Dreamcast VGA Box

Started by Logistics, January 30, 2006, 06:36:49 PM

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||Posted here since nobody noticed this question in a reply I made in General.||

I bought a real Sega box, and on my old 20" SGI monitor, it's kind of dark.  Could changing the capacitors in the DCVGA box help brighten things up?


I'd suggest trying another monitor...it may be that the one you're using is simply too crap

If you're looking to experement then try omitting the caps alltogether. Changing their value/type won't fix a thing.


I don't have that monitor, anymore but I have a SGI equivalent I can try the VGA box on as well as an HDTV.

I will likely post a new thread comparing VGA cables as I read about situations where display issues were rectified by using a VGA cable which equips the H/V signal lines with 75-Ohm coax as well, and I just ordered a Calrad cable which is built in this fashion.



A  vague memory arises in my feeble little brain. Didn't the official Sega VGA box for the Dreamcast operate only with a few specific monitors because it didn't comply with all the proper voltage specifications? I remember a conversation about why third-party VGA boxes were so much bigger and seemed to contain so many more components, which turned out to be bits meant to deliver the full five volts expected by the monitors at the time.

Any chance you can get your hands on a third-party box for comparison purposes? I bet one of those drives your SGI monitor just fine.


I don't remember anything of that nature (though I wouldn't be completely surprised if it was true).  Also, I've never yet used my Sega-made VGA box on a monitor and failed to have it work properly, but that's probably a sample set of a dozen monitors, so maybe not so useful.


Hilariously, all the Google search results are either GameSX posts, or posts on other boards that cite GameSX. This is the relevant one:


In short, the VGA spec specifies TTL voltages, which means everything has to be exactly five volts. Everything that comes out of a straight-through VGA adapter cable for the Dreamcast may end up outputing only 3.3 volts, which most VGA monitors will accept. The ones that don't will exhibit unpredictable behavior, which is why the third-party boxes generally included extra circuitry to mess with the synch and to regulate the voltage. No telling if this is your problem, but it's worth exploring.