Specifications

Chapter 6: FRU Replacement and Fault Isolation Procedures
6-6
6.2.3 Fuser Assembly Problem: Fault code U4
continued
5. HEATER ROD ANALYSIS
Disconnect P/J 111 on the HVPS. Check the following voltages before fault code U4 appears
during the Power–On Sequence: Is there line voltage (90 VAC to 132 VAC or 200 VAC to 240
VAC) between P/J 101–2 and P/J 101–6 in the Fuser Assembly?
Yes No
Go to Section 6.3.6 Temperature Sensor Assembly
Failure.
Replace the LVPS Assembly.
6. Does the Heater Rod switch ON and OFF after Power–On Sequence?
Yes No
Go to Section 6.3.6 Temperature Sensor Assembly Failure. Go to Step 7.
7. LVPS ASSEMBLY ANALYSIS
Disconnect P/J 111 on the HVPS. Perform this check within 30 seconds after switching power
ON. After 30 seconds, the LVPS shuts down due to the no–load condition.
Is there +4.2VDC between P/J11–1 and P/J11–2 on the MCU PWB?
Yes No
Go to Step 8. Replace the LVPS Assembly
.
8. HEATER ROD ACTUATOR SIGNAL ANALYSIS
Disconnect P/J 111 on the HVPS. Perform this check within 30 seconds after
switching power on. After 30 seconds, the LVPS shuts down, due to a no-
load condition.
Is there 0VDC between P/J 11–1 and P/J 11–2 on the MCU PWB during Power–ON sequence,
and does the voltage rise to +4.2VDC when the sequence has finished?
Yes No
Replace the LVPS Assembly. Replace the MCU PWB.