Checker board artifacts with OSSC+Neo Geo AES

[Neo Rasa]

Hi everyone! I think I have an idea of what’s causing these this but I wanted to check here before I started looking into getting different cables and adapters. I was hoping someone here might have experienced this or have a particular cable or modification to the AES to recommend.

So first thing, my stuff: The Neo Geo is a Japanese AES, board revision 3-6. Because it’s a 3-6 the composite traces on it were cut to eliminate jail bars when using an HDMI adapter with it.

Going by what my board looks like based on FirebrandX’s guide ( http://www.firebrandx.com/aespsuguide.html ), I’ve been using this Triad Magnetics 9V 3.5A to power it:
https://www.digikey.com/product-detail/en/triad-magnetics/WSU090-3500-R/237-1442-ND/3094968

My display is a Samsung UN55H7150 1080p, 240Hz refresh with no smoothing/etc. options active

Now that I’ve received my OSSC from here I’ve been wanting to run the Neo Geo AES through it.

The OSSC syncs with the AES, RGBS 264p, 15.73kHz, 59.59Hz:
[img]https://i.imgur.com/OGIGbps.jpg[/img]

Synced up 960X240, 264p, 453034

It works in that I get picture and sound and no lag, and the colors and sharpness with the linex multiplier look great to me, but there’s one major issues:

Using a SCART cable (specifically this one from Retro Game Cables: https://www.retrogamingcables.co.uk/NEO-GEO-PACKAPUNCH-PRO-RGB-SCART-CABLE) with it I get this really bad checker boarding across every game, real or multi-cart:

[img]https://i.imgur.com/JD73eqC.jpg[/img]
[img]https://i.imgur.com/XwzLny5.jpg[/img]

I’ve followed FirebrandX’s tutorial to using the Neo Geo Monitor Test Tool ( https://www.youtube.com/watch?v=offhFgj6_x0 ) to help calibrate this. And I’ve also tried their optimal profile from here: http://www.firebrandx.com/osscprofiles.html and other guides. However no matter what suggested settings or combination of settings I try, the checker board artifacts are still there. This is happening without any extra switcher or anything in the way, it’s going from AES -> SCART -> OSSC -> HDMI directly to my display.

So reading about it more, it looks like what’s happening is that the cable is syncing on composite going by this video (9m22s):
https://www.youtube.com/watch?v=LAlrdCBjUAQ&t=9m22s , and that solution is to use a CSYNC cable instead. But I’m having some trouble discerning the best option for that for the OSSC.

I see that Retro Gaming Cables sells a different board for their SCART cables to do this (https://www.retrogamingcables.co.uk/SYNC-SEPARATOR-CIRCUIT-BOARD-LM1881-COMPOSITE-SYNC-CSYNC-PCB-STRIPPER-EXTRON-MATRIX-SWITCH). Is this ideal or is there a standalone AES SCART cable that already has this capability built in (I wasn’t able to find one)? If I got a component one instead (like this https://www.ebay.com/itm/Cable-8-PIN-DIN-to-RCA-Component-RGBs-CSYNC-Stereo-Neo-Geo-AES-MVS-Supergun/254428914162) would that be more compatible for going from the AES -> OSSC than a SCART cable and typically not have these checker board style artifacts?

Lastly, is there any chance that a different PSU might effect this?

[BuckoA51]

The problem is not every AES outputs clean sync. Using a sync stripper cable won’t cure the problem. There are cables wired for clean sync from the AES, you could try asking Rob at Retro Gaming cables. If the cable still doesn’t work you might need a csync restore mod doing.

I’m not 100% it is just due to the cable either, it maybe you need a more sophisticated RGB bypass doing on the machine, but don’t quote me.

PSU is unlikely to be the culprit. Typically PSU noise manifests itself as moving/wavy interference patterns.

[Neo Rasa]

Thank you for the information Bucko.

I reached out to RGC and Rob did feel a SCART plug with a sync separator PCB in it would do the trick and sent me one. However like you say, after soldering up the new plug the OSSC syncs up but it didn’t fix the checkerboard issue.

I wasn’t going to do the full RGB bypass mod at first because, reading up on it more on neo-geo.com, it seems people generally get a better result by cutting the traces (which was already done) than they do with the bypass mod. But I think trying that is my next step.

Either way if I get it working I’ll post my results here if that’s helpful for people, thanks again!

EDIT!

Success! The RGB did the trick after all and the result is awesome, thank you again!!!

[Author]

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