Lexmark C750 Service Manual page 158

5060-00x
Step Action and questions
4 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.
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?
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?
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?
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?
9 Check continuity of the AC line cord.
Is there continuity?
10 Check the voltage at J7-5 on the engine board. The
voltage measures approximately +5 V dc.
Is the voltage correct?
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Service Manual
Yes No
Go to step 5 Install the cable
correctly.
Replace the Replace the relay
communication board/LVPS
cable. assembly.
Go to step 7 Go to step 10
Replace the LVPS Go to step 8
assembly.
Replace the relay Go to step 9
board assembly.
Go to step 10 Replace the line
cord
Replace the top Replace the engine
options cable board