as the others have mentioned check these things first.

you will see a 2 pin plug going to the display driver board, check for +5 across these 2 wires (red and black)

On the dmd you will see a 4 pin plug that looks like a plug that plugs into a P.C. hard drive (older style PATA hard drive not the newer SATA hard drive) the 2 centre pins will be GND, on of the outer pins will be +12 the other outer pin will be +5

Even if you do have all the +5 and +12 voltages it is worth getting the upgrade cable just to be sure.