HP Laserjet 4 Manual

Printing from the MP Tray (Tray 1) 
MP tray selection is provided by the Formatter PCA, as
configured by the operator’s control panel or by a software
application. The MP tray (Tray 1) feed system’s paper motion
begins when the DC Controller PCA, after receiving a 
PRNT
signal, starts the Scanner Motor (M5) and the Main Motor (M1).
When the fusing roller reaches the minimum operating
temperature (183° C), the MP pickup roller clutch solenoid (SL2)
is energized for 1 second, allowing the MP pickup roller...

Printing from the PC Tray (Tray 2)  
PC tray selection is provided by the Formatter PCA, as
configured by the control panel or by software. When the DC
Controller PCA receives a 
PRNT signal, it starts the Scanner
Motor (M5) and the Main Motor (M1). When the fusing roller
reaches the minimum operating temperature (approximately 183°
C), the PC tray (Tray 2) pickup roller clutch solenoid (SL1) is
energized for 1 second, allowing the roller to make one rotation.
The PC tray pickup roller then feeds a sheet...

Po w e r  S y s t e m  
When the main power switch is turned ON, the AC Power Supply
provides AC voltage to the DC Power Supply and the fuser
assembly heat lamp. The paper path doors must be closed to
activate the AC power supply door switches before voltage is
provided to the heat lamp.  
The DC Power Supply generates +5V DC, and +24V DC for use
by the Formatter PCA and the DC Controller PCA. The DC
Controller PCA distributes voltages to the remaining electrical
assemblies. Over-current protection for...

Figure 5-20 Power System Block Diagram
5-32 Functional Overview 

Basic Sequence of Operation  
The Formatter PCA and the DC Controller PCA share
information during printer operation. Connector J7 on the
formatter and connector J207 on the DC controller form a link
which operates as a serial data bus. This allows printer status,
command information, and dot-image data to be passed between
both controllers.
Standard Printer Operation  
The following events take place during normal printer operation:
1After the printer’s power is turned ON, the printer enters the
Warmup...

6Each time the formatter receives a synchronized BD signal
from the DC controller, the formatter sends a VIDEO data
stream (
VDO) to the DC controller.
7After the DC controller receives the VDO data, the DC
controller translates it into a VIDEO OUT signal (
VDOUT)
that switches the laser diode ON and OFF.
8The laser beam, created by the laser diode, reflects off the
scanner mirror onto the photosensitive drum to form a latent
electrostatic image, writing a single line of print (dot) data.
9After the last...

This a 2 panel pull-out.
Figure 5-21 MP Tray Timing Diagram—HP LaserJet 4/4M
Functional Overview  5-35 

This a 2 panel pull-out.
Figure 5-22 MP  (Tray 1) Timing Diagram—HP LaserJet 4
Plus/4M Plus/5/5M/5N
5-36 Functional Overview 

Warmup Period  
The Warmup period begins when the printer’s power is turned
ON, and ends when the fusing roller temperature reaches 172° C.
When the printer is switched ON, the exhaust fan (FM1) begins
low-speed rotation and the fusing roller maintains 172° C. The
DC controller then switches the main motor (M1) ON, and applies
AC high voltage to the primary charging roller to remove any
residual charge from the photosensitive drum.  Negative high
voltage is applied to the transfer roller to clean toner...

Initial Rotation Period  
When the DC controller receives a PRINT signal (PRNT) from the
formatter, the DC controller allows the fusing roller to begin
warming up to approximately 183° C, and starts the main motor
(M1), the pickup motor (M2), and scanner motor (M5). Next, the
laser diode turns ON and generates a sweep beam used to adjust
the laser power (APCIN). After the DC controller receives a
BEAM DETECT signal (
BD) initiated by the sweep beam, the
laser power stabilizes and the sweep beam turns...