Dell UltraSharp U2421HE User manual

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.
! To ensure using a proper screwdriver, follow the
torque and force listed in assembly and
disassembly procedures to unscrew screws.
! Using Lead-Free solder to well mounted the
parts.
! The fusion point of Lead-Free solder requested in
the degree of 220°C.
1. Important Safety Notice

2. Exploded view diagram with list of items
Panel
Power Button
OSD Button
Front trim
Key board
Key mylar
Power myalr
Power board
Interface board
Stand
Back Cover
Main chassis
Key Board

3. Wiring Connectivity Diagram
Audio out
LED DRIVER
HDMI1 DP1 DP2 USB1 USB2 USB3
Panel
Interface board
FK board
USB board

4. Disassembly and Assembly Procedures
S2
4.1 Disassembly Procedures:
S1
S3
Remove the monitor stand base:
1. Place the monitor on a soft cloth or cushion.
2. Press and hold the stand-release button.
3. Lift the stand up and away from the monitor.
Use a Philips-head screwdriver to remove four
screws for unlocking mechanisms.
(No.1~4 screw size=M4x11; Torque=11±1kgfxcm)
S2
23
41
Wedge your fingers between the rear cover and the
middle bezel on the corners of the top side of the
monitor to release the rear cover, then use one hand
to press the middle bezel, the other hand to pull up
carefully the rear cover in order of arrow preference
for unlocking mechanisms of rear cover.
1
2
3
Necessary repair and test equipment:
1. Philips-head screwdriver
S6
S5
S7
S4
Use a Philips-head screwdriver to remove one screw
for unlocking the USB board unit, then release the
USB board unit and put it aside.
(No.1 screw size=M3x6, Torque=4±0.5kgfxcm)
1
Lift the rear cover up carefully. Disconnect the USB
FFC cable from the connector of the interface board,
and then remove the rear cover.
Tear off 1pcs aluminium foil for unfixing the function
key cable.
Tear off 2pcs acetate tape for releasing the panel
lamp cables. Use a proper tool to release the
function key cable from the connector, then pull the
function key cable high for releasing the function key
cable as the picture below shown.

4. Disassembly and Assembly Procedures
S9
S8
U
.
se a Philips-head screwdriver to remove 2pcs
screws(left and right) for unlocking the front bezel
with the panel module, then disassemble the front
bezel with the unit and put it aside
(No.1~2 Screw size= M3x0.5x4, Torque=3~4kgfxcm)
1
2
Tear off the mylar tape on the function key board,
then use a Philips-head screwdriver to tighten 3pcs
screws for locking the function key board with the
front bezel.
(No.1~3 Screw size= M2x2.4, Torque=1±0.2kgfxcm)
1
2
3
S10
S11
S12
S13
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)
35
24
1
Tear off 2pcs acetate tapes for releasing the panel
lamp cables, then unplug the panel lamp cables from
the connectors of the panel module and power board.
Use a Philips-head screwdriver to remove 4pcs
screws for unlocking the bracket chassis module.
(No.1~4 Screw size= M3x0.5x3, Torque=5~6kgfxcm)
23
4
1
Disconnect the LVDS cable from the connector of
the panel module. Lift up the bracket chassis, and
then put the bracket chassis on a protective cushion.

4. Disassembly and Assembly Procedures
Remove the circuit boards from the
disconnect all of the cables.
bracket
carefully, and then
S15
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.
two
(No.1~2 screw size=M3x10, Torque=6±0.5kgfxcm)
S16
S14
21
Use a Philips-head screwdriver to remove screws
for unlocking power board and interface board.
7pcs
(No.1 screw size=M4x8, Torque=6±0.5kgfxcm;
No.2~7 screw size=M3x7.5, Torque=6±0.5kgfxcm)
2
1
4
4
5
6
7

4. Disassembly and Assembly Procedures
4.2 Assembly Procedures:
Turn over a power board and put the power board
into the bracket chassis, settle the panel power
cable to the correct position.
Place a bracket chassis base on a protective
cushion, then stick 6pcs Silicon sheets on the
positions as the picture below shown.
S2
S1
Use a two screws
for locking the AC-power outlet connector. Take a
mylar to insert the hooks of the bracket to cover the
power board.
Philips-head screwdriver to tighten
(No.1~2 screw size=M3x8, Torque=6~8kgfxcm)
S4
Take a interface board, connect 1pcs LVDS cable to
the connector of the interface board, then connect
the cable of the power board to the connector of the
interface board. Turn over the interface board and
locate it into the bracket. Use a Philips-head
screwdriver to tighten 6pcs screws for locking the
interface board.
(No.1 screw size=M4x8, Torque=6±0.5kgfxcm)
1
S3
21
S5
7
6
5
2
3
4
Take 1pcs driver board, connect the correct cables of
the power board to the connector of the driver board,
then turn over the driver board and locate it into the
bracket. Use a Philips-head screwdriver to tighten
6pcs screw for locking power board, interface board
and the driver board with the bracket chassis, then
locate the cables to the hooks of the bracket chassis
module.
(No.2~7 screw size=M4x8, Torque=6±0.5kgfxcm)

4. Disassembly and Assembly Procedures
S8
S9
Adjust the bracket chassis module, and then u
.
se a
Philips-head screwdriver to tighten 4pcs screws for
locking the bracket chassis module with the panel
(No.1~4 Screw size= M3x0.5x3, Torque=5~6kgfxcm)
23
4
1
S10
S7
1
2
3
Panel preparation: Take out 1pcs panel module from
the carton, remove the protective film by tearing off
the tapes, then Examine the panel surface
according to inspection criteria. Turn over the panel
to place screen faced down for later assembling.
Move the bracket chassis module close to the panel
module, then connect the LVDS cable to the
connector of the panel module, then turn over the
bracket chassis and put it on the back of the bracket
chassis module.
S6
Connect the panel power cables to the two
connectors of the panel module, then fix the cables
with 2pcs acetate tape as the following picture.
Take 1pcs function key board, 1pcs lens and 1pcs
middle bezel, assemble the lens with the front bezel,
and then locate the function board into the specific
position of the front bezel. Put the unit into a fixture,
use
Stick 1pcs mylar tape to cover the
function key board.
a Philips-head screwdriver to tighten 3pcs
screws for locking the function key board with the
front bezel.
(No.1~3 Screw size= M2x2.4, Torque=1±0.2kgfxcm)

4. Disassembly and Assembly Procedures
Use a Philips-head screwdriver to tighten 5pcs
screws for locking the front bezel with the panel.
(No.1~5 screw size=M2x2.7, Torque=3±0.5kgfxcm)
Stick 2pcs acetate tape to fix the panel lamp cables.
Tear off all the double-faced adhesive tapes which
sticked on the back of the function key cable, and
then fix the cables with the double-faced tape. Use a
proper tool to connect the function key cable to the
connector of the interface board.
S12
2
S11
Assemble the front
then u
bezel with the assembled unit,
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)
1
35
24
1
S13
S14
Take a USB board, a USB hub and a connect cable.
Connect the cable to the USB board, then locate the
USB board into the USB hub. Stick 1pcs aluminum
foil on one side of the USB hub, then locate the
USB unit into the hook of a rear cover. Use a
Philips-head screwdriver to tighten one screw for
locking the USB unit with the rear cover. Tear off the
adhesive paper of the left and right side of rear cover.
(No.1 screw size=M3x6, Torque=4±0.5kgfxcm)
S15
1
Stick 1pcs aluminum foil on the specific position to fix
the function key cable as the picture below shown.

23
41
Move the assembled rear cover close to the
panel unit, then connect the USB FFC cable to
the connector of interface board. Put down the
rear cover and push the rear cover on the
positions marked as the picture below shown for
mechanisms engagement.
S16
Use a Philips-head screwdriver to tighten 4pcs
screws for locking the rear cover with the assembled
unit. Stick two pieces of label on the specific
positions, then insert a DP out Cap into the DP out
connector.
(No.1~4 screw size=M4x10; Torque=9±0.5kgfxcm)
S17
Take a stand base close to the monitor. Fit the two
tabs on the upper part of the stand into the grooves on
the back of the monitor, and then lower the stand so
that the monitor mounting area snaps onto the stand.
Lift up the monitor to checking the gap between the
front bezel with panel module , then provide power
supply and a video signal to the monitor , then turn on
the monitor for functionality check.
S18
S19
4. Disassembly and Assembly Procedures

5. Trouble Shooting Instructions
Self-Test
Your monitor provides a self-test feature that allows you to check whether your monitor is
functioning properly. If your monitor and computer are properly connected but the monitor
screen remains dark, run the monitor self-test by performing the following steps:
1Turn o both your computer and the monitor.
2Unplug the video cable from the back of the computer. To ensure proper Self-Test
operation, remove all digital and the analog cables from the back of computer.
3Turn on the monitor.
The floating dialog box should appear on-screen (against a black background), if the monitor
cannot sense a video signal and is working correctly. 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
The display will go into Standby Mode in 4 minutes.
No DP Cable
www.dell.com/support/U2421HE
www.dell.com/support/U2721DE
U2421HE/U2721DE
or
Dell UltraSharp 24/27 Monitor
The display will go into Standby Mode in 4 minutes.
No USB Type-C Cable
www.dell.com/support/U2421HE
www.dell.com/support/U2721DE
U2421HE/U2721DE
4This box also appears during normal system operation if the video cable becomes
disconnected or damaged.
5Turn o your monitor and reconnect the video cable; then turn on both your
computer and the monitor.
If your monitor screen remains blank after you use the previous procedure, check your video
controller and computer, because your monitor is functioning properly.

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.
3 4 51 2
To run the built-in diagnostics:
1Make sure that the screen is clean (no dust particles on the surface of the screen).
2Unplug the video cable(s) from the back of the computer or monitor. The monitor
then goes into the self-test mode.
3Press and hold Button 1 for 5 seconds. A gray screen appears.
4Carefully inspect the screen for abnormalities.
5Press Button 1 on the front panel again. The color of the screen changes to red.
6Inspect the display for any abnormalities.
7Repeat steps 5 and 6 to inspect the display in green, blue, black, white, and text
screens.
The test is complete when the text screen appears. To exit, press Button 1 again.
If you do not detect any screen abnormalities upon using the built-in diagnostic tool, the
monitor is functioning properly. Check the video card and computer.

5. Trouble Shooting Instructions
Setting USB-C Prioritization when USB-C Charging is
set to On During Power Off
If USB-C Charging is set to On During Power Off, the monitor allows you to specify the
USB-C Prioritization settings only when your PC is powered off.
1Ensure that your PC is powered off.
2Press any control button other than the power button to display the shortcut menu
of Input Source.
3Use the or button to highlight USB Type-C.
Dell UltraSharp 27 Monitor
Input Source: Auto
USB Type-C
DP
HDMI
4Press and hold the button for approximately 8 seconds.
5The USB-C Prioritization configuration message will appear.
Dell UltraSharp 27 Monitor
Select USB-C Prioritization:
High Resolution
U2721DE
High Data Speed
6Use the or button to specify the preferred transfer priority.
7The setting will be effective after you turn on the PC.

5. Trouble Shooting Instructions
Common Problems
The following table contains general information about common monitor problems you might
encounter and the possible solutions:
Common
Symptoms
What You
Experience
Possible Solutions
No Video/Power
LED off
No picture •Ensure that the video cable connecting the monitor
and the computer is properly connected and secure.
•Verify that the power outlet is functioning properly
using any other electrical equipment.
•Ensure that the power button is depressed fully.
•Ensure that the correct input source is selected in
the Input Source menu.
No Video/Power
LED on
No picture or no
brightness
•Increase brightness and contrast controls via OSD.
•Perform monitor self-test feature check.
•Check for bent or broken pins in the video cable
connector.
•Run the built-in diagnostics.
•Ensure that the correct input source is selected in
the Input Source menu.
Missing Pixels LCD screen has
spots
•Cyclepoweron-off.
•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
bright spots
•CyclepowerOn-Off.
•Pixelthatispermanentlyoffisanaturaldefect
that can occur in LCD technology.
•FormoreinformationonDellMonitorQuality
and PixelPolicy, see Dell Support site at:
www.dell.com/support/monitors.
Brightness
Problems
Picture too dim
or too bright
•Reset the monitor to factory settings.
•Adjust brightness and contrast controls via OSD.
Safety Related
Issues
Visible signs of
smoke or sparks
•Do not perform any troubleshooting steps.
•Contact Dell immediately.
Intermittent
Problems
Monitor
malfunctions on
& off
•Ensure that the video cable connecting the monitor
to the computer is connected properly and is
secure.
•Resetthemonitortofactorysettings.
•Perform monitor self-test feature check to
determine if the intermittent problem occurs in self-
test mode.

5. Trouble Shooting Instructions
Common
Symptoms
What You
Experience
Possible Solutions
Missing Color Picture missing
color
•Perform monitor self-test.
•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.
Wrong Color Picture color not
good
•Change the settings of the Preset Modes in the
Color menu OSD depending on the application.
•Adjust R/G/B value under Custom Color in Color
menu OSD.
•Change the Input Color Format to PC RGB or
YPbPr in the Color menu OSD.
•Run the built-in diagnostics.
Image retention
from a static
image left on
the monitor for
a long period of
time
Faint shadow
from the static
image displayed
appears on the
screen
•Set the screen to turn o after a few minutes of
screen idle time. These can be adjusted in Windows
Power Options or Mac Energy Saver setting.
•Alternatively, use a dynamically changing
screensaver.
Product Specific Problems
Problem What you
experience
Possible solutions
Screen image is
too small
Image is
centered on
screen, but does
not fill entire
viewing area
•Check the Aspect Ratio setting in the Display
menu OSD.
•Reset the monitor to factory settings.
Cannot adjust
the monitor with
the buttons on
the front panel
OSD does not
appear on the
screen
•Turn o the monitor, unplug the monitor power
cable, plug it back, and then turn on the monitor.
No Input Signal
when user
controls are
pressed
No picture, the
LED light is white
•Check the signal source. Ensure the computer is
not in the power saving mode by moving the mouse
or pressing any key on the keyboard.
•Check whether the signal cable is plugged in
properly. Connect the signal cable again, if
necessary.
•Reset the computer or video player.

5. Trouble Shooting Instructions
Problem What you
experience
Possible solutions
The picture does
not fill the entire
screen
The picture
cannot fill the
height or width
of the screen
•Due to dierent video formats (aspect ratio) of
DVDs, the monitor may display in full screen.
•Run the built-in diagnostics.
No image
when using
USB Type-C
connection
to computer,
laptop, and so on
Black screen •Verify if the USB Type-C interface of the device can
support DP alternate mode.
•Verify if the device required more than 65 W power
charging.
•USB Type-C interface of device cannot support DP
alternate mode.
•Set Windows to Projection mode.
•Ensure that the USB Type-C cable is not damaged.
No charging
when using
USB Type-C
connection
to computer,
laptop, and so on
No charging •Verify if the device can support one of 5 V/9 V/15
V/20 V charging proles.
•Verify if the Notebook requires a >65 W power
adaptor.
•If the Notebook requires a >65 W power adaptor, it
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.
Intermittent
charging
when using
USB Type-C
connection to
computer,
laptop, and so on
Intermittent
charging
•Check if the maximum power consumption of
device is over 65 W.
•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.
No image
when using DP
connection to
the PC
Black screen •Verify which DP standard (DP 1.1a or DP 1.4) is your
Graphics Card certied to. Download and install the
latest graphics card driver.
•Some DP 1.1a graphics card cannot support
DP 1.4 monitors. Go to OSD menu, under Input
Source selection, press and hold DP select
key for 8 sec to change the monitor setting from
DP 1.4 to DP 1.1a.
No image when
using USB
Type-C MST
Black screen or
2nd DUT is not
Prime mode
•USB Type-C input, Go to OSD menu, under Display
Info check the Link Rate is HBR2 or HBR3, if Link
Rate is HBR2, suggest to use USB Type-C to DP
cable to turn on MST.
No network
connection
Network
dropped or
Intermittent
•check to ensure data priority is selected in OSD. Do
not toggle O/On the power button when network
is connected, keeps the power button On.

5. Trouble Shooting Instructions
Problem What you
experience
Possible solutions
The LAN port is
not functioning
OS setting or
cable connection
issue
•Ensure that the latest BIOS and drivers for your
computer are installed on your computer.
•Ensure that the RealTek Gigabit Ethernet Controller
is installed in the Windows Device Manager.
•If your BIOS Setup has a LAN/GBE Enabled/
Disabled option, make sure it is set to Enabled.
•Ensure that the Ethernet cable is connected
securely on the monitor and the hub/router/rewall.
•Check the status LED of the Ethernet cable to
conrm connectivity. Re-connect both ends of the
Ethernet cable if the LED is not lit.
•First power o the Computer and unplug the
Type-C cable and power cord of the monitor. Then,
power on the computer, plug in the monitor power
cord and Type-C cable.