dreamcast to vga box to j-pac to jamma

Hi, I have wired one of the sticks on my super neo 29" to my dreamcast, and now I am trying to get the video working. I read that if you cut the wire from pin 6 on a vga box it will make the vga box output at 15hz, since I have a j-pac I cut that wire (using a meter to locate the right wire) and plugged the dreamcast into the vga box, and the vga box into my J-pac, it displays picture for about 10 seconds when I turn it on, then everything fades to white, can anybody help?

the dreamcast vga is 30hz,

I believe on most of the Dreamcast VGA box, there is a lead that outputs 15 khz. If you can cut the lead to 30 khz, it would force the VGA to output in 15 khz. But that would render the VGA box useless for a PC basically.

I already did the cutting of the wire, I had to run resistors from R, G, and B to ground, works fine now.

<small>[ July 27, 2003, 02:08 PM: Message edited by: Beat_Receptacle ]</small>

Works great, here are some pics if you are interested, comments welcome:

<a href="http://home.houston.rr.com/lcastles/dcpics/" target="_blank">http://home.houston.rr.com/lcastles/dcpics/</a>

looks nice! buttrock

Wow! Great work!! I'm currently working on a PS2 to JAMMA. Hopefully it works. I've heard to use 220microF caps and a sync stripper (gamesx.com) but I've also read some people not getting it to work. I'll have to wait and see...

Hello,

Does anyone know if there is a VGA box that has progressive-scan inputs and outputs 15 khz??? That way I can also get the J-PAC JAMMA Adaptor and I would effectively be able to play most of all the consoles in my Cabinet. I also heard that there is a way to mod your AES console to output RGB. Going to see if Kenny will be able to do that instead of S-video. All I would have to do then is install a small amp with volume control & I'll be set. Any help would be greatly appreciated

I got mine all hooked up, but the picture is VERY bright on my arcade monitor. What am I doing wrong?

I used 220uF caps on each of the R, G, and B lines to the jamma fingerboard.

Are those on the wrong lines? I have the arrow on the cap pointing towards the monitor.

I see someone posted to use resisors to go from the r,g,b to ground? Mine caps are not going to a ground...just inline in the r, g, b color lines.

Thanks
Bill

I Have the same VGA box and it works nice ...just cut the wire of the VGA display (or put it on a switch ...if you still want to play your DC on vga monitor ...) ....and "tada !!" ...you'll get the magic 15khz display on your favorite arcade monitor ...
don't use the "J-pac " as it originally designed to convert a 31khz to 15khz signal ..go straight for a "jamma" adaptor between the VGA box and your arcade cabinet ...


Best results are 100 ohms resistors tied to Ground ....(for each RGB signal)but a friend of mine doesn't use any resistor and manage to get a beautiful picture ...

here is my spec : a electronic project box with 2 hacked DC sticks inside + 12v audio amp ( don't forget ...that the DC has no audio amp built in !!!! (unlike your MVS slots or jamma boards ...)...and a hacked VGA box ....with 3 x 100 ohms resistor ( for the brightness problem) ........and a "jamma" adaptor....

After that ..you are ready to play your favorite DC games on your arcade Cabinet ....... ==> BORDER DOWN, IKARUGA, CASTLE OF SHIKIGAMi etc...etc ...

it costs less .....than a "Naomi" setup !!!!

Neomodus said:

it costs less .....than a "Naomi" setup !!!!

Click to expand...

Does that give you a hard on?

for xtoo_short20x :

sorry , but I don't understand what you mean by "Does that give you a hard on?" ...(I'm not a expert in English )

Best results are 100 ohms resistors tied to Ground ....(for each RGB signal)but a friend of mine doesn't use any resistor and manage to get a beautiful picture ...

^^^^What do you mean by this??? ^^^^^^ tied to ground???

Here is how mine is:

dreamcast vga adaptor------redwire------[220uF cap]-----red solder point on fingerboard

I have the red wire (blue and green are the same way) going from my VGA adaptor to the jamma fingerboard. I cut the red line in the middle and put in the 220uF cap there. so it goes between the red output on the vga adaptor to the red input on the fingerboard with the cap in the middle.

Is that wrong? I am sure this is where my problem is. Can you explain exactly how and where those resistors or caps go? You say tied to ground, but I'm not sure what is meant by that.

I can see the picture on the screen now it is just way too bright.

Thanks a ton! Been working on this for 2 days now...cant wait to get it done! :-)

Bill

For Bill55 :

Sorry , for "tied to Ground" ....as I say ...I'm not a expert in English ...and I think that you'll understand with this link : http://www.jrok.com/hardware/lcd/lcd_panel_fun.html Just take a look at the last pic ( shematic with 75 ohms resistors .... you can try 100 or 75 ohms it depends of your monitor ...)

Just bought some 100 ohm resistors...going to try that now. thanks!

Bill

I got 100 ohm 1/2 watt resistors and did just like that pic shows...In the middle of each color wire (r, g, & b) I cut a spot in the coating on the wire and put a resistor there and ran the other end of the resistor to a ground point on the vga adaptor pcb.

Is that right? I get no video at all now. Before the screen would be white until I plugged it in then I would get a pictures just too bright....now when I plug it in is is immediately black and stays black even after I turn it on. I still get sound so I know it is working.

Do I still need the 220uF caps on each of the r, g, &b lines???

PLZ help!

thanks!!!
Bill

ps- Since you said you are using the same vga adaptor as me (The madness Gameware one) could you take a closeup pic of yours so I can see exactly how you wired it?

Ok...I put the 220 caps back on along with the resistors and I now get a picture again, but it is the same as before I used the resistors.

Does it matter what ground point the resistors go to? Do they all need to go to the same one? Does it matter which way the resitsors go? (can they be backwards?)

Any help is greatly appreciated!

Bill

yo really don't need a jpac since the dc outputs a decent rgb signal....

You can hack directly to the cable, skip the vga box it'self.... only use the vga box's headphone output to drive the speakers....

It's going to be overbright (like the atmoswave). Just use your cab controls to turn down the brightness....

Add a swithch between the 31 khz line and the ground, that way you can still use it on high res monitors...

I am not using a j-pac.

I am using a CD VGA adaptor with the 31khz line cut and forcing it to 15. It is wired directly to a jamma fingerboard.

The monitor controls turn the brightness down but the picture is not correct. Something is not hooked up correctly or the caps or resistors are wrong.

It is not as simple as the controls. The colors are all washed out, but when I turn the brightness down everything just gets dark and the colors still stay washed out even as I turn down the brightness.

Bill