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

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

Xian Xi

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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.
 

Capitalistix

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Update on this issue: I'm hoping this fix will finally resolve the NGCD CSYNC problem:


Just tried the screwed up RetroRGB mod just now, have a top loader using an insurrection industries Csync SCART cable into an OSSC. OSSC reads "No sync". Looking at that picture from twitter, it looks like that's a completely different board? is that a CDZ?

What can I do here to get a damn picture? @Neo Alec Alec I assume you pulled sync from somewhere else? What is the Luma sync and how can I utilize that to remedy this screwed up mod?

Thanks!
 

Capitalistix

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I tried it before coming here, and finding this thread, obviously.

Do you think you could help me out and explain what you've done to yours to remedy it? I.e. Luma sync?
 

Neo Alec

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It isn't just this thread. It happened over and over again.

It was a long time ago, but I believe I followed the instructions on the bottom of the page I linked.
 

Icelvlan88

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The picture of the mod above, I assume this brings Csync in spec rather than the other one? Do you still need to have the lines cut as the RetroRGB mod did?
 

Neo Alec

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The picture of the mod above, I assume this brings Csync in spec rather than the other one? Do you still need to have the lines cut as the RetroRGB mod did?
The Twitter post from John? I'm not convinced it actually works. I've given up on CSYNC on this system.

For all of these mods, you have to cut the lines to the sync pin, because the boards have composite video connected to that pin from the factory.

If I were to start over, I probably wouldn't mod my console at all. If I needed CSYNC, I would find an external sync stripper solution.
 

Icelvlan88

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I wonder if connecting everything back up the way it was and just using an internal sync stripper is the solution
 

Neo Alec

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I wonder if connecting everything back up the way it was and just using an internal sync stripper is the solution
I've definitely considered it. Not a bad idea.

There are DIY options (some assembly required), but these are pre-made and can also fit in a scart cable:

 
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