JAMMA Video Output To VGA Monitor

[Majoraslayer]

I'm working on an old arcade machine in which the original monitor has.....well, exploded. So what I would like to do in order to cut down the cost of replacing the monitor with another arcade monitor is to make an adapter that allows for a standard monitor with a VGA connector to be used.

Now, I've done some research and found that the video signal sent from the JAMMA board consists of RGB and a syncronization signal that is compatible with NTSC standards (50-60Hz). The RGB and sync signals have their own unique wires, so splitting them off for VGA connection won't be a problem.

RGB is easy, however a standard VGA monitor has two sync signals (HSYNC and VSYNC) instead of just one. The vertical sync signal is equal to the sync signal being output (50-60Hz), but the HSYNC is roughly twice the VSYNC.

I've tried this project once before by connecting the sync signal to both the horizontal and vertical sync inputs to the monitor. The colors correctly appeared on the monitor, but the image was distorted horizontally.

I was wondering, and I was hoping someone here might know, are the VSYNC and HSYNC signals regular analog clock pulses (i.e. a repeating pattern), or do they depend on the image being sent to the monitor?

The monitor I'll be using has the BNC connections in the back, so it is easy to split R, G, B, HSYNC, and VSYNC. If the sync signals are a repeating pattern, then I should be able to test it out by connecting the sync signals from my computer output to the monitor, and the RGB from the JAMMA board to get it to display correctly. If this does work, I'll also need to know how I might double the frequency of the sync signal (its easy to split off into two).

Any help anyone can provide would be very much appreciated.