HP Laserjet 5 Service Manual

							Static Eliminator Teeth (located in front of the transfer roller)
Cleaning Spilled Toner
Defective toner cartridges can develop leaks. In addition, after a paper jam has
occurred, there may be some toner remaining on the rollers and guides inside the
printer. The pages that print immediately after the jam may pick up this toner.
Clean spilled toner with a cloth slightly dampened in cold water. Do not touch the
Transfer Roller with the damp cloth or with your fingers. Do not use a vacuum
cleaner unless it is equipped with a micro-fine particle filter.
NoteIf toner gets on your clothing, use cold water to remove it. Hot water sets toner
stains into fabric.
Figure 4-2
4-8 Printer Maintenance 
						

							5
Functional Overview
Contents
Basic Printer Functions .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . . 5-3
DC Controller/Power System . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . . 5-4
Print Engine Control System .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . . 5-5
Power System (on DC Controller PCA) .  . .  . .  . .  . .  . .  . .  . .  . .  . . 5-6
Formatter System . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . . 5-8
CPU . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . . 5-8
Read Only Memory (ROM) .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . . 5-8
Random Access Memory (RAM) . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . . 5-8
Parallel Interface .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . . 5-8
Control Panel .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . . 5-9
Resolution Enhancement (REt) . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . . 5-9
EconoMode . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . 5-10
Memory Enhancement technology (MEt) . .  . .  . .  . .  . .  . .  . .  . .  . 5-10
Enhanced I/O .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . 5-11
Page Protect . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . 5-11
PJL Overview . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . 5-11
Image Formation System . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . 5-12
Toner Cartridge . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . 5-13
Step 1: Drum Cleaning . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . 5-13
Step 2: Drum Conditioning . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . 5-13
Step 3: Image Writing . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . 5-13
Step 4: Image Developing . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . 5-14
Step 5: Image Transferring . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . 5-14
Step 6: Image Fusing .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . 5-14
Paper Feed System . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . 5-15
Paper Jam Detection .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . 5-18
Basic Sequence of Operation . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . .  . 5-19
Functional Overview 5 - 1 
						

							5 - 2 Functional Overview 
						

							Basic Printer Functions
This chapter presents a generalized functional overview of the printer and the
printing processes. The following printer systems are discussed:
·DC Controller System/ Power System
·Formatter System
·Image Formation System
·Paper Feed System
·Laser/Scanner System
Figure 5-1 is a generalized block diagram of the printer:
Printer Functional Block Diagram
Figure 5-1
5
Functional
Overview
Functional Overview 5 - 3 
						

							DC Controller/Power System
The DC Controller PCA coordinates all print engine activities, drives the laser, and
coordinates print data from the Formatter PCA with the image formation process.
The DC Controller also includes both AC and DC power supply and distribution
circuitry. The DC Controller controls the following systems and functions:
·Print Engine Control
·Laser and Scanner Drive
·Paper Motion Photosensors (Paper Out, Paper Registration, and Paper Exit
Sensors)
·Motor
·Power System
·AC Power Distribution
·DC Power Distribution
·Overcurrent/Undervoltage Protection
·SleepMode
·High Voltage Power Distribution
Figure 5-2 shows the various DC controller loads.
DC Controller Loads
Low-Voltage
Supply
AC Driver
+5V+12V
Figure 5-2
5 - 4 Functional Overview 
						

							Print Engine Control System
Laser and Scanner Drive
Based on information received from the Formatter, the DC Controller sends signals
to the Laser/Scanner Assembly to modulate the laser diode ON and OFF and to
drive the Laser/Scanner motor. Refer to “Image Formation System,” later in this
chapter for more information.
Paper Motion Monitoring and Control
The DC Controller PCA controls paper motion by continuously monitoring the
various paper sensors and coordinating the timing with the other print processes.
For a detailed explanation of paper movement, and the interaction of photosensors
and solenoid with the paper movement process, refer to the section “Paper Feed
System,” later in this chapter.
+12 V Shutoff Switch
The 12 volt DC power shutoff switch, Switch 101, located on the top of the printer,
is activated by the printer door. The front door must be closed before the printer can
resume printing.
Engine Test Switch
The Test Print, Switch 201, located on the DC Controller, is activated manually
through an access hole at the front of the printer. This switch causes the print engine
to perform a self-test diagnostic which bypasses the Formatter PCA and prints a full
page of black vertical lines. This test is useful for troubleshooting printer problems
because it isolates the print engine from the Formatter PCA. (See Chapter 7,
“Troubleshooting,” to learn more about how to perform an engine test.)
Motor
The Motor is controlled by the DC Controller PCA. The Motor provides all of the
printer’s paper movement.
5
Functional
Overview
Functional Overview 5 - 5 
						

							Power System (on DC Controller PCA)
The AC, DC, and high voltage power supply circuits are all contained within the DC
Controller PCA.
AC Power Distribution
The AC power circuitry supplies AC voltage whenever the power cord is connected
to the AC power source. AC voltage is distributed to the DC power supply circuitry
and to the AC driver circuitry, which controls AC voltage to the fusing assembly’s
heating element.
DC Power Distribution
The DC power distribution circuitry, located on the DC Controller PCA, distributes
+5 V DC and +12 V DC as follows:
+5VDC:Formatter PCA
Photosensors
DC Controller Circuitry
Laser/Beam Detect Circuitry
+12 V DC:Motor
Scanner Motor
Solenoid
+12VA DC:High Voltage Power Supply
Overcurrent/Overvoltage Protection
There are two overvoltage /overcurrent devices in this printer:
·Fuse F101 provides overcurrent protection for the fusing system circuitry. To
check or replace the fuse requires the removal of the DC Controller. Fuse 102
(found only on 110V units) provides overcurrent protection to the printer DC power
supply circuitry.
·In addition, the +12V DC and +5V DC power circuitry contains an overcurrent
protection circuit which automatically shuts off the output voltage when an
overcurrent condition occurs due to a short or abnormal voltage on the load side.
SleepMode
Instead of a power switch, the printer has a SleepMode function. After the printer
has been idle for 15 minutes, it turns itself off by shifting to SleepMode. The front
panel lights remain off, and the printer retains all printer settings and downloaded
fonts and macros while in SleepMode.
5 - 6 Functional Overview 
						

							The printer exits SleepMode and all of the lights power on when any of the
following occur:
·A job is received.
·The Front Panel Button is pressed.
·The printer front door is opened.
NoteThe printer will not enter SleepMode if there is a printer error.
High Voltage Power Distribution
The High Voltage Power Supply PCA applies an overlap of DC and AC voltage to
the primary charging roller and the developing roller. This circuit also applies a
positive or negative DC voltage to the transfer charging roller according to the
instructions from the CPU on the DC Controller PCA.
This circuit also controls the image density by changing the primary AC voltage and
the developing AC bias according to the setting of the print density dial.
High voltage is disabled when the printer’s EP Door is open (i.e., switch SW101 is
open).
5
Functional
Overview
Functional Overview 5 - 7 
						

							Formatter System
The Formatter PCA is responsible for the following:
·Receiving and processing print data from the printer interface.
·Monitoring Front Panel Button and relaying printer status information.
·Developing and coordinating data placement and timing with the print engine.
·Storing font information.
·Communicating with the host computer through the Bi-Directional Interface.
The Formatter PCA receives print data from the Bi-Tronics Interface and converts it
into a dot image. The DC Controller synchronizes the Image Formation System
with the Paper Feed System and signals the Formatter to send the print image data.
The Formatter sends the print image data (dots) in the form of a VIDEO signal and
the printing process begins.
The Formatter PCA also provides mounting locations for additional memory.
CPU
The Formatter PCA incorporates a Motorola 68030 custom-built microprocessor
operating at 24 MHz.
Read Only Memory (ROM)
Besides storing microprocessor control programs, the ROM stores dot patterns of
internal character sets (fonts).
Random Access Memory (RAM)
The RAM stores printing and downloaded font information received from the host
system and temporarily stores a full page of print image data before the data is sent
to the print engine. (See “Page Protect” later in this chapter.) Memory capacity can
be increased by adding a DRAM memory card to the Formatter PCA. Note that
adding memory may also increase print speed when printing complex graphics.
Parallel Interface
The Formatter PCA receives incoming data through its Bi-Tronics interface. The
Bi-Tronics I/O provides high speed and two-way communication between the
printer and the host, allowing the user to change printer settings and monitor printer
status from the host computer. This interface is IEEE-1284 compliant.
5 - 8 Functional Overview 
						

							Control Panel
Status LED Lights
The Formatter uses three LEDs mounted under the printer cover to communicate
printer status to the user. Refer to “Using the Control Panel” in Chapter 3 and
“Printer Error Troubleshooting” in Chapter 7 for more information on the lights.
Front Panel Button
The Formatter PCA is connected to a microswitch located on the control panel
PCA. The single button is used for such functions as self test, reset, and to display
error codes. Refer to “Using the Control Panel” in Chapter 3 for more information
on the Front Panel Button.
Resolution Enhancement (REt)
The Formatter PCA contains circuitry for Resolution Enhancement technology
(REt), which modifies the standard video dot data on its way to the DC Controller
to produce “smoothed” black-to-white boundaries. REt is user-adjustable from
some software applications. Available settings are On or Off.
5
Functional
Overview
Functional Overview 5 - 9