Make sure the fuse holders are not cracked. You'll notice the fuses are fed with 1 maroon/white wire on one side of the fuses and leaves the fuses as 2 separate wires. 1 for the playfield, 1 for the back box ,both via the
LOCK RELAY which I think is the second relay from the coin door on the bottom. The colors FROM the fuse holder to the lock relay vary, could be blue/red, blue/white, blue/red etc., but you should see these connected (thru contacts on the lock relay)
to a solid Blue for the playfield, and a blue/white for the backbox, down on the lock relay. Check for good connections on this relay, clean and or bend contacts as needed. If that's not it, you can follow the blue/white wire from the lock relay thru the jones plugs to the backbox to see if you can find where your loosing power.