Star Micronics WinType 4000 Technical Manual page 123

2.3 U4
Step
1 (Initial Check)
Are any parts broken, malformed, incorrectly installed
or different from those listed in the specifications?
• Principle Parts to be Checked:
(1) Fuser assembly, (2) MCU PWB,
(3) LVPS assembly
2 (Check the thermistor in the fuser assembly.) *1
Does the problem occur soon after the power is turned
ON?
3 (Check that power is supplied to the heater rod in the
fuser assembly.)
When the fuser assembly is cold, does the heater rod
light up when the power is turned ON?
4 Does the problem occur while the fuser is warming up? *2
5 (Check that power is supplied to the heater rod.) *2, *3
For 100V models:
For 220V models:
• Measure the voltage while the fuser is warming up
before the U4 error occurs.
6 After the fuser has finished warming up, does the
heater rod turn on and off (light up and go off)? *2
7 (Check the LVPS assembly.) *3
Is a voltage of 4.38VDC supplied between J11-3PIN
↔J11-6PIN?
8 (Check the ON signal for the heater rod.) *2, *3
Is the voltage 0VDC between P/J11-3PIN↔P/J11-6PIN
while the fuser is warming up, and is the voltage
between 0VDC and 4.38VDC after the fuser has
finished warming up?
*1: Since the fuser takes a short time to warm up, determine whether the problem occurs soon after warming up.
*2: To determine whether the fuser is warming up properly, check the operation of the main motor and check
whether the heater rod is turned on or off.
*3: Do not touch the HVPS or any other high voltage components when disconnecting P/J12 from the MCU PWB.
Check
Is a voltage between 90 and 132
VAC supplied between P/J114-
2PIN↔P/J114-3PIN?
Is a voltage between 198 and 264
VAC supplied between P/J114-
2PIN↔P/J114-3PIN?
– 119 –
TROUBLESHOOTING
Remedy
YES
Replace the part or
install the part
correctly.
See section 3.6
Faulty Thermistor.
See step 4.
See step 5.
See section 3.6
Faulty Thermistor.
See section 3.6
Faulty Thermistor.
See step 8.
Replace the LVPS
assembly.
NO
See step 2.
See step 3.
See section 3.5
Faulty Heater Rod.
See step 6.
Replace the LVPS
assembly.
See step 7.
Replace the LVPS
assembly.
Replace the MCU
PWB.