Troubleshooting Manual & Repair Manual & Parts List HP LaserJet PRO MFP M521;
This service manual, is the full HP LaserJet PRO MFP M521 Service Repair Manual.
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To see what contain, please read table of contents:

Content for TROUBLESHOOTING MANUAL:
1. THEORY OF OPERATION
Basic operation
Major systems
Product block diagram
Sequence of operation
Normal sequence of operation
Formatter-control system
Auto on/Auto off mode
Input/output
CPU
Memory
Firmware
Nonvolatile memory
Control panel
Engine-control system
Motors, fans, clutches, solenoids, switches, and sensors
DC controller operations
Fuser-control circuit
Fuser failure detection
Fuser temperature control
Fuser protective function
Low-voltage power supply
Overcurrent/overvoltage protection
High-voltage power supply
Laser/scanner system
Laser failure detection
Image-formation system
Electrophotographic process
Image formation process
Latent-image formation stage
Primary charging
Laser beam exposure
Developing stage
Toner cartridge
Transfer stage
Fusing stage
Cleaning stage
Toner detection
Pickup, feed, and delivery system
Paper trays
Photo sensors and switches
Solenoids and clutches
Tray 1 or Tray 2
Pickup and feed unit
Cassette paper size detection/cassette paper detection
Cassette pickup
Tray 1 paper pickup
Paper pickup and feed
Jam detection
Additional tray
Tray driver PCA
Paper pickup and feed
Paper level and size detection
Jam detection
Scanner system
Scanner power-on sequence of events
Copy or scan sequence of events

2. SOLVE PROBLEMS
Solve problems checklist
Menu map
Troubleshooting process
Pre-troubleshooting checklist
Determine the problem source
Troubleshooting flowchart
Power subsystem
Power-on checks
Power-on troubleshooting overview
Control-panel checks
Tools for troubleshooting
Diagrams
Block diagrams
Location of connectors
DC controller connections
Formatter connections
Plug and port locations
Locations of major assemblies
General timing charts
Circuit diagrams
Use HP Device Toolbox (Windows)
Internal print-quality test pages
Clean the paper path
Print the configuration page
Print quality troubleshooting tools
Repetitive defects ruler
Control-panel menus
Setup Menu
HP Web Services
Reports menu
Self Diagnostics menu
Fax Setup menu
System Setup menu
Service menu
Network Setup menu
Quick Forms menu
Function specific menus
USB Flash Drive
Fax Menu
Copy Menu
Scan Menu
Apps
Interpret control-panel messages
Control panel message types
Control panel messages
49 Error, Turn off then on
50.x Fuser Error
51.XX Error
54.XX Error
55.X Error
57 Fan Error, Turn off then on
59.X Error
79 Error Turn off then on
Black Cartridge low
Black Cartridge very low
Cleaning
Communication Error
Device error, press OK
Document feeder door is open. Canceled fax
Door open
Fax is busy. Canceled send
Fax is busy. Redial pending
Fax receive error
Fax Send error
Fax storage is full. Canceling the fax receive
Fax storage is full. Canceling the fax receive
Fax storage is full. Canceling the fax send
Genuine HP supply installed
Incompatible
Install cartridge
Invalid driver Press OK
Jam in Tray 1, Clear jam and then press OK
Load tray 1 Press OK for available media
Load Tray 1 , Press OK to use available media
Load Tray 1, / Cleaning mode, OK to start
Load Tray : [Type], [Size]
Manual Duplex Load Tray 1, Press OK
Manual feed , Press OK to use available media
Memory is low. Press OK
Misprint, Press OK
No dial tone
No fax answer. Canceled send
No fax answer. Redial pending
No Fax Detected
Print failure, press OK. If error repeats, turn off then on
Remove shipping lock from cartridge
Replace
Unexpected size in tray 1 Load Press OK
Unsupported Press OK to continue
Used cartridge is installed Press OK to continue
Event-log messages
Print the event log
Show an event log
Event log messages
Clear jams
Jam locations
Clear jams in the document feeder
Clear jams in the output area
Clear jams in Tray 1
Clear jams in Tray 2 or optional Tray 3
Clear jams in the fuser
Clear jams in the duplexer
Paper feeds incorrectly or becomes jammed
The product does not pick up paper
The product picks up multiple sheets of paper
The document feeder jams, skews, or picks up multiple sheets of paper
Prevent paper jams from the paper trays
Solve image-quality problems
Image defect examples
Clean the product
Clean the pickup and separation rollers
Clean the paper path
Clean the scanner glass strip and platen
Clean the document feeder pickup rollers and separation pad
Clean the touchscreen
Solve performance problems
Solve connectivity problems
Solve USB connection problems
Solve wired network problems
Poor physical connection
The computer is using the incorrect IP address for the product
The computer is unable to communicate with the product
The product is using incorrect link and duplex settings for the network
New software programs might be causing compatibility problems
The computer or workstation might be set up incorrectly
The product is disabled, or other network settings are incorrect
Solve wireless network problems
Wireless connectivity checklist
The product does not print after the wireless configuration completes
The product does not print, and the computer has a third-party firewall installed
The wireless connection does not work after moving the wireless router or product
Cannot connect more computers to the wireless product
The wireless product loses communication when connected to a VPN
The network does not appear in the wireless networks list
The wireless network is not functioning
Perform a wireless network diagnostic test
Reduce interference on a wireless network
Service mode functions
Service menu
Service menu settings
Restore the factory-set defaults
Secondary service menu
Open the secondary service menu
Secondary service menu structure
Product resets
NVRAM initialization
Super NVRAM initialization
Solve fax problems
Checklist for solving fax problems
Perform a fax diagnostic test
Fax trace report
Fax error report printing
Print all fax reports
Print individual fax reports
Set the fax error report
Set the fax-error-correction mode
Change the fax speed
Solve problems sending faxes
An error message displays on the control panel
The Communication Error message appears
No dial tone
The Fax is busy. message appears
The No fax answer. message appears
Document feeder paper jam
The Fax storage is full. message appears
Scanner error
The control panel displays a Ready message with no attempt to send the fax
The control panel displays the message "Storing page 1" and does not
progress beyond that message
Faxes can be received, but not sent
Product is password protected
Unable to use fax functions from the control panel
Unable to use speed dials
Unable to use group dials
Receive a recorded error message from the telephone company when trying to send a fax
Unable to send a fax when a telephone is connected to the product
Solve problems receiving faxes
The fax does not respond
The fax has a dedicated telephone line
An answering machine is connected to the product
The Answer Mode setting is set to the Manual setting
Voice mail is available on the fax line
The product is connected to a DSL telephone service
The product uses a fax over IP or VoIP telephone service
An error message displays on the control panel
The No Fax Detected message displays
The Communication Error message appears
The Fax storage is full. message appears
The Fax is busy. message appears
A fax is received but does not print
The Private Receive feature is on
Sender receives a busy signal
A handset is connected to the product
A telephone line splitter is being used
No dial tone
Cannot send or receive a fax on a PBX line
Solve general fax problems
Faxes are sending slowly
Fax quality is poor
Fax cuts off or prints on two pages
Product updates
Manually update the firmware
Set the product to automatically update the firmware
Appendix A Service and support
Hewlett-Packard limited warranty statement
HP's Premium Protection Warranty: LaserJet toner cartridge limited warranty statement
HP policy on non-HP supplies
HP anticounterfeit Web site
Data stored on the toner cartridge
End User License Agreement
OpenSSL
Customer self-repair warranty service
Customer support

Appendix B Product specifications
Physical specifications
Power consumption, electrical specifications, and acoustic emissions
Environmental specifications

Appendix C Regulatory information
FCC regulations
Environmental product stewardship program
Protecting the environment
Ozone production
Power consumption
Toner consumption
Paper use
Plastics
HP LaserJet print supplies
Return and recycling instructions
United States and Puerto Rico
Multiple returns (more than one cartridge)
Single returns
Shipping
Non-U.S. returns
Paper
Material restrictions
Disposal of waste equipment by users
Electronic hardware recycling
Chemical substances
Material Safety Data Sheet (MSDS)
For more information
Declaration of conformity (dn model)
Declaration of conformity (dw model)
Safety statements
Laser safety
Canadian DOC regulations
VCCI statement (Japan)
Power cord instructions
Power cord statement (Japan)
EMC statement (China)
EMC statement (Korea)
EMI statement (Taiwan)
Laser statement for Finland
GS statement (Germany)
Substances Table (China)
Restriction on Hazardous Substances statement (Turkey)
Restriction on Hazardous Substances statement (Ukraine)
Additional statements for telecom (fax) products
EU Statement for Telecom Operation
New Zealand Telecom Statements
Additional FCC statement for telecom products (US)
Telephone Consumer Protection Act (US)
Industry Canada CS-03 requirements
Vietnam Telecom wired/wireless marking for ICTQC Type approved products
Additional statements for wireless products
FCC compliance statement-United States
Australia statement
Brazil ANATEL statement
Canadian statements
Products with 5 GHz Operation Industry of Canada
Exposure to Radio Frequency Radiation (Canada)
European Union regulatory notice
Notice for use in France
Notice for use in Russia
Mexico statement
Taiwan statement
Korean statement
Vietnam Telecom wired/wireless marking for ICTQC Type approved products
INDEX

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Content for REPAIR MANUAL & PARTS LIST:
1. REMOVAL AND REPLACEMENT
Removal and replacement strategy
General cautions during removal and replacement
Electrostatic discharge
Required tools
Types of screws
Service approach
Before performing service
After performing service
Post-service test
Print-quality test
Location of connectors
DC controller connections
Formatter connections
Parts removal order
Removal and replacement procedures
Customer self repair (CSR) assemblies
Toner cartridge
Tray 2 or Tray 3 assembly
Document feeder rollers
Document feeder pickup roller
Document feeder separation roller
Document feeder separation pad
External panels, covers, doors, and formatter
Formatter cover
Formatter PCA
Fax PCA and cable
Interconnect board (ICB)
Formatter stay
Dummy cover
Rear cover assembly
Left cover
ENWW v
Right-rear cover
Tray 1 cover
Cartridge-door assembly
Right cover assembly
Lower right cover
Reinstall the lower right cover
I/O plate
Document feeder assemblies and scanner
Document feeder/scanner assembly
Document feeder whole unit kit and scanner whole unit kit
Document feeder hinge assembly
Control-panel top-cover
Control-panel assembly
USB PCA
Control-panel FFC
USB cable and USB grounding cable
Wi-Fi module and cable
Main assemblies
Tray 1 pickup roller
Tray 1 separation pad
Tray 2 or Tray 3 pickup roller
Tray 2 or Tray 3 separation pad
Tray 2 or Tray 3 base-plate roller assembly
Transfer roller
Fuser
Duplex paper-feed assembly
Registration roller assembly
Power-switch assembly
Interlock-switch assembly
Tray sensor PCA
Main fan
Top cover
Laser scanner
Tag holder assembly
DC controller
Low-voltage power supply (LVPS)
Tray 2 paper pickup assembly
Tray 1 or Tray 2 pickup solenoid
Fuser motor
Pendulum assembly
Sub fan and fan duct
Environmental sensor
High-voltage power supply (HVPS)

2. PARTS AND DIAGRAMS
Order parts by authorized service providers
Order parts, accessories, and supplies
Supplies part numbers
Customer self-repair (CSR) and service kits
Related documentation and software
Fasteners used in this product
How to use the parts lists and diagrams
Assembly locations
Base product (no optional trays or accessories)
Base product (optional trays or accessories)
Covers
Document feeder and scanner assemblies
Control-panel and USB PCA assemblies
Document feeder assemblies
Internal assemblies (1 of 6)
Internal assemblies (2 of 6)
Internal assemblies (3 of 6)
Internal assemblies (4 of 6)
Internal assemblies (5 of 6)
Internal assemblies (6 of 6)
Input devices
500-sheet input tray (Tray 3)
Alphabetical parts list
Numerical parts list
INDEX

Number of pages: 414.