Well I got desperate and swaped the sof transformer with the tfx from FIRE! and well. I now have 16 to 18vdc across the cap. There still is some flucuation in the insert lamps but nowhere near as much. the g.l. is brighter, the flippers have more power. I checked the voltage to the flippers after i changed the tfx, 49 volts.
looks like the tfx has been changed with one out of an older machine at one stage i'm assuming.
I haven't put the tfx in the fire! pin yet but i hope i don't have the same problem.
the fire doesn't have as many inserts so im hopeing it will be ok.

10 points to marty m, he did mention it could be the transformer. well done and mm and thanks to everyone else who gave me some seggestions.