Converting a dreamcast VGA box to an RGB signal

[QUAKE]

Hello, long time listener, first time caller.

I have a Dreamcast madness gameware dreamcast vga box, which is the only product I have that has all the pins on the av out port on it.

I just got a gbs8200, and to my disappointment it appears that the games that are not vga compatible (last blade 2) don't actually send a 15khz rgbhv signal through vga.

So I tried to get an rgbc signal out of it, I unsoldered pin 6 to enable "rgb mode,
I unsoldered the hsync and vsync puns and soldered the csync as the hsync pin, following info i found here:
https://gamesx.com/wiki/doku.php?id=av:dreamcastav

the adapter is in vga switch (for pin7 and rgb) and this all goes to the in of a gbs 8200 (stock) but im not getting signal or green flashes.

Where do my mistakes start?

[Endymion]

Confused as to what you did exactly, all you really need to do is remove pin 6 on the box/board side. I desoldered the wire from the board, then using a new strip of wire, tethered it back to the board with a switch. Just modify the VGA cable end if you need it to go somewhere special, that way you will have an unmolested VGA pinout that you can rely on. C sync will be on pin 13 on the VGA side.

[fernan1234]

Some games are locked to specific modes at the software level depending on what kind of cable is detected, and Last Blade 2 may be one of those. I encountered this problem when trying to get NTSC Skies of Arcadia via 15khz RGBHV with a modified VGA cable or box, and it automatically switches to 31khz for the main game. It will only pass a 15khz signal if it detects an S-video or composite cable connected. Supposedly the disc image can be modified to get around this check but I was never able to do it successfully.

[Endymion]

Good point, other games should be tested also to make sure of the work done.

[rama]

I know the GBS 8200 boards very well, and the stock firmware on it doesn't like TV standards 15kHz.
The sync separation unit is not programmed correctly and fails to decode about 30% of common consoles out there.

Unfortunately, I don't have the Dreamcast hardware here to test it, but chances are that the stock GBS firmware doesn't work with it.

[QUAKE]

Confused as to what you did exactly, all you really need to do is remove pin 6 on the box/board side. I desoldered the wire from the board, then using a new strip of wire, tethered it back to the board with a switch. Just modify the VGA cable end if you need it to go somewhere special, that way you will have an unmolested VGA pinout that you can rely on. C sync will be on pin 13 on the VGA side.

That's what I did, but I also removed vsync and hsync and replaced pin 13 from hsync to csync, how else would you csync?

I know the GBS 8200 boards very well, and the stock firmware on it doesn't like TV standards 15kHz.
The sync separation unit is not programmed correctly and fails to decode about 30% of common consoles out there.

Unfortunately, I don't have the Dreamcast hardware here to test it, but chances are that the stock GBS firmware doesn't work with it.

Thanks, I'll update the firmware. I forgot to order the wifi module for it, so I didn't do that yet.

[maxtherabbit]

HV sync on Dreamcast work in 15kHz mode fyi

[darcagn]

HV sync on Dreamcast work in 15kHz mode fyi

Yes, HV sync works in 15KHz and 31KHz mode. That's how all of the 15/31khz switchable SCART devices work, they all combine HV sync to Csync no matter the mode.

[QUAKE]

HV sync on Dreamcast work in 15kHz mode fyi

That’s what I thought!

But using a stock gbs8220 i got no picture

I don’t have a 15khz rgbhv crt to test directly, i was trying to use my pc crt

[maxtherabbit]

HV sync on Dreamcast work in 15kHz mode fyi

That’s what I thought!

But using a stock gbs8220 i got no picture

I don’t have a 15khz rgbhv crt to test directly, i was trying to use my pc crt

stock gbs8220 is ass, it doesn't sync to 15kHz properly IME

get on the CFW train