Using the JROK for the wrong thing

Ven

Kabuki Klasher
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Aug 28, 2000
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124
Okay, I wrote jrok, but I haven't gotten a reply yet, and I'm impatient. I may not get a reply, because I'm using his converter out of spec.

I built a little box. One end has holes for the onboard connectors on the JROK...S-Vid and Composite. The other side is a female Neo-Geo 8-pin DIN socket. I also built a 2 foot patch cord to go between the Neo-Geo AES and the converter, from two male 8-pin DINs and a length of 8-conductor wire I stole from a Saturn RGB cable (snip snip). All DINs are 270 degrees.

Incidentally, someone needs to tell Lawrence to note the difference between 262 and 270, Mega Drive and Neo-Geo, on GameSX, I think. I ruined a 270 plug and gouged my Genesis due to this lack of critical, need-to-know information. -_-

Anyways, everything is wired correctly to the best of my knowledge. The patch cable is just straight through, which is a no-brainer. The socket goes right into the molex connectors that go on the JROK board. I connected the black wire on the 2-pin voltage connector to the shield, and the black wire on the 5-pin video connector to the video ground pin on the Neo-Geo layout.

First time I plugged it in to my friend's AES console, I got a flawless picture, for about 3 seconds. Then it started flipping in various ways, like it couldn't get vertical or horizontal hold, PLUS the colors are completed screwed.

Being the bad person I am, I started fiddling with the plug, making momentary contact with certain pins only. Of course, +5v has to connect, to power the board. But after that happens, if I only connect some of the colors and not sync, sometimes I get that brief picture 'o' perfection again. But it only lasts for a few seconds, every time it happens.

So...any help would be good help. I don't have a supergun to test this on yet (it's still in the works), so I'm not sure what the culprit is. I'm no electrical engineer, so I'm not sure whether it's the thin 24AWG wire from the Saturn RGB cable (but it worked fine on Saturn), a weak +5v signal from the Neo (maybe it doesn't run as strong as an arcade PSU), or just a JROK converter I blew due to using it for the wrong thing.

But it should work just fine by the signals, right? I mean, Neo-Geo is RGB+Negative Sync, like any ol' arcade board. The only thing I've heard is that the Neo AES has weak sync, and that might have something to do with it.

Oh well. If anyone who actually KNOWS electronics, and isn't a hack like me, wants to help, please do. I would have given up on this if I didn't see that 3 seconds of incredible S-Video glory. Now I'm hooked, and I crave a working adapter. And between this and my PC motherboard which just died (right before the release of Jedi Academy, no less), I'm at my wits end. I wish SOMETHING would just work.

- Ven
 

Ven

Kabuki Klasher
Joined
Aug 28, 2000
Posts
124
Sheez, this is like a selling thread. Bump. Anyone that has any suggestions, please help. I'm leaning toward the possibility that the sync is too weak to power the JROK, but if that's the case, I'd love a solution...perhaps some way to boost the sync?

- Ven
 

MKL

Basara's Blade Keeper
20 Year Member
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Perhaps the problem lies in the segment that goes from the Neo A/V port to the jrok. Which pins did you use? Note that on normal RGB scart cables Composite is used as Sync but you should use the actual Sync for the jrok. (how about 5v? You got the right pin?)

This is the correct pinout of the female A/V port (on the Neo):
Code:
        S       R

      C     B     A
            
       G         5v
           GND

S = Sync
C = Composite
A = Audio
 
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Ven

Kabuki Klasher
Joined
Aug 28, 2000
Posts
124
Thanks for replyin'

There's no connection on audio and composite, basically. They just aren't wired. So it's pretty easy to make sure I'm actually using the sync pin. :(

So I used the actual sync and the +5v. I'm pretty sure it's wired correctly. The little length of cable is wired straight through. I just connected the same color wire to the same pin on either side...if I messed that up, I'm truly stupid. I'll go double-check, though.

But you bring up a good point...I used to have an XRGB-2, and when I did, I never checked the official SNK 21-pin Japanese RGB cable to see whether it used c.video or actual sync on the "sync" pin. Plus, when I tried to use the XRGB-2 on my Genesis, it wouldn't even work until I gave it c.video and had it split off the sync itself. I wired it to the Genesis sync pin, and got nothing, which sucked. But it certainly used the Saturn's actual sync pin, with phenomenal results. Maybe I should wire up a Saturn cable and try that. I mean, that thing outputs strong everything...

I've always been confused by this. The XRGB-2 will take either c.vid or sync, so unless I go testing the cable with a multimeter, I can never be sure which it's using.

I wish I could actually find someone that has gotten the JROK working on a Neo home cart system for advice...maybe no one has. I must be the only crazy stupid person trying it.

Wish JROK would write me back...

- Ven
 

MKL

Basara's Blade Keeper
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I'm bumping this old thread because I think I found the solution to the above problem.

Probably Ven's AES had a newer revision board, like this:

mod15a.jpg


While modding one of these recently, I noticed that unlike in early revisions the Sony CXA1145 doesn't send a sync signal to the A/V port. The sync generated by the LPSC arrives at the RGB encoder on pin 10 (sync in) and stops there: there's no trace going off from pin 11 which should be sync out. And the A/V port pin that should be sync (see the scheme in my post above) is in fact the same as composite: you can see the composite trace on the PCB bifurcating at some point and going to both pins. Therefore, when Ven claimed he was using the "actual sync", he was actually using composite. I see no reason why his project of an external jrok shouldn't work with an AES once you're using the actual sync.

The following pics show how to mod a later revision AES to get the actual sync (as well as pure RGB) on the A/V port:

http://www.photobucket.com/albums/v65/nassivera/stuff/AESsolder.jpg
http://www.photobucket.com/albums/v65/nassivera/stuff/AESparts.jpg
 
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norton9478

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I have a early model US AES (11,375)

I take my RGB right off the CXA chip...

I use the RGB out pins and the Synch in pin

and ven, in the future, make sure it's clear what your asking....

I still am confused as to what your asking....
 

Ven

Kabuki Klasher
Joined
Aug 28, 2000
Posts
124
Isn't this post ancient by now? Heh.

That aside...

Thanks for the schematic... I'm glad I now know what was going on there. That would agree with the symptoms I experienced.

My aim was/is to make a converter like the XNEO-1... something universal, that wouldn't require toying with the internals.

I think, to that end, I'll just seperate the sync from the C.Video line, and use that instead. That, or build a small adapter that does that, just for these models of Neo-Geo.

In any case, it sets me off in the right direction. Thanks a lot.

- Ven
 

norton9478

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holy shit i didn't realize that this was an old thread....

getting the sync from the compostite line is probably a good idea.,
 
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