OK, i'm almost certain this is a power supply issue now (after some great help from one of the guys at Jomac)
The machine has 2 power supplies - one is not giving 12V (the black one) - they were bridged together, so i disconnected the faulty one and terminated the wires going to it.
So the power supply in use (silver one) is giving 11.97V and 5.05V at its output pins, when i test at the pins going into the main board interface, the 5V ones range from 4.96 to 5.02 V (there are about 6). The guy at Jomac said to test either side of the pink coloured capacitors at the end of each IC, when i read there i am only getting 4.86V - which may be the cause of the pixelation....
I pulled all the boards apart and cleaned the connectors with electrical contact cleaner, what else can i do or check to try and get 5V at the board?