What a challenge.

Bought a new replacement coil and new diode and installed again in machine.

Also got boards repaired and tested as "GOR" target coil had burnt transistor and chip. Ken Skybeau repaired and tested on his gig so all was good.

Drop targets would still not go up. All targets made sounds when manually dropped and switch behind also makes sound so working.
Volt meter showed 32v power to coil so I grounded the transistor controlling the coil and I got a spark and no action.
I then disconnected grey (earth trigger) wire from solenoid and when this pin is was grounded got a spark and no action again.
Removed new coil and checked new diode. I had no real resistance either ways so tossed over my shoulder and replaced with a new one.
Installed red wire and grounded other side of the coil and targets manually re-set. (progress)

Then double checked the broken wire connection (above) and all good as per Peter's photo.
I took the boards back to Ken for testing and all was perfect still.

Does anyone know how I can find what tells the transistor to fire the coil to re-set the top targets?
I am truly stumped here and would greatly appreciate some advice from the gurus if possible?

When I ground the transistor, the coil fires and all connections on the solenoid board are in good condition. Sockets were all re-pinned recently by Ken also.

Help please!

J.D.
 

If the drop targets are registering that they have dropped and grounding the transistor resets them, then it could be the pre-driver transistor or IC6 the 7408 chip gone, or IC8 7402 chip.
Check these with your multimeter as per the pinrepair guide although the chips can test ok (on the board) even if they are no good.
If in doubt just change them over, this is relatively easy and parts are readily available from Jaycar.
I think for the pre-driver chip you may have to get an equivalent for it, which Jaycar do stock.
I have attached the part schematic showing the solenoid ground path. From what I can find the "GOR" reset is solenoid 4.