Fuser assembly | HP CP4525DN Laser CC494A#ABA instruction

Fuser assembly

Figure 4-17	Fuser assembly
	1

464 Chapter 4 Parts and diagrams

ENWW

Image 496

HP CP4525DN Laser CC494A#ABA manual Fuser assembly

Contents

Color Laserjet Enterprise CP4020/CP4520 Page HP Color LaserJet Enterprise CP4020- CP4520 Series Printers Copyright and License Trademark Credits Conventions used in this guide Iv Conventions used in this guide Table of contents Removal and replacement Print-quality test 119 Enww Solve problems 265 383 Parts and diagrams Appendix B Product specifications Appendix a Service and supportAppendix C Regulatory information 515 Xvi List of tables 17 Causes and solutions for fuser delivery delay jams 394 Table B-4 Enww List of figures 49Paper-feeder pickup and feed operation 41 Remove the front-top cover 1 100 71 Remove the secondary transfer assembly 1 119 115 Remove the delivery assembly 3 146 161 Remove the tray-pickup drive assembly 1 178 209 Remove the fuser-drive assembly 1 212 19 Test the Tray 1 media-present sensor 261 20 Paper feeder external covers, panels, and doors 470 Xxx Theory of operation Basic operation 1Relationship between the main product systems 1Sequence of operation Sequence of operationPeriod Duration Description Engine-control system 2Engine-control system Solenoids DC controllerComponent abbreviation Component name Switches Clutches Sensors Sensors Motors Abbreviation Name Purpose Failure detection Fans Abbreviation Name Cooling area Type Speed 7High-voltage power supply circuits High-voltage power supplyCircuit Description Biases for each color Low-voltage power supply 8Converted DC voltages Safety Sleep powersave modeLow-voltage power supply failure Overcurrent/overvoltage protection 9Fuser components Fuser controlType of component Abbreviation Name Function Fuser temperature control Fuser sleeve temperature protection Failure detection Fuser unit identification Fuser unit life detection Laser/scanner system 8Laser/scanner system Protective-glass cleaners Laser/scanner failure 9Protective-glass cleaners PGCs Theory of operation Image-formation system ITB 11Image-formation drive system Image-formation process Functional block Steps Description Pre-exposure Primary charging Laser-beam exposure Development Primary transfer Secondary transfer Fusing Separation Drum cleaning ITB cleaningPrint cartridge 23Print-cartridge system Developing-roller engagement and disengagement Intermediate transfer belt ITB unit 25 ITB unit Primary-transfer-roller engagement and disengagement 10Primary-transfer-roller engagement states SL1 27ITB cleaning process Calibration Color-misregistration control Image-stabilization control 11Image-stabilization controls Pickup, feed, and delivery system 29 Paper path Component Abbreviation Component 32Three main units of the pickup, feed, and delivery system Pickup-and-feed unit Cassette pickup Cassette-presence detection Top switch Center switch Bottom switchPaper size 35Cassette lift mechanism Cassette multiple-feed prevention Multipurpose tray pickup 36Multiple-feed prevention Paper feed 37Multipurpose tray pickup mechanism 38Paper-feed mechanism Skew-feed prevention Paper detection Fusing and delivery unit 14Print mode and feed speedSimplex printing Duplex printing Loop control 40Fuser and delivery unit 41Loop-control mechanism Pressure-roller pressurization control 42Pressure-roller pressurization control Duplexing reverse and feed control 43Duplexing unit Duplex print operation Duplex reverse and feed control Enww Jam detection 45Jam detection sensors 16Jams that the product detects Jam Description Optional paper feeder 461 x 500 optional paper feeder 473 x 500-sheet optional paper feeder Motor control 17Electrical components for the paper feederComponent Abbreviation Component name Type Component Drives Failure detection Paper-feeder pickup and feed operation 18Pickup feed components 1 x 500-sheet paper feeder SW2 SW3 SW4 Paper-size detection and cassette-presence detection OFF Paper-feeder cassette lift operation SR2/SR8/SR9 Paper feeder jam detection 51Jam detection 1 x 500-sheet paper feeder 52Jam detection 3 x 500-sheet paper feeder Enww Removal and replacement Removal and replacement strategy Introduction Electrostatic discharge Required tools Before performing service After performing service Post-service test Print-quality test 2Parts removal order 1 Removal and replacement Parts removal order 3Parts removal order 2 Customer self repair CSR components Print cartridges 5Remove the print cartridge 2 7Remove the toner-collection unit 2 Removal and replacement Toner-collection unit 8Remove the toner-collection unit 3 Formatter PCA ESD sensitive component Remove the hard drive Hard driveBefore proceeding, remove the following components 13Remove the hard drive 3 Removal and replacement Memory Dimm Remove the memory Dimm Enable memory Click SettingsClick the Device Settings tab Next to Automatic Configuration , select Update Now Next to Automatic Configuration, select Update Now Installable Options areaClick the Installable Options menu Windows Tray Fuser Feed and separation rollers Trays Pickup roller Tray 24Remove the pickup roller Tray 1 4 Removal and replacement Enww Secondary transfer roller Reinstall the transfer roller 29Reinstall the transfer roller Intermediate transfer belt ITB 32Remove the intermediate transfer belt 3 Enww External panels, covers, and doors Identification and location Upper-left cover 35Remove the upper-left cover 1 Remove one screw 37Remove the upper-left cover 3 Power-supply cover 38Remove the power-supply cover Removal and replacement Left cover Remove the left cover Front-top cover Remove the front-top cover 43Remove the front-top cover 3 Rear-top cover Remove the rear-top cover Right-front cover Remove the right-front cover Reinstall the power button Control-panel assembly Remove the control-panel assembly Enww Front-door assembly Remove the front-door assembly 53Remove the front-door assembly 2 Remove two screws callout 55Remove the front-door assembly 4 Right-rear cover Remove the right-rear cover 58Remove the right-rear cover 2 Rear cover Remove the rear cover Right-door assembly 61Remove the right-door assembly 2 63Remove the right-door assembly 4 Removal and replacement 65Remove the right-door assembly 6 67Remove the right-door assembly 8 Removal and replacement 68Remove the right-door assembly 9 Internal assemblies Cassette feed guide Secondary transfer assembly 72Remove the secondary transfer assembly 2 Reinstall the secondary transfer assembly Separation pad Tray Remove the separation pad Tray 78Remove the separation pad 4 Removal and replacement Enww Registration density RD sensor assembly Remove the RD sensor assembly 84Remove the RD sensor assembly 4 86Remove the RD sensor assembly 6 Removal and replacement Carefully remove the assembly from the product Registration assembly Remove the registration assembly 89Remove the registration assembly 2 91Remove the registration assembly 4 Removal and replacement 93Remove the registration assembly 6 95Remove the registration assembly 8 Removal and replacement Residual-toner-feed motor Remove the residual-toner-feed motor Residual-toner duct and feed assembly Remove the residual-toner duct and feed assembly 99Remove the residual-toner duct and feed assembly 3 Enww Cartridge fan and environmental sensor Remove the cartridge fan and environmental sensor Enww Enww Enww Toner-collection sensor and scanner-thermistor assembly Open the front-door assembly, and then remove one screw Delivery fan Remove the delivery fan 112Remove the delivery fan 2 Removal and replacement Delivery assembly Remove the delivery assembly 115Remove the delivery assembly 3 Removal and replacement Remove two screws 118Remove the delivery assembly 6 Remove the assembly Reinstall the delivery assembly 121Reinstall the delivery assembly 2 123Reinstall the delivery assembly 4 Removal and replacement Duplex-drive assembly Remove the duplex-drive assembly Power-supply fan Remove the power-supply fan Interconnect board ICB Remove the ICB 127Remove the ICB 2 Removal and replacement DC controller PCA only Remove the DC controller PCA only Enww Low-voltage power supply Lvps Remove the low-voltage power supply Enww 134Remove the low-voltage power supply 4 Enww DC controller PCA and tray Remove the DC controller PCA and tray Remove two screws High-voltage power supply lower HVPS-D Remove the high-voltage power supply lower Remove three screws 142Remove the high-voltage power supply lower 3 Release five tabs 146Remove the high-voltage power supply lower 7 Reinstall the high-voltage power supply lower Developing-disengagement motor Remove the developing-disengagement motor Exhaust fan and fan duct Remove the exhaust fan and fan duct Enww Reinstall the exhaust fan and fan duct 152Reinstall the exhaust fan and fan duct Pickup motor Remove the pickup motor Lifter-drive assembly Remove the lifter-drive assembly Enww Lifter base assembly Remove the lifter base assembly Reinstall the lifter base assembly 158Remove the lifter base assembly 2 160Reinstall the lifter base assembly 2 Tray-pickup drive assembly Remove the tray-pickup drive assembly 163Remove the tray-pickup drive assembly 3 Tray-pickup assembly Remove the tray-pickup assembly Enww 168Remove the tray-pickup assembly 5 Removal and replacement Enww 172Remove the tray-pickup assembly 9 Removal and replacement 173Remove the tray-pickup assembly 10 Laser/scanner assembly Y/M Remove the laser/scanner assembly Y/M 176Remove the laser/scanner assembly Y/M 2 Enww 179Remove the laser/scanner assembly Y/M 5 Laser/scanner assembly C/Bk Remove the laser/scanner assembly C/Bk 181Remove the laser/scanner assembly C/Bk 2 Enww 184Remove the laser/scanner assembly C/Bk 5 Reinstall the protective glass cleaner PGC actuators 187Reinstall the PGC actuators 3 Removal and replacement 189Reinstall the PGC actuators 5 High-voltage power supply upper HVPS-T Remove the high-voltage power supply upper 191Remove the high-voltage power supply upper 2 Reinstall the high-voltage power supply upper Yellow, magenta, cyan, and black drum motors Remove the yellow, magenta, cyan, and black drum motors Fuser motor Remove the fuser motor 194Remove the fuser motor ITB motor Remove the ITB motor Main-drive assembly Remove the main-drive assembly 197Remove the main-drive assembly 2 Removal and replacement 198Remove the main-drive assembly 3 Remove 10 screws Enww Reinstall the main-drive assembly 203Reinstall the main-drive assembly 2 Enww Enww Enww Fuser-drive assembly Remove the fuser-drive assembly 212Remove the fuser-drive assembly 4 213Remove the fuser-drive assembly 5 Remove three screws 215Remove the fuser-drive assembly 7 Reinstall the fuser-drive assembly Front door optional paper feeder Enww Rear cover optional paper feeder Right-front cover optional paper feeder 220Remove the right-front cover optional paper feeder Right door optional paper feeder Enww Left cover optional paper feeder Remove the left cover optional paper feeder Enww Right cover optional paper feeder Remove the right cover optional paper feeder Rear-right cover optional paper feeder Remove the rear-right cover optional paper feeder Pickup assembly optional paper feeder Remove the pickup assembly optional paper feeder 231Remove the pickup assembly optional paper feeder 3 Enww Lifter assembly optional paper feeder Remove the lifter assembly optional paper feeder Lifter-drive assembly optional paper feeder Remove the lifter-drive assembly optional paper feeder Pickup motor assembly optional paper feeder Remove the pickup motor optional paper feeder assembly Controller PCA optional paper feeder Remove the controller PCA optional paper feeder Solve problems Solve problems checklist Solve problems checklist Menu map Print a menu map Troubleshooting process Determine the problem sourcePre-troubleshooting checklist 1Pre-troubleshooting checklist Calibrate the product on Troubleshooting flowchart 2Troubleshooting flowchartPower on Event log Information pages Image quality Interface Power subsystem Power-on checksPower-on troubleshooting overview Power-on timing approximate Enww Tools for troubleshooting Individual component diagnosticsLED diagnostics Understand lights on the formatter Heartbeat LED Engine diagnosticsDefeating interlocks Disable cartridge check Engine-test button Paper-path test 3Engine-test button 3Manual sensor diagnostic tests Default state of bitsSensor or switch name Sensor or switch number Manual sensor test special-mode test TOP top of page sensor C loop sensors Fuser delivery sensor Duplex re-pickup sensor Output bin full sensor Developer alienation Fuser pressure-release sensor Primary transfer-roller-disengagement sensor Enww Media sensor 16 Media sensor Front-door switch Right-door switch 5Manual sensor test 2 diagnostic tests Manual sensor test 2 special-mode test Test each switch individually Solve problems Tray 1 paper present sensor Tray 2 paper present sensor Tray 2 paper surface 1 and 2 sensors Tray 2 paper size switches Tray 3 paper size switches Tray 3 paper present sensorTray 3 feed sensor Tray 3 paper surface 1 and 2 sensors Tray 4 paper size switches Tray 5 paper size switchesTray 5 paper present sensor Tray 5 feed sensor Enww Defeating Enww Enww New ITB sensor 25Test the new ITB sensor Tray 3, 4, and 5 right door switch 26Test the right door switch Solve problems 7Paper-path sensors diagnostic tests Paper-path sensors testPrint/stop test Sensor name Sensor number Component test special-mode test Component tests8Component test details Yellow Laser Scanner Fuser MotorFuser Pressure Release Motor Alienation Motor Duplex Refeed Clutch Solenoid Repeat Diagrams Block diagrams 28Optional paper feeder 1 x 500-sheet 29Optional paper feeder 3 x 500-sheet Plug/jack locations 9Formatter PCA Location of connectors DC controller connector locations 10DC controller connectors 32Controller PCA connectors 11Controller PCA connectors Locations of major components 33External component locations 34Major component locations 1 35Major component locations 2 36Major component locations 3 11 9 Ite Description 38PCA component locations 39Optional paper feeder 1 x 500-sheet component locations 1 40Optional paper feeder 1 x 500-sheet component locations 2 41Optional paper feeder 3 x 500-sheet component locations 1 42Optional paper feeder 3 x 500-sheet component locations 2 General timing chart Timing chart Circuit diagrams General circuit diagram 1 Control Paper feeder circuit diagram 1 X 500-sheet Paper feeder circuit diagram 3 X 500-sheet Open the HP Easy Printer Care software HP Easy Printer CareHP Easy Printer Care software sections Settings tab Section Options Support tabHP Proactive Support Overview and Support tabs Section Options Alert Settings link Color Access Control Print-quality-troubleshooting pages Internal print-quality test pages Yellow Green 51Black print-quality troubleshooting Diagnostics Diagnostics Cleaning Create and use the cleaning Configuration Configuration Memory Event log Security Paper trays and options Security Settings information HP embedded Jetdirect Embedded protocol 54 Embedded protocol 12Important information on the configuration pages Finding important information on the configuration pagesColor-band test Print-quality troubleshooting tools Repetitive defects ruler Calibrate the product Control panel menus Control panel menusShow Me How menu Retrieve job menu Enww When Print or Print and Delete is ALL Jobs no PIN PrintHold jobs, Print and Delete is Delete Information menu Paper handling menu Manage supplies menu Color Cartridges Stop ContinuePrint in Black Transfer KIT Stop User Defined LOW Yellow Cartridge Magenta CartridgeCyan Cartridge Black Cartridge Transfer KIT Configure device menu Printing menu Default Paper Size Default Custom Paper Unit of MeasureSize Dimension Print PS Errors OFF PCL sub-menu Print Quality menu Mode Expanded X1 ShiftY1 Shift X2 Shift Adjust Paper Print ModeRestore Optimize NOW Delay Auto Cleaning OFF CleaningAuto Cleaning Letter Edge Control OFF Create Select the Create CleaningProcess System setup menu PS Defer Media Enabled DisabledUSE Requested Tray Exclusively First USE Another Tray Enabled Letterhead Mode OFFSleep Delay Minute Alternative Wake Time CustomOptimum SPEED/ENERGY Faster First Usage Save Energy JAM Recovery Auto Auto Continue OFFRAM Disk Auto Language Menu 13Embedded Jetdirect menu IPV4 Settings Config Method Bootp Settings Subnet MaskDefault Default IP Auto IP IPV6 Settings Enable SettingsDhcp Renew Primary DNS Idle Timeout IPX/SPX EnableAppletalk Enable OFF DLC/LLC Enable Disable ResetReset Security YES Diagnostics Embedded Tests Snmp Test YES Data Path Test YESSelect ALL YES Tests Print Results YES Ping ResultsPackets Sent Packets Refresh YES Link Speed Auto 10T Half 10T Full 100TX Half 100TX Full Resets menu Diagnostics menu Paper Path Sensors Paper Path TestSource ALL Trays Tray Service menu Product PINsVoltage power supply Color Band Test Print Test Interpret control-panel messages Control-panel message typesControl-panel messages XX values 13.XX.YY Fuser Area JAM 13.XX.YY Fuser Wrap JAM13.XX.YY JAM Above TOP Output BIN 13.XX.YY JAM in Lower Right Door Transfer Unit Error Embedded I/O Buffer OverflowParallel I/O Buffer Overflow Parallel Serial Buffer Fuser Error Xxxx ErrorTo continue turn off then on See Fuser on XX Error XY Error55.XX.YY DC Controller Error Error See DC controller PCA and tray Description Recommended action Error 59.A0 Error BO Cleaning Motor Error59.C0 Error Replace Toner Collection Unit 59.F0 Error No System ValuesPermanent Storage Full Storage Error Settings 8X.YYYY EIO Error8X.YYYY Embedded Jetdirect Error Changed Calibration Reset Pending Black Cartridge LOWBlack Cartridge LOW Less than Xxxx Pages Black Cartridge Very LOW Cleaning Disk X% Complete Card Slot Device FailureCard Slot File Operation Failed Card Slot File System is Full Cleaning Cyan Cartridge LOW Close Lower Right DoorClose Right Door Collection Unit Almost Full Cyan Cartridge Very LOW Data ReceivedDATE/TIME = YYYY/MMMM/DD Hhmm EIO X Disk Initializing HP Secure Drive Disabled EIO is Write ProtectedEIO not Initialized Expected Drive Missing Install Color Cartridge Install FuserInstall Supplies Install Transfer Unit Media insert required in tray Loading Program Magenta Cartridge LOWMagenta Cartridge LOW Less than Xxxx Pages Magenta Cartridge Very LOW NON HP Supply Installed Moving SolenoidMoving Solenoid and Motor Printing Stopped RAM Disk Device Failure RAM Disk File Operation FailedRAM Disk File System is Full RAM Disk is Write Protected Replace Supplies Using black only Remove Shipping SheetReplace Color Cartridge Replace Fuser KIT Replace Transfer KIT ROM Disk Device Failure ROM Disk File Operation Failed ROM Disk File System is FullROM Disk is Write Protected Sanitizing Disk X% Complete Supplies LOW Manage Supplies menu onPrinting Black only Supplies Very LOW Toner Collection Unit LOW Toner Collection Unit Very LOWTransfer KIT LOW Transfer KIT LOW Less than Xxxx Pages Tray X Type Size Tray X Empty Type SizeTray X Open Tray X Overfilled Unsupported Drive Installed Unsupported Supply InstalledUSB Accessory Error USB Accessory not Functional Wait for Printer to Reinitialize Waiting for Tray X to LiftWarming UP Yellow Cartridge LOW Yellow Cartridge Very LOW Yellow Cartridge Very LOW To continue press OK Print an event log Event log messagesShow an event log Sample event log Clear the event log Event log message table Event log message Description Comments Configure DEVICE, and then Quick Calibrate NOW, Then press theOK button DC controller Nvrm is not Reading the header number and size 99.00.08 Common causes of jams Clear paper jamsProduct is jammed ITB 15Common causes of jams by area Jam code Type of jam Procedure Jam locations Clear jams in the right door 13.XX.YY JAM in Optional Trays Enww Enww Clear jams in the output bin area Clear jams in Tray Enww Clear jams in Tray 2 or optional Trays 3, 4, or Clear jams in the lower right door Tray 3, 4, or Jams in the output bin Jam causes and solutionsJams in the fuser and transfer area 19Causes and solutions for fuser delivery stationary jams 20Causes and solutions for residual media jams 21Causes and solutions for pickup delay jams 23Causes and solutions for duplexing reverse jams 22Causes and solutions for pickup stationary jams24Causes and solutions for duplex repick jams 25Causes and solutions for residual media jams Right-door assembly on 26Causes and solutions for pickup delay jam 1 tray pickup Jams in Tray 1, Tray 2 and internal paper path 27Causes and solutions for pickup stationary jams Jams in Tray 3, 4, 29Causes and solutions for residual media jams Change jam recovery Set the jam recovery feature Solve paper-handling problems Product feeds multiple sheetsProduct feeds incorrect page size Product pulls from incorrect tray Paper does not feed automatically Paper does not feed from Tray 2, 3, 4, orPaper does not feed automatically Paper does not feed from Tray 2, 3, 4, or Transparencies or glossy paper will not feed Envelopes jam or will not feed in the productTransparencies or glossy paper will not feed Envelopes jam or will not feed in the product Product will not duplex or duplexes incorrectly Output is curled or wrinkledOutput is curled or wrinkled Automatic Configuration list Under Installable Options, click Update NowProperties or Printing Preferences PRE-ROTATION Mode 30MP modes under the Adjust Paper Types sub menuUse manual print modes 31MP modes under the Optimize submenu Problem Sample Cause Solution Solve image-quality problemsImage defects table Transfer belt ITB on Assembly Y/M on page 186 or Power supply lower HVPS-D Assembly. See Secondary transfer Execute a Pressure roller clean Clean the paper path Clean the productClean the product Solve performance problems Problem Cause Solution Solve direct-connect problems Solve connectivity problemsSolve network problems Solve connectivity problems Service mode functions Service menu Refurbish Cycle Count Refurbish page CountSerial Number Service ID Cold Reset PaperNEW Registration Roller Media Sensor Value Product resets Restore factory-set defaultsHard disk initialization optional Nvram initialization Product updates Product cold reset Parts and diagrams Order parts, accessories, and supplies Accessories Part numbersPrint cartridges and toner collection unit Memory 1Maintenance kits Service maintenance kitsCustomer self repair CSR parts 2110V and 220V unique components Unique components3Simplex and duplex unique components Screws 4Common fasteners How to use the parts lists and diagrams External covers, panels, and doors 1External covers, panels, and doors 5External covers, panels, and doors Description Part number Qty Right door assembly 2Right door assembly 6Right door assembly Front door assembly 7Front door assembly Internal components Internal components 1 8Internal components 1 Internal components 2 9Internal components 2 Internal components 3 6Internal components 3 10Internal components 3 Internal components 4 11Internal components 4 Internal components 5 8Internal components 5 12Internal components 5 Internal components 6 Simplex Model Duplex Model 13Internal components 6 Internal components 7 10Internal components 7 14Internal components 7 Cassettes Cassettes 15 Cassette Paper pickup assembly 16Paper pickup assembly Tray 1 paper pickup assembly 13Tray 1 paper pickup assembly 17Tray 1 paper pickup assembly Simplex Model Duplex Model 18Registration assembly 15Secondary transfer assembly 19Secondary Transfer assembly 16Delivery assembly 20Delivery assembly Fuser assembly Fuser assembly 21Fuser assembly PCAs 18 PCAs 22 PCAs Paper feeders AssessoriesPaper feeders 23Paper feeders Paper feeder external covers, panels, and doors 1x500 3x500 24Paper feeder external covers, panels, and doors 500 paper feeder main body 500 paper feeder main body 251 X 500 paper feeder main body 223 X 500 paper feeder main body 263 X 500 paper feeder main body Alphabetical parts list 27Alphabetical parts list Alphabetical parts list Delivery assembly Fuser drive assembly, simplex RM1-6702-000CN Paper pickup assembly Tray 1 paper pickup assembly Shutter arm assembly RM1-5585-000CN Upper main cable assembly RM1-5800-000CN Numerical parts list 28Numerical parts list RC2-4218-000CN Tray, waste toner catch Enww RK2-2604-000CN Flat flexible cable DCC to Hvps lower RM1-5520-000CN Cover, inner RM1-5781-000CN High voltage power supply, upper Enww WC2-5637-000CN Switch, push Enww Service and support Hewlett-Packard limited warranty statement Page HP Color LaserJet Fuser Kit Limited Warranty Statement End User License Agreement Transfer Enww Customer self-repair warranty service Customer support Product specifications Physical specifications Performance specificationsElectrical specifications Table B-1Product dimensions Acoustic specifications Environmental specificationsTable B-3Power requirements Table B-4Power consumption average, in watts1246 Skew specifications Table B-6Media registration and image placement accuracy Regulatory information FCC regulations Environmental product stewardship program Return and recycling instructions PaperUnited States and Puerto Rico Non-U.S. returns Chemical substances Material restrictionsHP Color LaserJet Enterprise CP4020-CP4520 Series Material Safety Data Sheet Msds For more information Declaration of Conformity Safety statements Laser safetyVcci statement Japan Power cord instructions Power cord statement Japan Varoitus GS statement Germany Symbols/Numerics Cabinet/stand Dhcp See also jams Nvram See also counts Enww Recycling Enww See also cassette Enww Page CC489-90936* *CC489-90936