A printer lockup indicates a failure in the system and the printer will not respond to external communication commands. If the digital board has failed or locked up, the top row of characters on the LCD may become solid light gray boxes.

Determine when lockup occurs. Perform printer self test diagnostics.

1. If the printer fails these tests it will either present an error message or lockup. Follow message instructions if given, or check/replace the firmware/digital board if it locks up.
   
   
2. If the self test passes, perform print from the on line mode. On line failure is due to data transfer acknowledge (DTACK) failure, buss error (BERR) detection, or by firmware or MPU failure. If the printer previously operated, determine if any changes were made to cause the present problems, otherwise replace the digital board.