Thanks Ken
Will see how I go tracing a short.
I did note that once a new fuse is fitted, and I power it up I can hear a solonoid firing and then the fuse blows, I can't get up from the power point quick enough to see which coil is firing, (someone has removed the mains switch that usually lives under the cabinet). 
Get yourself a powerboard with individual switches and with the playfield up flick the switch while standing next to the machine.
If you want a bit more time to see you could put a 2 amp slo-blo in there and quickly flick the switch on then off.
This will probably allow you a few goes without blowing the fuse but you should see which coil is firing.
Also check none of the diodes on the drop target are bent over and earthed out, this can cause heaps of screwy sh?$*t.
I you can see the general area where the coil is you may have to disconnect all the coils in that area and re-connect them one by one.
