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Dell U2421HE Service Manual
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Product Announcement:
This product is certificated to meet RoHS
Directive and Lead-Free produced definition.
Using approved critical components only is
recommended when the situation to replace
defective parts. Vender assumes no liability
express or implied, arising out of any unauthorized
modification of design or replacing non-RoHS
parts. Service providers assume all liability.
Qualified Repairability:
Proper service and repair is important to the safe,
reliable operation of all series products. The
service providers recommended by vender should
be aware of notices listed in this service manual in
order to minimize the risk of personal injury when
perform service procedures. Furthermore, the
possible existed improper repairing method may
damage equipment or products. It is recommended
that service engineers should have repairing
knowledge, experience, as well as appropriate
product training per new model before performing
the service procedures.
NOTICE:
! To avoid electrical shocks, the products should be
connected to an authorized power cord, and turn
off the master power switch each time before
removing the AC power cord.
! To prevent the product away from water or
expose in extremely high humility environment.
! To ensure the continued reliability of this
product, use only original manufacturer's
specified parts.
! To ensure following safety repairing behavior, put
the replaced part on the components side of
PWBA, not solder side.
1. Important Safety Notice
! To ensure using a proper screwdriver, follow the
! Using Lead-Free solder to well mounted the
! The fusion point of Lead-Free solder requested in
torque and force listed in assembly and
disassembly procedures to unscrew screws.
parts.
the degree of 220°C.

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Summary of Contents for Dell U2421HE

  • Page 1 1. Important Safety Notice Product Announcement: ! To ensure using a proper screwdriver, follow the This product is certificated to meet RoHS torque and force listed in assembly and Directive and Lead-Free produced definition. disassembly procedures to unscrew screws. Using approved critical components only is ! Using Lead-Free solder to well mounted the recommended when the situation to replace parts.
  • Page 2 2. Exploded view diagram with list of items...
  • Page 3 3. Wiring Connectivity Diagram LED DRIVER Panel FK board Interface board USB board HDMI1 Audio out USB1 USB2 USB3...
  • Page 4 4. Disassembly and Assembly Procedures Lift the rear cover up carefully. Disconnect the USB Necessary repair and test equipment: 1. Philips-head screwdriver FFC cable from the connector of the interface board, and then remove the rear cover. 4.1 Disassembly Procedures: Remove the monitor stand base: 1.
  • Page 5 4. Disassembly and Assembly Procedures Use a Philips-head screwdriver to remove 5pcs screws for unlocking the front bezel with the assembled unit. (No.1~5 screw size=M2x2.7, Torque=3±0.5kgfxcm) se a Philips-head screwdriver to remove 2pcs screws(left and right) for unlocking the front bezel Tear off 2pcs acetate tapes for releasing the panel with the panel module, then disassemble the front lamp cables, then unplug the panel lamp cables from...
  • Page 6 4. Disassembly and Assembly Procedures Turn over the bracket chassis module. Remove the Mylar from the hooks of the bracket, and then use a Philips-head screwdriver to remove screws for unlocking AC power outlet. (No.1~2 screw size=M3x10, Torque=6 kgfxcm) ±0.5 Use a Philips-head screwdriver to remove 7pcs screws...
  • Page 7 4. Disassembly and Assembly Procedures 4.2 Assembly Procedures: Take 1pcs driver board, connect the correct cables of the power board to the connector of the driver board, Place a bracket chassis base on a protective then turn over the driver board and locate it into the cushion, then stick 6pcs Silicon sheets on the bracket.
  • Page 8 4. Disassembly and Assembly Procedures Panel preparation: Take out 1pcs panel module from Connect the panel power cables to the two the carton, remove the protective film by tearing off connectors of the panel module, then fix the cables the tapes, then Examine the panel surface with 2pcs acetate tape as the following picture.
  • Page 9 4. Disassembly and Assembly Procedures Assemble the front bezel with the assembled unit, then u se a Philips-head screwdriver to tighten 2pcs screws(left and right) for locking the front bezel. (No.1~2 Screw size= M3x0.5x4, Torque=3~4kgfxcm) Stick 1pcs aluminum foil on the specific position to fix the function key cable as the picture below shown.
  • Page 10 4. Disassembly and Assembly Procedures Move the assembled rear cover close to the Take a stand base close to the monitor. Fit the two panel unit, then connect the USB FFC cable to tabs on the upper part of the stand into the grooves on the connector of interface board.
  • Page 11 While in self-test mode, the power LED remains white. Also, depending upon the selected input, one of the dialogs shown below will continuously scroll through the screen. Dell UltraSharp 24/27 Monitor No DP Cable The display will go into Standby Mode in 4 minutes.
  • Page 12: Built-In Diagnostics

    5. Trouble Shooting Instructions Built-in Diagnostics Your monitor has a built-in diagnostic tool that helps you determine if the screen abnormality you are experiencing is an inherent problem with your monitor, or with your computer and video card. NOTE: You can run the built-in diagnostics only when the video cable is unplugged and the monitor is in self-test mode.
  • Page 13 1 Ensure that your PC is powered off. 2 Press any control button other than the power button to display the shortcut menu of Input Source. 3 Use the button to highlight USB Type-C. Dell UltraSharp 27 Monitor Input Source: Auto USB Type-C HDMI 4 Press and hold the button for approximately 8 seconds.
  • Page 14: Common Problems

    Missing Pixels LCD screen has • Cycle power on-off. spots • Pixel that is permanently off is a natural defect that can occur in LCD technology. • For more information on Dell Monitor Quality and Pixel Policy, see Dell Support site at: www.dell.com/support/monitors. Stuck-on Pixels LCD screen has • Cycle power On-Off. bright spots • Pixel that is permanently off is a natural defect that can occur in LCD technology.
  • Page 15: Product Specific Problems

    5. Trouble Shooting Instructions Common What You Possible Solutions Symptoms Experience Missing Color Picture missing • Perform monitor self-test. color • Ensure that the video cable connecting the monitor to the computer is connected properly and is secure. • Check for bent or broken pins in the video cable connector.
  • Page 16 • If the Notebook requires a >65 W power adaptor, it laptop, and so on may not charge with the USB Type-C connection. • Ensure that you use only Dell approved adapter or the adapter that comes with the product. • Ensure that the USB Type-C cable is not damaged.
  • Page 17 5. Trouble Shooting Instructions Problem What you Possible solutions experience The LAN port is OS setting or • Ensure that the latest BIOS and drivers for your not functioning cable connection computer are installed on your computer. issue • Ensure that the RealTek Gigabit Ethernet Controller is installed in the Windows Device Manager.