Connecting a GBS-8200 to the Edge Connector on Donkey Kong

[Sock Master]

I was lazy and didn't even bother checking on a scope, but the sync problem with the GBS 8200 is the GBS 8200 itself.  It seems lots of people are having similar issues when they try to use it with their Amigas or Atari STs.

I tried it after finding this online:
https://ianstedman.wordpress.com/gbs-82xx-experiments/

He also has some other suggestions for improving the GBS 8200 like changing one of the capacitors.

The GBS 8200 expects 3.3V LVTTL levels on sync inputs rather than 5V TTL levels.  5V levels are either overloading the input or the levels are being incorrectly interpreted.  Using a 680 Ohm resistor is actually the lazy way to fix this but it seems to do the trick.   A more proper way would be to use a resistor voltage divider:
https://hackaday.com/2016/12/05/taking-it-to-another-level-making-3-3v-and-5v-logic-communicate-with-level-shifters/

[YesAffinity]

Ah yes, I'm familiar with that wordpress article.  I replaced the linear regulator output with a 22uf cap, as he recommends, but it didn't improve things.  Turning my soldering iron on and off still  causes the GBS8200 to glitch momentarily.

rama, who's been fervently working on the custom firmware, suggests a 100ohm resistor at the input, between csync and ground.  I've got that on mine.  Is that acheiving the same result as your 680R inline?

Also, worth noting, if component input is to be used, the SOG line capacitors are out of spec.  C33 and C35 should be swapped out for 1nf, to avoid component input sync dropouts.  The TrueView 5725 manual even gives a circuit diagram showing that they should be 1nf, but those crazy chinese put 100nf for no good reason.  Unfortunately, they are surface mount and require a bit of extra soldering know-how in order to replace.

[Sock Master]

I think that 100 Ohm recommendation is for TV level sync input, which is different from TTL level sync input..?  but, the end result is probably the same.  All we need to do is shift the voltage levels a bit so it can properly detect the difference between a high and a low signal.

I haven't tried replacing that capacitor on mine but I did do the copper tape shielding mod..  I'm not sure if it made a difference but it can't hurt and it could only make things better, especially considering how marginal so many things on this device seem to be.

[YesAffinity]

It seems I was mis-representing the purpose for the the cap replacements at C33 and C35.

From the shmups custom firmware thread, just to provide clarity:
All source formats except RGBHV (VGA from a PC) benefit from the capacitors swap.
One of the caps is for the 3 RCA input, the other is for RGBS.

The thing I noticed most prior to replacing these caps, was sync dropouts on very bright screens, with component input.  That may never be an issue with DK gameplay.

[danman123456]

ok so I got the following now

nin2jamma->sync cleaner->jrok->Capture device.

1. I too am starting think the sync cleaner does squat for these boards.
2. John (Sock) mentioned he figured out the sync problem and an issue way to fix it.
3. With my setup the Dazzle DVC-100 I have (Super old) doesnt have any issues with the picture (It only works with composite connection) but the Cheap AV2USB2.0 device i had shows a little line on the side. Is that a "sync" issue perhaps? Grrr so frustrating.
4. I have my nin2jamma pots for the RGB signal jacked full on trying to combat some brightness issues with the previous setup. Any thoughts on that maybe the issue with the cheap card vs the DVC? I'm gonna go adjust them back down a bit to see and I'm going to put that 680 ohm resistor on the sync and then if that doesnt work lose the sync cleaner completely.

Check this out to see what I'm talking about:
https://clips.twitch.tv/FantasticGenerousSandstormTTours

Dan

[Sock Master]

3. No idea.. it actually looks like maybe it's a driver issue or the device's de-interlacing process that is adding strange blank line because of a bug in the code.   Try changing or turning off the deinterlacing or scaling settings.

4. I don't have any issues with brightness with my GBS boards.  It kinda seems like it might actually just be a bad cable?

[YesAffinity]

I just got a new capture card - a Magewell Pro HDMI, which I'm happy to report works with direct component connection from the jrok v4.1.  No more need to go through a video processor.

1) And while my cab was off the wall to reduce cabling and such, I gave a quick test to bypassing the sync cleaner.  For component output, there would effectively be no image when bypassing the sync cleaner.  For s-video output, the image is there but constantly losing sync, getting scrambled etc.  I didn't test composite output from the jrok.  I didn't test going to other devices that have historically worked with the direct jrok output, so YMMV.

If you want to try bypassing the sync cleaner, pull the connector that plugs onto the sync cleaner, and jumper the 2 middle pins.  Something like a small paperclip or probably a short piece of solid 26ga wire with the ends stripped would work.

4) I also learned while setting up the new video card that the output from the board, or possibly a result of the NIN2JAMMA, is limited range RGB.  If your capture device, display device, etc. is expecting full range RGB you will never get it properly color balanced.  In my case, there's also a significant amount of noise visible in black areas that also gets cleared up once the range and color balance is correct.  If your capture devices don't give the ability to change this option, OBS will give you the ability.  Set up your capture device in OBS, get it to the point that it displays within OBS.  Go into the device's properties, and you will see a setting for color range.  Change it to 'partial'.  The color space setting of 601 or 709 may also have an effect.

[danman123456]

1. The brightness issue was with the GBS -> VGA Converter -> USB so I just bumped it up all the way and i was able to see everything fine. Output to a monitor was always fine.
2. I plugged the SVideo and Composite cables into the USB cap card with the same results. That solid line on the right side of the screen that would come and go. Like a sync issue that wouldnt completely go away. It was not present in the DVC-100 with either Svideo or Composite which makes think its a sync issue that the DVC ignores or is within "spec" for that card vs the cheap USB adapter? Is there a way to make this sync more consistent vs using the Sync Cleaner output? I'm thinking of a cheap composite->hdmi adapter and the hdmi->composite if I have to try and make it force a signal that will work. Wes mentioned he uses the output from his monitor to feed into his capture card. I'm gonna try to use my damn VCR if i have to.
4. Maybe its my DK somehow? The GBS was stuttering on both the DVC and USB cap card from the GBS even when adding the 680ohm 1/2 resistor. Could be the VGA converter as well I suppose?

Dan

2

3. No idea.. it actually looks like maybe it's a driver issue or the device's de-interlacing process that is adding strange blank line because of a bug in the code.   Try changing or turning off the deinterlacing or scaling settings.

4. I don't have any issues with brightness with my GBS boards.  It kinda seems like it might actually just be a bad cable?

[YesAffinity]

4. Maybe its my DK somehow? The GBS was stuttering on both the DVC and USB cap card from the GBS even when adding the 680ohm 1/2 resistor. Could be the VGA converter as well I suppose?

I'm convinced that DK and probably most Nintendo boards of the era, output a slightly out of spec sync signal.  Socks may know better, but I've done a ton of testing - through the JROK, supergun SCART output to various devices, RGBS direct to various devices.  I don't remember all the results, but they are definitely inconsistent, and below is what I do recall:

1) DK -> NIN2JAMMA -> Supergun SCART -> OSSC - constantly loses sync
2) DK -> NIN2JAMMA -> GBS-8200 RGBS input -> PC VGA LCD screen - good
3) DK -> JROK w/ sync cleaner -> a couple of old school capture devices w/ s-video and composite input - both good (TV-PCIRC PCI capture card and Happauge WinTV-PVR USB)
4) DK-> Nintendo inverter board -> GBS-8200 RGBS input -> VCR direct recording to VHS, and VCR composite pass through to above old school capture devices - good
4) DK -> JROK w/ sync cleaner -> Diamond VC500 USB capture device s-video input - scrambled image, no good
5) DK -> JROK w/ sync cleaner -> DVD0 VP30 component input - good
6) DK -> JROK w/ sync cleaner -> various flat screens, comoponent input - 3 out of 5 work, 2 out of 5 no worky
and most recently, as I described above DK -> JROK w/ sync cleaner -> Magewell Pro HDMI - component input works, s-video input does not; DK -> JROK without sync cleaner -> Magewell Pro HDMI - neither component nor s-video input work

I might have a couple suggestions for improving how the GBS handles the input, based on recent developments with the custom firmware project that has unearthed some poor component choices/implementations.  One in particular is the SMD capacitors on the component sync input are improperly sized from the factory.  The jrok sync cleaner + poor sync implemenation on the GBS (which affects the IC's sync cleaning) could be combining problems.  So, please provide a refresher on what your process chain is, from board to capture device.

[jimbodeanny]

I stumbled upon this thread while looking for information pertaining to a similar issue I'm having with trying to get direct feed from my Nintendo VS PCBs. I know this is a DK forum, but figured you folks might have some insights.

I've been using a JAMMA splitter called "Splitfire" (https://www.arcade-projects.com/forums/index.php?thread/7200-nac-splitfire-jamma-streaming-solution/&pageNo=1) to be able to record direct feeds from my games while playing on the cabinets themselves. I've wired up a harness directly to the device so that I can use it on all of my games, not just JAMMA but classics as well such as Ms. Pacman, Marble Madness, Cheyenne, Gaplus/Galaga 3, Super Hang On, etc.

So clearly it works fine with most games, but I've ran into a snag when trying to capture from my Nintendo VS board(s). I have a Nintendo VS Dual System (aka "Red Tent"). One side is running VS Super Mario Bros, and the other is running VS Dr. Mario. Both games pass through the Splitfire just fine with absolutely no issues on the cabinet arcade monitors. But the signal that runs out of the Splitfire DB15 port appears weak. I know that the colors are inverted, which I correct with OBS via a filter (or using my Framemeister), but they still appear too weak and washed out. The signal almost seems partial/incomplete and faint. If I play with the gain knob on the Splitfire and turn it very quickly, I'll get a perfect picture for a fraction of a second, but that's it. The same thing happens if I unplug and plug the power back in. I've tried using the OSSC as well as the Framemeister, playing with the settings, but can't seem to get it right.

Any thoughts? Perhaps some screenshots/footage would be helpful?

Thanks!!

-Jim

Thanks again and great work!

-Jim

[francoisadt]

I got CGA to VGA : Gonbes CGA / EGA / YUV / RGB To VGA Video Converter

https://www.mikesarcade.com/cgi-bin/store.pl?sku=GBS-8200

What cause input lag, when I boot my machine I do not see boot up screen of the game but
only "Chinese characters" and then the attract screen? No bootup screen before the attract screen?

Which "blue vga" slot are you using the one one one side next to yellow RCA slot or the other side?

Also can one set the cga/vga mode on the PCB somewhere on the CGA PCB?

I got a 12V feed molex from my JAMMA Edge connector harness.


Is it safe to update the firmware on this board? If so how do one do that?

[YesAffinity]

jimbodeanny - have you tried toying with limited range vs. full range settings (assuming you have them) at the capture device?  I find that my magewell pro capture card believes it is receiving a full range signal, but when changing it to handle the signal as limited range, the washed out appearance is corrected.  YMMV

francoisadt - The stock GBS-8200's are not terrible, but they do come with noticeable input lag, among some other shortcomings.  The custom firmware that has been an ongoing project on the shmups forum is your best option to combat lag.  Once modded, the GBS is on par with the OSSC and other no-lag scalers.  The project thread is very long, going back through many iterations, but I'll link it here for posterity.  I suggest visiting the github page for the current iteration of the project, which has all the info you need.

Shmups project thread: https://shmups.system11.org/viewtopic.php?f=6&t=52172&sid=09598b488941b8bd161eec3b36e0210f

Github project page: https://github.com/ramapcsx2/gbs-control

The GBS-8200 manual should answer the rest of your questions: https://www.mikesarcade.com/estore/datasheets/GBS-8200-booklet.pdf
-VGA connector next to the YPbPr connector is input, VGA connector on the opposite side of the heat sink is output
-12v is max.  Many of us users have found that using a 9V source produces more stable results

[francoisadt]

To flash an unknown PCB is too tricky.
I have read the very technical forum post mentioned above and it is too difficult for me to do.
Giving the risk it can forfeit a working PCB into a non-working PCB.

Is there any alternative to GBS-8200? Any other CGA to VGA adaptor card that is better
with no lag input/output?

Is GBS-8200 the best adaptor/converter out there to buy?

Regards
Fdt

[YesAffinity]

You don't flash the GBS.  With the mod, the ESP8266 basically intercepts the lines to/from the original firmware, and the GBS operates from the custom firmware loaded on the ESP8266.

You do flash the ESP8266, but undoing the mod returns the GBS to original operation, and again the native firmware on the GBS is never altered.