HP P3015 Service Manual

							Fuser failure detection
The DC controller determines a fuser unit failure, deactivates the FUSER HEATER CONTROL signal,
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.
◦ If the sub 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.
◦ If the sub thermistor detects an abnormal high temperature of the fuser unit.
● Frequency detection circuit failure
◦If a specified frequency of the ZERO CROSSING 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 FUSER TEMPERATURE (FSRTH1, FSRTH2) signals and sends the
FUSER 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 1-12  Fuser-heater control circuit
ZEROX
TH1TP1
H1 FSRD
RLYD
FSRTH2
RL1001
TH2
RL1002
FSRTH1
H1: Fuser heater
TP1:  Thermoswitch
TH1: Main thermistor
TH2: Sub thermistor
Pressure roller
Fuser film
Fuser heater
control circuit Fuser heater
safety circuit DC controller
Engine controller unit
Fuser control circuit
Fuser Relay control
circuit
Frequency
detection circuit
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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 and sub thermistors is abnormal.
● Thermoswitch
◦The contact of the thermoswitch is broken to interrupt power supply to the fuser heater when
the thermoswitch detects an abnormal temperature of the fuser heater.
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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 1-13   Low-voltage power supply (LVPS)
REM24
+3.3V
+5V
+24V
Fuse(FU1002)
Fuse(FU1001)
+24R
/FDOORSNS
+24U
+3.3V
Protection circuit Low-volt age power supply
+24V generation circuit
+3.3V generationcircuit
+5V generation circuit DC controller
Noise filter
Door switch(SW501)
Power switch
(SW240)
Noise filter
Power-switch
control circuit
High-volt age
power supply
Engine controller unit
Fuser
Fuser control
circuit
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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
● Fusing film
Figure 1-14   High-voltage power supply
TR
PRI
DEV
FSRB
Engine controller unit
FILMB
To primary charging roller
To developing roller
Photosensitive drum
Transfer roller
High-voltage power supply
Primary
charging bias circuit
Developing bias circuit Fuser
Fuser filmPressure roller
Transfer bias circuit
Fuser film bias
circuit
DC controller
Cartridge
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							Formatter
Formatter heartbeat LED
The heartbeat LED indicates that the formatter is functioning correctly. While the product is initializing
after you turn the product on, the LED blinks rapidly, and then turns off. When the product has finished
the initialization sequence, the heartbeat LED pulses on and off. For more information abut the heartbeat
LED see 
Formatter heartbeat LED on page 133.
DIMM slots
CAUTION:Single inline memory modules (SIMMs) used in previous HP LaserJet products are not
compatible with the product.
The formatter has one dual inline memory module (DIMM) slot for upgrading the product with more
memory.
To find out how much memory is installed in the product, print a configuration page. For more information
about memory, see 
DIMM cover and DIMM on page 57 .
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							Laser/scanner system
The laser/scanner system receives VIDEO signals from the ECU and the 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 1-15  Laser/scanner system
Formatter
DC controller
Photosensitive drum
Scanning mirror
BD sensorLaser unit
Scanner motor unit
BDI signal
VIDEO signal
LASER CONTROL signal
SCANNER MOTOR CONTROL signal
Engine controller 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
The DC controller uses the laser/scanner and HVPS to form the toner image on the photosensitive drum.
The image is transferred to the print media and then fused onto the paper.
Figure 1-16   Electrophotographic process block diagram
Laser scanner Cartridge
Transfer roller
High-voltage power supply DC controller
Fuser
Laser beam
Engine controller unit
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