GBS 8200/8220 CFW Project

[Iraito]

I have been using this unit for 5 years with all possible consoles, i only added the hdmi kit, yes i did most mods.

[Gunstar]

I have been using this unit for 5 years with all possible consoles, i only added the hdmi kit, yes i did most mods.

No clock gen mod? Are you using an ESP for custom firmware?

[Iraito]

yep

[Gunstar]

yep

Ask Shane/Electron Shepherd if his kit works without the clock-gen mod. Also try removing the 100 ohm resistor and then test 480p upscaling again. What setting is selected in the Control menu? Downscaling isn't on by any chance?

[Iraito]

i'm waiting for his answer, taking the resistor out made no difference, no downscaling.

[Iraito]

Still no answer but i think it's the lack of clock gen, the signal is there but the hdmi kit doesn't output it correctly.

[SMLMcKenzie]

Bit of a longshot but has anyone in the UK used the following RGB SCART cable with their GBS Control?

https://www.ebay.co.uk/itm/203593632758

I asked the seller if it would be compatible with my Super Famicom and my GBS Control (Ali express pre built) but they told me they were unfamiliar with the GBS Control.

[Gunstar]

Bit of a longshot but has anyone in the UK used the following RGB SCART cable with their GBS Control?

https://www.ebay.co.uk/itm/203593632758

I asked the seller if it would be compatible with my Super Famicom and my GBS Control (Ali express pre built) but they told me they were unfamiliar with the GBS Control.

Cable should be fine as it's CSync which is preferred over Luma/Compos.Sync as you don't need the additional 100 ohm resistor on the GBS, and it'll have the 470 ohm resistor to lower the voltage inside the SCART head. If anything would cause an issue it would be the the pre-built and how it handles the various types of syncs.

[SMLMcKenzie]

Thanks!

[Calab]

I'm not sure where to take this, but it involves a GBS 8220 with the GBS Control mod...

I just installed the GBS Control mod onto my GBS 8220 board. It is working well with my Atari ST as well as my TMS-RGB modded TI-99/4a and Coleco ADAM.

I also have a TRS-80 Coco 3 that has analog RGB output, but does not work with the GBS 8220. When the Coco is directly connected to a 15Khz capable monitor, I get a decent picture. Unfortunately, I can't use that monitor for my Coco 3.

I would like to use the GBS 8220 to convert the Coco 3 RGB to a 31Khz VGA signal. The Coco 3 outputs RGB, H Sync and V Sync (I believe both syncs are positive). I've also added a mod with a couple of XOR gates (I believe it was a 74LS86 chip) to produce a composite sync. I am not sure what signal levels the Coco 3 uses, but the fact that I do get a picture on a 15Khz capable monitor shows that they can't be too far out of the normal spec.

What I'd like to know is...
- What signal levels does the 8220 expect to see on the VGA input connector?
- Can the 8220 use separate H sync and V sync signals instead of a composite sync? If so, can I use the VGA connector, or do I need to use one the other input connectors?
- Does the 8220 expect negative or positive sync signals?
- Has anyone successfully used an GBS 8200 or 8220 with a Coco 3? Was there anything special you needed to do so?

Any suggestions are more than welcome.

[kitty666cats]

Bit of a longshot but has anyone in the UK used the following RGB SCART cable with their GBS Control?

https://www.ebay.co.uk/itm/203593632758

I asked the seller if it would be compatible with my Super Famicom and my GBS Control (Ali express pre built) but they told me they were unfamiliar with the GBS Control.

It should be fine. That guy’s cables are just as good as any of the big brands, he’s been around forever and doesn’t get enough credit. Rob Webb. http://consolegoods.co.uk

If you set your search results to worldwide, the dude has two eBay accounts for some reason & you can get the cables a little cheaper from one of the two accounts. He uses the same photos

[SMLMcKenzie]

It should be fine. That guy’s cables are just as good as any of the big brands, he’s been around forever and doesn’t get enough credit. Rob Webb. http://consolegoods.co.uk

If you set your search results to worldwide, the dude has two eBay accounts for some reason & you can get the cables a little cheaper from one of the two accounts. He uses the same photos

Thanks!

[Gunstar]

I'm not sure where to take this, but it involves a GBS 8220 with the GBS Control mod...

I just installed the GBS Control mod onto my GBS 8220 board. It is working well with my Atari ST as well as my TMS-RGB modded TI-99/4a and Coleco ADAM.

I also have a TRS-80 Coco 3 that has analog RGB output, but does not work with the GBS 8220. When the Coco is directly connected to a 15Khz capable monitor, I get a decent picture. Unfortunately, I can't use that monitor for my Coco 3.

I would like to use the GBS 8220 to convert the Coco 3 RGB to a 31Khz VGA signal. The Coco 3 outputs RGB, H Sync and V Sync (I believe both syncs are positive). I've also added a mod with a couple of XOR gates (I believe it was a 74LS86 chip) to produce a composite sync. I am not sure what signal levels the Coco 3 uses, but the fact that I do get a picture on a 15Khz capable monitor shows that they can't be too far out of the normal spec.

What I'd like to know is...
- What signal levels does the 8220 expect to see on the VGA input connector?
- Can the 8220 use separate H sync and V sync signals instead of a composite sync? If so, can I use the VGA connector, or do I need to use one the other input connectors?
- Does the 8220 expect negative or positive sync signals?
- Has anyone successfully used an GBS 8200 or 8220 with a Coco 3? Was there anything special you needed to do so?

Any suggestions are more than welcome.

That's interesting, I would have thought upscaling 15khz RGBHV on the GBS would be okay, it's downscaling where it doesn't like H/V sync. It works fine with 0.7vpp on RGB and H/V TTL sync voltages, not sure about positive (or mixed) polarity but I'm pretty sure it's okay with negative (VGA). Maybe someone can confirm other polarities? quick google says the 74LS86 would output negative composite sync (CSYnc) and requires a 470 ohm resistor on the CSync out of the IC to bring down safe/~700mv levels, although I vaguely remember someone saying it worked without the resistor too. Strange it's not working on the GBS in that configuration either.

It does the following with only one IC (74LS86), two resistors and two capacitors:
Combines horizontal and vertical sync signals to a composite sync.
Inputs can be positive or negative polarity sync signals. It autosenses them.
Outputs a "standardized" negative composite sync (or positive with a little modification).

Source

470 ohm resistor source:

[Calab]

It does the following with only one IC (74LS86), two resistors and two capacitors:
Combines horizontal and vertical sync signals to a composite sync.
Inputs can be positive or negative polarity sync signals. It autosenses them.
Outputs a "standardized" negative composite sync (or positive with a little modification).

That looks similar to what I put together, but used the other two XOR gates to invert the polarity to positive.

I have parts on the way to try a passive method to combine the syncs that I'm going to try. I'll post the results once I've got the parts together and tested.

[Iraito]

yep

Ask Shane/Electron Shepherd if his kit works without the clock-gen mod. Also try removing the 100 ohm resistor and then test 480p upscaling again. What setting is selected in the Control menu? Downscaling isn't on by any chance?

So i got an answer and even though he hasn't ever seen an issue exactly like mine he thinks it might be an unstable input coming to the GBS, possible?
I have been using this dreamcast for a while and i never had issues by outputting in VGA, it all started with the hdmi kit.

[Iraito]

I tried yet another input type, ps2 component, different yet similar issue.

[Iraito]

After a bunch of experimentations i think i was at least able to pin point the issue https://imgur.com/a/VuPRiyz

If the pr/v is lowered the green noise vanishes but the distortion stays and if i cycle ram up to 185mhz the noise lowers a lot.

[Calab]

That looks similar to what I put together, but used the other two XOR gates to invert the polarity to positive.

I have parts on the way to try a passive method to combine the syncs that I'm going to try. I'll post the results once I've got the parts together and tested.

Well... no luck. I don't get any picture with the passive sync combiner, even going to my Dell U2410 monitor that supports 15Khz. So that was a bust... this is the circuit I used, but substituted a 2N222 for the 2N3904:

Spoiler

[Calab]

Well... no luck. I don't get any picture with the passive sync combiner, even going to my Dell U2410 monitor that supports 15Khz. So that was a bust... this is the circuit I used, but substituted a 2N222 for the 2N3904:

Spoiler

So, while troubleshooting this, I found that the RGB cable I was using did not work properly. I wired up a new cable and the picture straight to the monitor was much better. I used the 74LS86 mod again to combine the two syncs and connected through the GBS8220. It works!!!

My original issue with using the GBS8220 was that I needed to combine HSync and VSync. Doing so was hampered by a flaky RGB cable. Once I replaced the cable, everything worked like it should have.

[Ged]

Hi everyone, I did my build of the GBS-C: clock generator, 4 parallel caps and also the 22uF in place of C11. I'm experiencing some strange issues.

SNES NTSC and PAL are working correctly (PAL's image is jumping a bit in the beginning of a game, but it seems better without FrameTime lock).
AV Famicom: I can hear audio but the image is extremely dark, almost black. I can only see some faint, almost invisible lines. This is with an NTSC cable, the same one I use with the CRT without issues.
PS2 PAL: no image and no sound at all, even though the PS2 is correctly set to RGB mode.
These are all tested and working consoles. I tried to decativate the clock generator, force 50/60hz on HDMI and also tried on another monitor, in order to rule out any issue related to my TV.

On the console log it seems that it's picking up the signal correctly, but I can provide more detailed logs to anyone willing to help.

Another weird issue I noticed, is that the web GUI stops working if I plug in the video cable of the AV Famicom or the PS2. As soon as I unplug the video cable, the GUI becomes usable again.

Thanks a lot.

[mojirui]

Hello, guys! Is possible to use 0.1mm copper wires to do the soldering of the project? Are they too sensitive or enough? I'm thinking of using them because of the cleaner aesthetics they would provide. Also, does anyone have any idea how I can bypass the audio from the input to the output of the board without using those ugly adapters that cross the board? In other words, I just want to bypass the audio to my VGA -> HDMI adapter without it getting too cluttered. Thanks everyone!