I’ve only tested a handful of Neo Geo CD systems, but all had the same strange flaw: csync isn’t connected to the multi-out! This guide shows you how to re-enable csync and explains what the problem was.
Tools / Parts Needed:
You’ll need a few tools for this mod (more info on the tools can be found in the tools section):
– Basic soldering skills.
– Philips head screwdriver
– Razor, X-Acto Knife or box cutter (something really sharp).
– Soldering iron / solder
– Thin gauge wire
This is a fairly easy mod, however it requires cutting traces on your NGCD, so please do this at your own risk!!! As an FYI: This mod gets sync directly from the CXA 1645P chip, which I believe is TTL sync. If you run your systems through an Extron RGB interface (recommended) it shouldn’t be an issue, as those usually clear up any sync issues. I believe adding a 680 ohm resistor will lower the sync to csync-level voltage, however I haven’t tested on an oscilloscope yet!!!
If you’d like to be safe, you could follow this exact same guide, but instead of soldering to the Sony CXA chip, simply connect the wire to the luma output on the S-Video port. If anyone has better suggestions for a proper output, please let me know and I’ll update the guide.
– Start by disassembling your NGCD. Once you’ve removed the top cover, unbolt the circuit board with the output connectors on it. You don’t need to remove the wires, just unbolt the board and flip it over.
– Locate the multi-out connector:
– If you look closely, you can see the composite video signal is routed from the Sony CXA chip, through the csync pin, through the composite video pin (both on the multi-out), then over to the actual composite video output. Use a multimeter to test the connection between the three circled pins below with the arrows points to them; They should all be connected…and if not, stop what you’re doing, as you may have a revision of the NGCD I’m not aware of!! (click the picture for full-sized):
– Use the X-Acto knife to cut the traces before and after the csync pin. Don’t dig too deep, just cut, then test with the multimeter until there’s no connection left on either side:
– Add two pieces of wire to the pins shown below. One wire will connect the composite video line from the CXA back to the composite video pin of the multi-out (and also to the actual composite video output connector, since they’re still linked together). The other wire will connect pin 10 (sync-in) from the CXA 1645P chip to pin 7 on the multi-out. As shown in the picture, “pin 10” is the third from the left, on the bottom row. Click on the image for full-sized view:
That’s it, a simple way to enable csync on your Neo Geo CD systems! Please let me know if you have any questions, or if your NGCD seems to have a different configuration.