Lexmark C750 Service Manual - Page 158

5060-00x Step 4 Action and questions Make sure the communications cable is connected properly to CN3 on the LVPS Relay board. Is the cable installed correctly? Note: The relay on the relay board is connected to +5 V dc from the printer through the communications cable. When the printer is powered on, +5 V dc is sent to the finisher relay board relay coil which energizes the relay and connects primary AC line voltage to the LVPS. Yes Go to step 5 No Install the cable correctly. 5 Check the resistance of the relay coil by measuring between CN3-1 and CN3-2 on the relay board. The resistance measures between 45 ohms and 50 ohms. Is the resistance correct? Replace the communication cable. Replace the relay board/LVPS assembly. 6 Check the voltage on the output options Autoconnect connector Pin 2 located on the top right rear of the printer. The voltage measures approximately +5 V dc. Is the voltage correct? Go to step 7 Go to step 10 7 Check the AC line voltage between CN2-1 and CN2-3 on the relay board. The line voltage should be within specifications for the AC power source the printer is connected to. Is there line voltage at CN2? Replace the LVPS assembly. Go to step 8 8 Check the AC line voltage between CN1-1 and CN1-5 on the relay board. The line voltage should be within specifications for the AC power source the printer is connected to. Is there line voltage at CN1? Replace the relay board assembly. Go to step 9 9 Check continuity of the AC line cord. Is there continuity? Go to step 10 Replace the line cord Replace the engine board 10 Check the voltage at J7-5 on the engine board. The voltage measures approximately +5 V dc. Is the voltage correct? Replace the top options cable 2-124 Service Manual