I'm having some trouble finding any information on that model of monitor.
It sounds to me you're describing a 15khz monitor during start with a 31khz signal. It will result in the image being doubled and flickering rapidly.
This monitor is likely a 15khz, or CGA only monitor. You will need to find a way to send it a 15khz signal. You can use an arcadeVGA graphics card, or software such as soft 15khz or groovymame.
First thing for you to do is find more info on your monitor. Do you see any other manufacturers on the chassis or the tube? Names like Wells Gardner, Betson, Billabs, Sanyo, etc.