Designjet T770/T1200 Main Logic Board | 24/7 Support | 260.348.5653
The formatter board has either a network cable or USB cable plugged into it. Next to the connector there are 3 LEDS on the formatter board. They are labeled I, II, III. They will either be solid or flashing. You need to determine what the sequence of the three LEDS are in order to decode the error.
Replace Main PCA board:
To see the youtube videos demonstrating how to remove the covers: