Thanks for the replys!
The wiring diagram picture isnt mine its from Instructables.com, I didnt actually notice the colours of the wires but rather the pin assignments, and the position for power and common/ground is the same as in the diagram
The cameras are definitely in working order because they are still connected to the original surveillance system
and I measured (using a multimeter) the voltage from an rj11 input jack on the back of that unit, therefore the pin assignments for Power & common/ground is know to me and the voltage of 24 Vdc is confirmed also.
I didnt get any picture at all when trying my previous converter on the new Avtech DVR and I tried both remaining wires, one of which must be audio and must be video.
As far as baluns goes it does seem I need them (on DVR end) as I read a couple of threads on forums just before making this thread, one is here
Also on wiki in regards to Baluns, UTP cable and video it says "A balun is also used on the video recorder end to convert back from the 100-ohm balanced to 75-ohm unbalanced."