground wires on both ends to ground. I connected the RCA ends of the finished cable to the CCU with RCA->BNC adapters, connected the USB plug to a smartphone charger adapter, and then connected the SCART plug to the SCART->HDMI adapter, and finally got a (nice-looking!) RGB signal from the camera.

I might go back and add a 100 ohm resistor on SCART pin 16 to bring the voltage down a bit (the max voltage needed to select RGB with SCART is 3V), but my setup works as is, so maybe it's unnecessary.