George,

to be frank, I reckon it's madness trying to sort this wirng out without even looking at the wiring diagrms and schematics. My guess is you'll blow something up. 

Honestly it's not that hard, the pic I've put in below is ripped form the power wiring diagram;

Spent some time looking at it - preferably the whole diagram - and seeing what bits are what - the plugs are drawn both pictorialy and as they are wired, 3J1 and 3J2 are the ones in your picture. 3J2 is the 6 pin one with two black wires going onto the bottom two pins numbered 6 and 3.  So you can see the colur of the wires - don't rely totally on this as they are for Firepower - and you can see where the wires should be running. Both the black wires run to the negative terminal of the bridge rectifiers - as Nino says you are missing one. The one you've got is under the bunch of wire in the pic - so by following the wires from it, in conjunction with the diagram you'll b get to see where theyshould be going.

The reason the GIO lamps came on is because they are fed in the bottom yellow(ish) area through plug and socket 8P2 8J2.

Grab the power board drawing, it will show you where to measure voltages on the board.

The understanding won't happen immediately and you'll probbaly make a few mistakes, but far less than if you don't try with the diagram at all.  Get all the diagrams in the link I put up, print them out and start scratching notes on them and asking questions - you'll know your machine so much better and probbaly enjoy the experience.