HP 2500 L Service Manual

EN 4 Theory of operation59
4Theory of operation
Chapter contents
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  60
Engine control system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  61
Basic sequence of operation  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  62
Power-on sequence  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  63
Motors...

60Theory of operation C9706-90926
Introduction
This chapter presents an overview of the relationships between major components in the HP 
Color LaserJet 2500 series printer, and includes a detailed discussion of the image-formation 
system. The following systems are discussed:

engine control system

laser/scanner system

pickup and feed system

image-formation system
Figure 10. Cross-section of the printer
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1 Laser/scanner 9 Transfer belt cleaning roller...

EN 4 Theory of operation61
Engine control system 
The engine control system coordinates all printer functions. It drives the laser/scanner system, 
the image formation system, and the pickup and feed system. 
The engine control system contains the following components:

dc controller

high-voltage power-supply PCB

low-voltage power unit:
fuser-control circuit
 low-voltage power-supply PCB
Figure 11. Engine control system (includes the basic configuration of the printer) 

62Theory of operation C9706-90926
Basic sequence of operation
Operation sequences are controlled by the CPU in the dc controller in the engine control system. 
Table describes engine operations for each period of a print operation.
Table 15. Basic sequence of operation
Period Duration Purpose Remarks
WAIT
(wait) From the time the power 
switch is turned on until 
transfer-belt cleaning is 
complete.  Clears potential from the 
drum surface and cleans the 
transfer belt.
See figure 12 for a complete...

EN 4 Theory of operation63
Power-on sequence
The power-on sequence is represented by the flowchart in figure 12.
Figure 12. Power-on sequence 

64Theory of operation C9706-90926
Motors and fans
Figure 13.Motors and fans
1
23
4
5
6
Table 16. Motors and fans
Reference Description
1 Engaging motor
2 Developing-rotary motor
3 Toner-cartridge motor
4 Fuser motor
5 Main motor
6 Cooling fan 

EN 4 Theory of operation65
Laser/scanner system
The laser/scanner system receives video signals from the dc controller, and then it converts the 
signals into latent images on the photosensitive drum. The dc controller controls the laser/
scanner.
Figure 14. Laser/scanner system 

66Theory of operation C9706-90926
Pickup and feed system
The pickup and feed system consists of several types of feed rollers and sensors. The dc 
controller drives the paper and feed system by controlling two motors, two clutches, and the 
solenoid.
Two photo-interrupters (PS1 and PS711) detect media as it passes. If media does not reach or 
pass each sensor within the specified time period, the dc controller determines that a jam has 
occurred and alerts the video controller circuit.
The following...

EN 4 Theory of operation67
Paper trays 
The dc controller drives the operation sequence of the paper trays. It signals the driver PCB in 
tray 2 (250-sheet paper tray) and in tray 3 (250-sheet paper tray), and then each driver PCB 
controls the motors and solenoids in its paper tray.
The following components are identified in figure 16:

DCM701 gear-train motor (printer)

SL9 pickup solenoid (optional tray 2)

PS716  paper sensor (optional tray 2)

PS717 paper-feed sensor
Note Only tray 2 (250-sheet...

68Theory of operation C9706-90926
Jam detection 
The registration sensor (PS711) and the fusing paper sensor (PS1) detect media moving 
through the printer. If a jam is detected, the dc controller immediately stops the printing process 
and sends a message to the video controller circuit. 
A jam can be detected under any of the following conditions:

Pickup delay jam. The leading edge of the paper does not reach the registration sensor 
(PS711) within 1.1 seconds (tray 1), 1.7 seconds (optional tray 2),...