I just purchased a used GR 3770 that came with a SC 5500 interface. It did not come with a driver and I couldn't find it on line so I connected using an SC 7500. The document transfers through the interface fine and I can select IF mode on the screen but the Riso will not process it. I have swapped out the Option PCB and cleared the memory with code 97. It makes masters fine using the flat bed. Should I swap out the Image Processor PCB? Or is there something else I can try. (just to note, I also tried with an SC 7700 interface with the same result.)