Lexmark 7003-050 X340n, Service Manual

Page: 45 / 162

2-24
Service Manual
7003-XXX
Fuser service check (continued)
Hot fuser service check
Note: Ensure correct fuser is installed.
FRU Action
Lamp cable
LVPS/HVPS
Fuser
Unplug the MFP and disconnect the fuser lamp cable plug from the
LVPS/HVPS board connector CN102.
Check for continuity across the fuser lamp by checking across the
connector pins.
• If there is continuity, go to Step 1: Continuity.
• If there is no continuity, go to Step 2: No continuity.
Step 1: Continuity
Turn the MFP on with only the fuser power disconnected.
Measure the voltage at connector CN102 on the LVPS/HVPS. It
should match the line voltage.
If line voltage is not present, see “LVPS/HVPS service check” on
page 2-25 for more information.
Make sure the fuser thermistor is correctly connected to the controller
board. If the problem persists, disconnect the thermistor cable at J15
and check for less than +5 V dc on pin 1. Pin 2 should be ground.
If line voltage is incorrect on pin 1, see “Controller card service
check” on page 2-21 for more information.
Step 2: No continuity
Check the lamp cable for continuity.
• If correct, replace the fuser.
• If incorrect, replace the lamp cable.
Disconnect the thermistor cable from J15 on the controller card.
Measure the resistance across the ends of the thermistor cable. See
“Controller card” on page 5-4 for more information.
Replace the fuser assembly if the resistance is lower than 1K ohm or
shorted.
Note: Resistance measures approximately 240K ohms when cool
and 1.4K ohms hot.
FRU Action
Fuser AC cables
LVPS/HVPS
Fuser
Measure the resistance of the thermistor. The resistance measures
from approximately 1K ohms immediately after printing or POR to
approximately 240K ohms when thermistor reaches room
temperature. (It may take 30 minutes to cool.)
Replace the fuser assembly as necessary.