Neo Geo CD CSync Mod?

Burning Fight!!

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Hi, my GBS-8200 (Control mod) really struggles to sync with my Neo CD so to remediate that, considering the Neo CD outputs Composite instead of CSync on pin #7, I recently tried to mod my Neo CD to actually output CSync on that pin as per instructions on https://www.retrorgb.com/ngcdcsync.html, but all I got was an extremely dark picture. The image basically starts normal but gets very dark in 1 second, and I can reproduce this by cutting and restoring connection to sync (Scart #20) on my GBS-8200 (with a GBS Control mod and a SCART connector daughterboard).

NGCDcsync04-small.jpg


This video I stole from a blogpost somewhere exemplifies this perfectly (note the Data East logo screen starting ok but dropping all color brightness real fast): http://retro.supermegabyte.com/wp-content/uploads/2019/03/vid.mp4

I ended up plugging pin #7 to the luma pin on the S-Video connector and sync seems more stable and definitely more clean (I had jailbar on solid colors like the top score screen on Super Sidekicks 3 with the green bg), but it's still not perfect as I have to wrestle my GBS-Control until it actually syncs properly.

Q: Is there anything I'm missing (resistor, cap) in the bridge between the through hole and CXA1645P's pin #10 for this to work? RetroRGB isn't too clear on this and just shows both points connected through a wire and that's it.

Bonus Q: For those with a modded GBS8200, how's your experience with the Neo CD if any? Are you also getting sync issues or is it just me?
 
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Neo Alec

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Yep. I ran into the exact same issue. The instructions on that page need to be updated or removed because they don't work. I also posted instructions for the CDZ here that have the same issue. It works fine on the Framemeister, but I ran into the darkening/brightening issue on a CRT.

Changing to sync on luma solved the issue. I still need to correct this on my CDZ.
 
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Xian Xi

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The 8200 synced fine when I did it with anything Neo. Are you holding down the sync button? I had to do it twice for it to be perfect.
 

Neo Alec

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It's not just the 8200 though. The sync signal using that csync mod is unstable.
 

Burning Fight!!

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The 8200 synced fine when I did it with anything Neo. Are you holding down the sync button? I had to do it twice for it to be perfect.

It's a modded GBS, those don't operate like the vanilla board so no button action. The modded GBS seeks sync automagically and I guess it doesn't like the Neo too much haha. Check out gbs-control when you have the time, it really becomes a beast of an up/downscaler for the asking price after the mod.

I guess I'm keeping Luma sync unless a complete diagram for the mod pops up, it outputs a GORGEOUS image on it for me. I do have to cut off and on sync 2 or 3 times everytime before the GBS takes the hint, but otherwise it's pretty damn good... and I'm really surprised it solved jailbar problems I was having.
 

Xian Xi

JammaNationX,
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If you do the Csync mod, I’d add a 220uf cap before the resistor.
 

Xian Xi

JammaNationX,
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Might be best to run it through a buffer then.
 

Neo Alec

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Any recommendations? The Framemeister adapter has a sync stripper built in, but not sure my options for an analog CRT.
 
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