well guys, I finally got my new Fluke multi meter, only took two weeks to get here after I had paid for it.
Tested all the coils and found them to be withing tolerance, except for the drop target reset coil which I knew would be bad, have already clipped off the two yellow wires to this.
Pulled the Driver board out and checked all the transistors but to my surprise these were all within specs.
I'm now back to square one. I replaced the under field fuse with a slo blow of 1 amp, it lasted a few milliseconds more and then blew. Right now I'm at a dead end, not sure where to go  from here.
Should I have totally disconnected the drop target coil instead of just clipping off the yellow power wires??
Any suggestions??

Cheers