Lexmark T620 Service Manual - Page 115

4069-5XX/7XX FRU 2 System Board (No buttons work) Action Check the voltage at J16-2. The voltage measures approximately +5 V dc. If incorrect, replace the system board. If correct, check the continuity of the operator panel cable. If incorrect, replace the cable. If correct, replace the operator panel assembly. Operator Panel Display Service Check SERVICE TIP: The printer has detected a problem with the system board, operator panel cable or operator panel assembly if POST does not complete and the printer emits 5 beeps and stops in a continuous pattern until the printer is turned off. The operator panel cable is an individual cable on some printers and a combination cable assembly with the cover switch cable on later models. Note: If the operator panel is operating properly except for a PEL or a few PELS missing or broken, run the "LCD Test" on page 3-14 from the hardware tests before continuing with this diagnostic service check. FRU 1 Operator Panel Cable 2 Operator Panel Display blank, 5 beeps, LED Off 3 Operator Panel Display blank, 5 beeps, LED On 4 Operator Panel All Diamonds, no beeps Action Check for proper installation of the cable at the system board (J16) and at the operator panel. Check the continuity of the operator panel cable. If incorrect, replace the cable. Check the voltage at J16 on the system board. It measures approximately +5 V dc. If incorrect, replace the system board. If correct, replace the operator panel assembly. Check for continuity between J16-4 and ground. If correct, replace the operator panel assembly. If incorrect, replace the system board. Replace system board. Diagnostic Information 2-87