HP P2055 Manual

5 Theory of operation
●Introduction
●
Internal components
●
Timing
●
Engine control system
●
Laser/scanner system
●
Image-formation system
●
Pickup/feed/delivery system
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Introduction
This chapter presents an overview of the relationships between major components in the product, and
includes a detailed discussion of the image-formation system. The following systems are discussed:
● Engine control system
● Laser/scanner system
● Image-formation system
● Pickup/feed/delivery system
● Option
Figure 5-1  Block diagram
PICKUP/FEED/DELIVERY SYSTEM LASER SCANNER SYSTEM
ENGINE CONTROL SYSTEM IMAGE-FORMATION SYSTEM
OPTION
80 Chapter 5   Theory of operation ENWW 

Internal components
Figure 5-2  Cross-section of product
1Fuser delivery roller
2Face-down delivery roller
3Pressure roller
4Fuser film
5Fuser
6Transfer roller
7Photosensitive drum
8Laser scanner
9Print cartridge
10Registration shutter
11Tray 1 pickup roller
12Tray separation pad
13Registration roller
14Feed roller
15Tray 2 pickup roller
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16Tray 2 separation pad
17Tray 2
18Duplex re-pickup roller (HP LaserJet P2050 Series Printers only)
19Duplex feed unit (HP LaserJet P2050 Series Printers only)
20Duplex feed roller (HP LaserJet P2050 Series Printers only)
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Timing
Sequence of operation
The microprocessor on the DC controller controls the product operation sequences.
Table 5-1  Sequence of operation
NameTimingPurpose
WAITFrom power-on or the door is closed until the end of
the main motor initial drive.Detects presence of a print cartridge.
STBY (standby)From the end of the WAIT or LSTR period until either
a print command is sent from the formatter or the
power is turned off.Prepares the product to receive print commands
INTR (initial
rotation)From the time...

Engine control system
The engine control system coordinates all product functions, according to commands sent from the
formatter. It drives the laser/sca nner system, the image-formation system, and the pickup/feed/delivery
system.
The engine control system contains the following components:
● DC controller
● Low-voltage power supply
● High-voltage power supply
Figure 5-3  Engine control system
Engine controller
DC controller
High-voltage
power supply Low-voltage
power supply
Formatter LASER SCANNER...

DC controller
The DC controller controls the operational sequence of the product.
Figure 5-4  DC controller
Fuser unit
High-voltage
power supply
Cartridge
Transfer roller AC input
Low-voltage
power supply Motor
Solenoid
Photointerrupter
DC controller
Laser
scanner unit Formatter Fan
Option
Operation panel Switch
Engine controller
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Engine control system 85 

Low-voltage power supply
Figure 5-5  Low-voltage power supply
PWSV+5V
+3.3V +24V
+24U
DOORSNS
SWON
Noise
filter
FET+24P1
Fuse (FU102)
Door switch(SW301)
Power switch (SW1001)
+24V
generation circuit
DC controller
Low-voltage power supply
Engine controller
Fusing control circuit Fuser
+5V
generation circuit
+3.3V
generation circuit High-voltage power
supply
Noise filter
Protection circuit Fuse (FU101)
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ENWW 

High-voltage power supply
Figure 5-6  High-voltage power supply
TR
PR
DV
FB
High-voltage power supply
Primary
charging
bias circuit
Developing bias circuit
Transfer
bias circuit
DC controller
Engine controller
Primary charging rollerCartridge
Photosensitive drum
Transfer roller
Developing roller
Fuser
Pressure rollerFusing film
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Engine control system 87 

Laser/scanner system
The formatter sends video signals to the DC controller, which controls the laser/scanner. When the laser/
scanner system receives those signals, it converts them to latent images on the photosensitive drum.
Figure 5-7  Laser/scanner system
Formatter
DC controller
Engine controller
Scanner mirror
Scanner motor unit
Photosensitive drumBD sensor
Laser unit
LASER CONTROL signal
VIDEO signal
SCANNER MOTOR SPEED CONTROL signal
BD INPUT signal
88 Chapter 5   Theory of operation ENWW