apple rgb monitor problems

i need some help with an applecolor rgb monitor if anyone can. does anyone know any way of testing this monitor? i have one in the silver-gray colour that matches my mac IIcx yet, i cannot seem to get any video on it. i have tried using both a laser128 and a //c's rgb output into the monitor, but the only thing i can get is a deep blue screen with stable vertical lines with the //c, and a moving blue bar with the laser128 although they both can do rgb output and i was using the same cable. when i tested the monitor with my mac cx which has a 1 bit mono card, i did get video, but was difficult to read, and i got double images of the desktop. i've already tried every control accessable on the monitor too. unlike my vga monitors, this one does not produce a raster screen when no video cable is connected. is there anything else i can try short of round-filing the monitor? david