Midway pacman screen always vibrating

I had a technician come and he cant seem to stabalize the image on the game .He has the schematics for the game but we cant get the screen stable .Could this be from the 50 hertz transfo instead of the 60 hertz it had in the USA ?or is it from the bulbs .

Thank you for any feedback ?

Pat

It could very well be that the screen is frequency dependent. You can buy a frequency converter for that matter (or build one yourself).