I am not a specialist with that old machines, but it sounds like these lamps may be burnt through.
I would try to change a working lamp (of the same type) into a socket of a lamp, that didn't work before, if that is possible. I don't know how the lamps are assembled on this game, but if it is similar to the modern games you should be able to do that.
Don't forget to turn the power off before!
If that solves your problem you should order some new lamps.
I hope, that helped you a bit