Converting from 15 kHz RGB to VGA for an 80's Atari Centipede arcade machine?

Question

I have been hunting around to find a replacement flat panel monitor to replace the honking CRT in a 1980's Atari centipede machine. The existing monitor supports 15 kHz RGB which is not really component video or VGA. I have seen several converters for CGA to VGA, but I am not 100% certain that the CGA has anything to do with RGB.

Does anyone have a recommendation for sourcing the right monitor or converters specifically for going from the Atari 80's RGB to VGA? Really hoping that folks with experience doing this conversion on that vintage of arcade machine respond.

Answer 1

The GBS8220 seems to be the standard way to use modern VGA monitors on old arcade machines. Do you know for sure if your Centipede machine outputs CGA/EGA (digital RGBI), or is it 15 kHz VGA (analog RGBHV)?

Here is a list of flat panel monitors that support 15 kHz analog RGBHV signals. But they often come with caveats, such as you have to fiddle to get the image centered and sized to fill the screen every time you turn it on. Also, the viewing angle may be narrow, depending on the LCD technology used.

And here is a list of video processors that can convert various 15 kHz signals (RGBHV, RGsB, RGBS, etc.) to modern VGA (31 kHz) and HDMI/DVI signals. Some cost as little as USD$30, but if playability is important, look for a video processor that adds as little lag as possible.

Answer 2

I bought a 15" LCD TV two years ago which has RGB inputs, although checking the maker's website just now, I don't think their current models handle it. I would suggest searching for TVs sold to the Caravan / Motorhome or Boating markets. These tend to support multiple input types as they are intended for use in a different location every night - possibly taking different signals.

It is certainly possible to convert RGB to VGA - or HDMI if you wish.

There are a number of electronics shops that sell converter boxes. You will be able to find one near you.
Things to check for are whether the box upscales includes synch (RGBSync) or includes audio. Check too (obviously) that it supports your input frequency. 15kHz RGB is not that uncommon.

Answer 3

Some VGA monitors may sync down to 15.75KHz; if you can find one that will handle that rate, that will be the easiest approach.

There are also some converters that will attempt to convert 15.75Khz video to VGA by doubling every scan line. The result doesn't quite match normal VGA spec, but it's close.

I haven't looked at the Centipede schematic, but I would expect that it might be possible to use a small ARM chip to perform the appropriate conversion if you could get the timing right. Using the FlexIO modules of something like a Freescale KL27, the ARM would need to accept about 250,000 pairs of 32-bit words per second worth of pixel data from the game, and output about 500,000 pairs of words. That should be within the realm of feasibility if the ARM code didn't have to do anything else.