[solved] Dreamcast in my Astro City (Hacked VGA box)

So Ive been reading up on this and had a Dreamcast VGA box laying around so I decided to give it a shot last night. From what I have read you need to remove the 6th pin on the dc cable to allow the 15hz signal to be sent to the arcade monitor.

So I removed the pin, cut off the VGA connector and soldered RGB to a Jamma Fingerboard. I can get a picture however it's pretty distored and rolling I also read that you may need to Twist the Vertical/Horizontal Sync wires and solder that to the synch pin on the fingerboard, I tried that, I also tried vert synch and hori synch seperate but the same results. I also have some 220uF Cap's lying around which I also heard may help anyone who's done this could lend some insight would be appreciated.

Thanks!

I've not messed with the Dreamcast in a while, but 15khz RGB is available right on the connector, as is composite sync. You shouldn't have to use any of the VGA box electronics to do this - I think you really only need the cable that plugs into the Dreamcast. The 220uf capacitors are to filter out the DC offset from the video signals - without them the picture will be dim and crummy. Those caps are only used on the video lines, not on the sync. Composite sync is available on the Dreamcast pin 10 - connect that straight to the arcade monitor's sync.

Actually, come to think about it, I have no idea what's actually in the VGA box, beyond a sync seperator and some caps... The Dreamcast already handles the VGA framerate...

-Ian

ok ill try that tonight. I know im close, I just gotta get it going once i get a stable picture ill worry about adding the caps to the RGB lines

Edit**

Also I heard it's not safe to run your jamma setup without sufficient load to the Powersupply as it could burn out overtime. would running the +5V or +12V line from the DC VGA cable to the jamma fingerboard give it enough load?

Why not just purchase the ultimarc Dreamcast to arcade monitor adapter? I have one and it works flawlessly.

are you running through a jpac or anything? i wanna be able to swap to jamma when needed

Biohazard53 said:

Also I heard it's not safe to run your jamma setup without sufficient load to the Powersupply as it could burn out overtime. would running the +5V or +12V line from the DC VGA cable to the jamma fingerboard give it enough load?

Click to expand...

Well, in general, switchmode supplies don't like being run without a load. Newer supplies simply won't start without a load, others will work just fine, as they have minimum loading built in. In any event, "unloaded" isn't an ideal configuration to let a switcher run in. But, since you don't need the power supply when running the Dreamcast, you can disconnect it or pull out the power supply fuse in the cabinet (if it has one).

Don't connect the Jamma power supply to your Dreamcast - those +12v and +5v pins are outputs - the Dreamcast supplies those voltages.

Edit: if you really do want a load on the supply, wire up a car taillight bulb to the +5v rail - that should be enough load for the supply. That's what I do when working on power supplies on the bench.

-Ian

Got it working! thanks a bunch Retrohacker it was actually my stupidity, I assumed RGB colors from the dreamcast cable matched up to RGB on the finger board but it was that yellow(wire) was Blue, green(wire) was red, blue(wire) was green oh and I also forgot to ground the video once I did that I added the caps and got a nice clean clear 15hz picture,

edit* meant to say Capicators

So no video amp is needed? The picture is plenty bright without fiddling with the monitor?
I assume you just added the 220uf caps to the RGB lines and your good to go.

I have been working on a JAMMACAST on and off here for a while now, although I want my DC to be powered by the JAMMA connector and all fit inside the orig DC shell.

no video amp needed, and your correct I ran the 220uF cap's on each of the RGB lines