RGB CSYNC Mod (Neo Geo AES)
Some revisions such as the 3-5 and 3.6 have composite wired to the CSYNC pin for RGB output.
An easy test is use your multimeter to see if the COMP and CSYNC pins have continuity.
If they do, you can perform a simple modification to restore CSYNC to the pin.
Having composite wired to CSYNC can cause the RGB receiver such as OSSC to not even recognise a valid RGB signal sometimes.
If you find your CSYNC pin is outputting composite video (it has continuity to the Composite Video pin on the AV port on CSYNC), then simply cut the trace coming out of the CSYNC pin on the AV port, and solder a 75 ohm resistor from this isolated CSYNC pin, directly to the CXA pin CSYNC OUT.
When routing to the CSYNC OUT pin of the CXA chip, make sure to run the wire away from any RGB data lines and clocks.
Now you should have a perfect CSYNC output on the CSYNC pin.