Typical VGA lowest sync rate

[kendrick]

Anybody want to talk me into (or out of) hooking up a Sega Model 2 board to a modern VGA monitor intended for a PC? Most RGB implementations won't work on a typical PC monitor due to the lack of true multisync functionality. Most of the monitors you see on a store shelf won't do 15 kHz. However, the GamesX primer says that a typical monitor might go as low as 20 kHz, which would be just fine for a Sega Model 2 board, which outputs 24 kHz on a single synch wire. Drop an LM1881 chip in there to split the two sync signals and I should be playing arcade-perfect Virtua Fighter 2 in my house whenever I want.

Can anybody think of a hole in my reasoning? I'm not risking much... Having a whole pile of 17 inch monitors lying around means that I can afford to blow out two or three of them if I've got it wrong. Any help is appreciated.

-KKC, who might blow some money on a REALLY BIG tube if this works...

[kripp]

Sounds like a good idea to me, I have no clue if it would work or not.

Please let us all know if it does.

Thanks.

[kendrick]

Well, the good news is that one of my monitors actually does do 24 kHz specifically. The bad news is that not all of my monitors fit that description, so if I screw this one up I can't try again. On the plus side, the thing does take a combined composite input signal so I might be able to get away with leaving the LM1881 chip out. If I get this to work, I'll take some pretty pictures.

-KKC, who needs to find some VF2 marquee art and control panel graphics now...

[Darklegion]

I've had one that'll go down to 24khz but it didn't exactly look right (very blurry on certain parts of the screen.).Might have been an issue with the custom modelines for linux I was generating, though.I'd give it a try in any case, I can't see it hurting anything on a modern monitor.

[Guest]

Hrmm...sounds very interesting!  I hope it works

-Segasonicfan

[kendrick]

Well, the good news is that the Sega Model 2 filter board prevented my Virtua Fighter 2 PCB from burning out. The bad news is that I now have a fried VGA monitor. I have many more where this came from, but it's pretty evident that the 24 kHz operating capability of this monitor is way overstated. Therefore, my mission is now to find an appropriately put-together RGB monitor. Or barring that, a nice RGB convertor.

So, no pretty and victorious digital photo today. I battle on.

-KKC, who now must find a subtle way to dispose of the thing...

[kendrick]

Just an update, for anybody who's interested. Turns out the VGA monitor I was using is just fine, and it doesn't like the single, composite synch signal coming out of the Sega PCB. What's worse, it looks like I burned out the 7805 voltage regulator I was using to generate power. This may also mean that part of my board is toast, but I don't know that for a fact.

I have an uncontrollable urge to go on the DigiKey website and order a hundred LM1881 chips, but I think I'll rein that in for now. Rather than spend $200 on a bunch of chips to split the synch signal, I think I'll 'borrow' the RGB convertor from my Neo Geo MVS board and see what kind of composite video it produces on my test TV. If you hear about explosions in Florida, it's probably just me. :)

-KKC, who should, by now, know better than to think he can turn a VGA monitor into ANY kind of useful non-PC display device. Hey, where do people get EGA monitors these days?

[RARusk]

Dude, instead of getting LM1881s and a bunch of chips to split the signal just get yourself an EL4583 chip. If you don't mind dealing with surface mount components you might consider either the EL1883 or ISL59885 chips. These will save you some hassle.