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.

The best way to find out is to start checking the pins on the connector with your multimeter.
With the machine OFF and the connector removed from the board, check the wires one by one and match what you get to a JAMMA pinout diagram.
Start with the 5V and 12V power and  it won't take you long before you can see if its wired to JAMMA or not.
There are some 28/56 pin variants out there that are nothing like the JAMMA pinout so it will be pretty obvious.

Give the contacts on the board where the connector goes a good clean with a regular white eraser, then have another look at the connector pins, if they are not shiney, it may pay to change over the harness or connector.
You can get all sorts of wierd stuff happening when you have dodgy connections, even check any other connectors the machine might have.

With the ready made JAMMA connectors around today it almost doesn't pay to get out a soldering iron.