Hi SW

Thanks mate, I now see the adjust screw on the power supply, I don't have a plastic screwdriver, you mean plastic tip right??
I can unplug the power, unplug the board, give the screw a half turn and power it back up and check with the multi meter, would that work OK.
Not sure what sort of board it is, looks pretty old, the cabinet doesn't seen to match any dedicated galalga cabinet I've seen so perhaps is a generic cabinet that could accomodate different games.
As for Jamma, I've been doing a little research, so far have found what Jamma stands for but not sure what my board is, there is an ugly looking adaptor that plumbs the board into the cabinet loom but not sure what that means.
The board does have Galaga written on it in permanent marker but don't know much more about it.
Here is a pic of the board.