HP P 1100 Service Manual

							Fuser failure detection
The DC controller determines a fuser unit failure, releases the relay to interrupt power supply to the
fuser heater, and notifies the formatter of a failure state when it encounters the following conditions:
●Start up failure
◦If the main thermistor does not detect a specified temperature during the start up process of
the heater in the wait period.
◦ If the main thermistor does not detect a specified temperature during the heater temperature
control in the initial rotation period.
● Abnormal low temperature
◦If the main thermistor detects an abnormal low temperature of the fuser unit during the printing
operation.
● Abnormal high temperature
◦If the main thermistor detects an abnormal high temperature of the fuser unit.
● Frequency detection circuit failure
◦If a specified frequency of the FREQUENCY signal is not detected within a specified period
after the product is turned on.
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							Fuser temperature control
The fuser temperature control maintains the temperature of the fuser heater at its targeted temperature.
The DC controller monitors the FIXING TEMPERATURE (FSRTH) signals and sends the FIXING
HEATER CONTROL (FSRD) signal according to the detected temperature. The fuser heater control
circuit controls the fuser heater depending on the signal so that the heater remains at the targeted
temperature.
Figure 1-9  Fuser-heater control circuit
FSRTH DC controller
RLYD
FREQSNS
AC input
H1TH1
FU1
Pressure roller FSRD
RL101 Engine controller
Fuser film unit
Fuser heater
control circuit Fuser heater
safety circuit
Fixing control
Fuser unit
Relay control
circuit
Frequency detection
circuit
(220-240V model only)
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							Fuser protective function
The protective function detects an abnormal temperature rise of the fuser unit and interrupts power
supply to the fuser heater.
The following three protective components prevent an abnormal temperature rise of the fuser heater:
●DC controller
◦The DC controller interrupts power supply to the fuser heater when it detects an abnormal
temperature of the fuser heater.
● Fuser heater safety circuit
◦The fuser heater safety circuit interrupts power supply to the fuser heater when the detected
temperature of the main thermistor is abnormal.
● Thermal fuse
◦The contact of the thermal fuse is broken to interrupt power supply to the fuser heater when
the thermal fuse detects an abnormal temperature of the fuser heater.
Pressure roller cleaning
The pressure roller cleaning process is initiated by the formatter. The process removes toner that has
accumulated on the pressure roller by transferring it to a sheet of paper.
● The product feeds a sheet of paper after receiving the cleaning command from the formatter.
● Main motor rotation is stopped when the trailing edge of the paper passes through the transfer
roller.
● The main motor rotation is repeatedly started and then stopped. The fuser heater is turned on and
then off at the same interval as main motor rotation.
● Toner adhered to the pressure roller is fused to the paper.
● The paper is ejected from the product.
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							Low-voltage power supply
The low-voltage power supply (LVPS) converts ac input voltage to dc voltage. The LVPS has two fuses
on the PCA. The LVPS 24 V output is interrupted to the fuser and the high-voltage power supply if the
cartridge-door interlock switch (SW501) is in the off position (cover open).
WARNING!The product power switch only interrupts dc voltage from the LVPS. The ac voltage is
present in the product when the power cord is plugged into a power receptacle and the power switch is
in the off position. You must unplug the product power cord before servicing the product.
Figure 1-10   Low-voltage power supply (LVPS)
BSTSIG
FREQSNS
AC input
DC controller
+24V ON/OFF circuit
+5V
+24U
+3.3V ON/OFFcircuit +24V
24VON +24P
+3.3U
+3.3V
+5R
+3.3R
Fuse (FU201)
Fuse (FU101)
Protection circuit Low-voltage power supply
+5V
generation circuit Fuser unit
Cartridge-door switch   (SW501)Engine controller
Power switch(SW502)
+3.3V
generation circuit
+24V
generation circuit High-voltage
power supply
Frequency
detection circuit
(220-240V model only)
Rectifying  circuit
Formatter+3.3UON
+3.3VON
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							Overcurrent/overvoltage protection
The low-voltage power supply has a protective function against overcurrent and overvoltage to prevent
failures in the power supply circuit. If an overcurrent or overvoltage condition occurs, the system
automatically cuts off the output voltage.
If the dc power is not being supplied from the low-voltage power supply, the protective function might
be running. In such case, turn off the power switch and unplug the power cord. Do not plug in the power
cord or turn on the power switch again until the cause is found.
WARNING!If you believe the overcurrent or overvoltage protection circuits have been activated, do
not plug in the product power cord or turn on the product power until the cause of the failure is found
and corrected.
In addition, two fuses in the low-voltage power supply protect against overcurrent. If overcurrent flows
into the ac line, the fuses melt and cut off the power distribution.
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							High-voltage power supply
The high-voltage power supply (HVPS) applies biases to the following components:
●Primary charging roller
● Developing roller
● Transfer roller
Figure 1-11   High-voltage power supply
Primary
charging bias circuit
Developing
bias circuit
Transfer bias circuit
Engine controller
To primary charging roller
To developing roller
Photosensitive drum
Transfer roller
High-voltage power supply
DC controlle r
Cartridge
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							Laser/scanner system
The laser/scanner system receives VIDEO signals from the ECU and formatter and converts the signals
into latent images on the photosensitive drum.
The main components of the laser/scanner are the laser unit and the scanner motor unit. The DC
controller sends signals to the laser/scanner to control the functions of these components.
Figure 1-12  Laser/scanner system
Formatter
DC controller
BDI signal
VIDEO signal
LASER CONTROL signal 
 
SCANNER MOT OR CONTROL signal
Engine controller Photosensitive drum
Scanning mirror
BD sensor
Laser unit
Scanner motor unit
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							Laser failure detection
The DC controller determines an optical unit failure and notifies the formatter, if the laser/scanner
encounters the following conditions:
●The scanner motor does not reach a specified rotation within a specified period of the scanner
motor start up.
● The rotation of the scanner motor is out of specified range for a specified period during the scanner
motor drive.
● The BD interval is out of a specified value during a print operation.
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							Image-formation system
Electrophotographic process
The electrophotographic process forms an image on the paper. Following are the major components
used in the process:
●Print cartridge
● Transfer roller
● Fuser
● Laser/scanner
● High-voltage power supply
The DC controller uses the laser/scanner and HVPS to form the toner image on the photosensitive drum.
The image is transferred to the paper and then fused onto the paper.
Figure 1-13   Electrophotographic process block diagram (1 of 2)
High-voltage power supply
DC controlle r
Engine controller
Laser scanner
Cartridge
Transfer roller
The DC controller rotates the main motor to drive the following components:
●
Photosensitive drum
● Developing drum
● Primary charging roller (follows the rotation of the photosensitive drum)
● Transfer roller (follows the rotation of the photosensitive drum)
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							Figure 1-14  Electrophotographic process block diagram (2 of 2)
DC controlle r
Engine controller
Cartridge
Transfer roller Developing roller
Main motor
Photosensitive drum Primary charging roller
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