Dim screen running MAME on Sanyo 20EZ

apocalypto

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Hey guys, I'm having a problem with a dim image on my Sanyo 20EZ. Here is my setup:

PC VGA Card (Radeon 9550XL) > 'VGA-to-CGA Converter Card > Sanyo Inverter Board > Sanyo 20EZ

I have tweaked the color adjustments on the neckboard and the inverter board as best I can, and adjusted the brightness pot and screen on flyback. The colors seem to be pretty close to correct, they are just desaturated/washed out and do not pop. The blacks are also not deep and inky.

When connected to my donkey kong junior board, the colors and contrast look awesome, so I think the monitor itself is fine.

I am also running a computer crt monitor through a bypass on the card and the image is very bright and vibrant, as I would expect it to be on the Sanyo.

My theory is that the VGA card is not outputting enough power to the monitor. If I'm not mistaken the card outputs 1V whereas game PCBs output 5V. I am no expert so this is just speculation on my part and I'd love one of you experts to weigh in on this.

Is it simply a case of adding an video amplifier cable such as those sold at Ultimarc.com ?

Also, am I correct in thinking that the games should look as good or better on the Sanyo than a computer crt monitor? I'm using the computer monitor as the benchmark right now.

Thanks guys!
 
Sounds like you need a video amplifier. Most arcade monitors expect to see 2.5 volts to 5 volts for a video signal strength.

Most computer monitors expect 1 volt.
 
The picture should look much more authentic on the real arcade monitor, and the games should look as good or better than they do on the computer monitor. I think you've definitely got a signal level problem, you need some kind of video amplifier. VGA cards typically use .7v or 1v p-p, while arcade monitors are usually higher. It depends on the monitor though.

You'll probably have to somehow amplify the VGA signal. I take it your CGA scan converter doesn't have any options for that?

Also, you're not trying to use some kind of splitter to display the same thing on both monitors, right? That'll make the picture real dim too.

-Ian
 
The picture should look much more authentic on the real arcade monitor, and the games should look as good or better than they do on the computer monitor. I think you've definitely got a signal level problem, you need some kind of video amplifier. VGA cards typically use .7v or 1v p-p, while arcade monitors are usually higher. It depends on the monitor though.

You'll probably have to somehow amplify the VGA signal. I take it your CGA scan converter doesn't have any options for that?

Also, you're not trying to use some kind of splitter to display the same thing on both monitors, right? That'll make the picture real dim too.

-Ian

This should do the job right? http://www.ultimarc.com/vidamp.html

No I'm not using a splitter, the converter card has a bypass vga output and has no effect on the processing that card does. I just unplugged the computer monitor from the card to test and it made no effect on the arcade monitor screen.
 
Great. Thanks Ken and Retro!

If anyone reading this has a video amplifier they would sell, please drop me a PM!
 
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