Response from Jonathan: Peter,

It looks like you are sending the wrong frequency to your arcade monitor. Most arcade monitors run on 15 kHz while PCs typically output 31 kHz. This is why you are getting a double image of sorts. You will need something to convert the signal coming out of your PC to a signal that’s compatible with your monitor. There are a couple of routes you can go to accomplish this.

Our recommended path is to use a video card that automatically outputs the 15 kHz the monitor requires. Ultimarc sells one called the ArcadeVGA which we have used in the past with great success.

Another route you can go is to get a VGA to CGA converter board. Basically you plug the computer into the input on the converter board and then connect the monitor to the output and it converts the signal. Here’s a item on eBay for an example. If you go this route, make sure that you buy one that does VGA to CGA not the other way around. CGA to VGA converters are much more common but they used for replacing arcade monitors with LCDs not for running a computer with an arcade monitor.

Still another option is to use a software program to make the video card output the frequency your arcade monitor is looking for. One of the more popular programs is called Soft-15khz. We don’t like this option because it usually takes it a bit for the software to kick in which means that you are basically sending the wrong signal to the monitor during that time. Even though it probably doesn’t negatively affect the monitor to do so, we prefer a more hardware based solution for this reason.

Hope that helps. Thank you for your question and good luck with your repair.