Dell U4021QW User manual

Version: 01
Date: 2021/10/30
Service Manual - U4021QW

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
NOTE:
For replacement of power cord, connectivity cable and external power supply (if applicable), contact Dell:
1. Go to https://www.dell.com/support.
2. Verify your country or region in the Choose A Country/Region drop-down menu at the bottom-right corner of the page.
3. Click Contact Us next to the country dropdown.
4. Select the appropriate service or support link based on your need.
5. Choose the method of contacting Dell that is convenient for you.
Item Description Q'ty Remark
1 1
For EMEA Only, not for
other regions
2
Safety Mylar
1
13
4 1
15
6
Speaker
1
1 7
8 1
9
12
13 1
114
1 15
1 16
USB BD
Panel
Key BD
LED driver BD
Interface BD
1
1
17 1
1
Power BD ASSY
18
See “NOTE”
See “NOTE”
ASSY RISSER
See “NOTE”
See “NOTE”
Super Speed USB 3.2 Gen1 A to B
Power cable
ASSY BASE
ASSY Middle Frame
119 See “NOTE”
Thunderbolt™ 4 (USB Type-C) Active cable
HDMI cable
DisplayPort cable
Joystick BD
10 1
11
Main bracket ASSY
1
Rear Cover
17
16 18
15
19

3. Wiring Connectivity Diagram

4. How to connect and disconnect power cable/ connectivity cable
WARNING: To change power cable/ connectivity cable, switch off power before unplugging the cable and replugging in required
cable.

4. How to connect and disconnect power cable/ connectivity cable

5. Disassembly and Assembly Procedures
5.1 Disassembly Procedures:
Tool Required:
List the type and size of the tools that would typically can be
used to disassemble the product to a point where components
and materials requiring selective treatment can be removed.
Tool Description:
- Screwdriver(Phillip head) #1
- Screwdriver(Phillip head) #2
- Penknife
- Soldering iron and absorber
NOTE:
This “Disassembly and Assembly Procedures” is for EMEA only,
not for other regions. Please note that Dell will deem warranty void
if any disassembly is done on the monitors.
S2
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.
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.
Use a Philips-head screwdriver to remove 4pcs
screws for unlocking mechanisms.
(No.1~4 screw size=M4x11; Torque=11±1kgfxcm)
23
41
5
2
13
4
S4
Lift the rear cover up carefully. Disconnect the
joystick cable away from the connector, and tear off
1pcs aluminum foil, and then remove the rear cover.
Use a Philips-head screwdriver to remove 2pcs
screw for unlocking the joystick board, then release
the joystick board by tear off the tapes.
(No.1~2 screw size=M2x2.4, Torque=1±0.2kgfxcm)
1
2
Use a Philips-head screwdriver to remove 8pcs
screws for unlocking the speakers with middle bezel.
Release the speakers’ cables from the hooks of the
middle bezel, and then disconnect the speaker cable
away from the connector of the circuit board.
(No.1~8 screw size=M3x8, Torque=5±0.5kgfxcm)
S7
Disconnect the FFC cable and EDP cable away from
the connectors of the board. Use a Philips-head
screwdriver to remove 1pcs screw for unlocking the
USB board, then release the USB board from hooks.
(No.1 screw size=M3x6, Torque=5±0.5kgfxcm)
S6
1
2
6
7
8
53
4
1
S5

5. Disassembly and Assembly Procedures
S10
Put the middle bezel with LED board on a cushion,
and then release the cable by tearing off the tapes.
Tear off 1pcs mylar tape on the LED board, then
release the LED board from the pins of the middle
bezel.
Remove the two speakers U. se a Philips-head
screwdriver to remove 21pcs screws for unlocking
the middle bezel, then disconnect the LED cable
away from the board, and then remove the bezel.
(No.1~21 Screw size= M3x5, Torque=5±0.5kgfxcm)
S8
1
4
16
14
15
3
6
10
11
12
20
19
18
21 56
2
78
9
13
17
Tear off 2pcs aluminum foil for releasing the panel
lamp cable, and then u
. U
to remove 2pcs screws for unlocking the
heat-sink with the board. Disconnect the lamp cable
away from the connector of the board.
se a Philips-head screwdriver
to remove 5pcs screws for unlocking the bracket
chassis module with the panel se a Philips-head
screwdriver
(No.1~7 Screw size= M3x5, Torque=5±0.5kgfxcm)
S9
S11
Lift up the bracket chassis, and tear of the tape and
disconnect the LVDS cable from the connector of the
T-CON board of panel module, then put the bracket
chassis on a protective cushion.
4
2
3
1
6
5
7

5. Disassembly and Assembly Procedures
Use a Philips-head screwdriver to remove
screws for unlocking power board, interface board
and LED driver board.
8pcs
(No.1 screw size=M4x8, Torque=6±0.5kgfxcm;
No.2~8 screw size=M3x7.5, Torque=6±0.5kgfxcm)
Remove the LED driver board, interface board abd
power board from the
disconnect all of the cables.
bracket chassis module
carefully, and then
S14
S15
Tear off 2pcs shading tapes, and then disconnect
the panel lamp cable from the two connectors of the
panel module.
S12
Remove the mylar tape from the hooks of the
bracket .
41
3
2
7
6
58
S13

5. Disassembly and Assembly Procedures
5.2 Assembly Procedures:
Place a bracket chassis base on a protective
cushion, then stick 3pcs Silicon sheets on the
position as the picture below shown.
S2
S1
S4
S3
Panel preparation: Take out 1pcs panel module from
the carton, remove the protective film by tearing off
all the tapes of screen and four sides, then examine
the panel surface according to inspection criteria
carefully. Provide the power source to the panel
module to make sure the panel can be powered on.
S5
Take 1pcs Dell nameplate, then use a locating fixture
to fix the nameplate to the front bezel of the module,
and then move the whole unit into a laminating
fixture, use the laminating fixture to press the
nameplate with the front bezel of the panel module
firmly attachment.
S6
Turn over a power board and put the power board
into the bracket chassis.
Take 1pcs interface board, connect 1pcs LVDS cable
to the interface board, then connect the power board to
the interface board. Turn over the interface board and
locate it into the bracket. Take 1pcs LED driver board
to connect with the power board, turn over the board
and locate it into the bracket. Use a Philips-head
screwdriver to tighten 8pcs screws for locking the
interface board, power board and LED driver board.
(No.1 screw size=M4x8, Torque=7.5±0.5kgfxcm;
No.2~8 screw size=M4x8, Torque=7.5±0.5kgfxcm)
41
3
2
7
6
58
Take a black mylar to insert the hooks of the bracket
to cover the power board.

5. Disassembly and Assembly Procedures
Take 1pcs LED board and 1pcs middle bezel, and
then tear off the glue paper of the LED board, locate
the LED board into the pins of the middle bezel, and
then paste 1pcs mylar tape to fix the LED board, then
tear off the 2pcs papers on the back of the LED
cable, and fix the cable on the bezel with 2pcs tapes.
Adjust the bracket chassis module, and then u
,
tighten 2pcs screws for locking the heat-sink with the
board. Paste 2pcs aluminum foil on the specific
position to fix the lamp cable.
se a
Philips-head screwdriver to tighten 5pcs screws for
locking the bracket chassis module with the panel
(No.1~7 Screw size= M3x5, Torque=5±0.5kgfxcm)
S8
Move the bracket chassis module close to the panel
module, then connect the LVDS cable to the
connector of the T-Con board, then put the bracket
on the back of the panel module. Connect the panel
lamp cable to the connector of the board.
S9
S10
Turn over the panel module to place screen faced
down. Paste 2pcs shading tape on the top side of the
panel connectors as the picture below shown, then
take 1pcs panel lamp to plug the two connectors of
the panel module, then cover the two connectors with
shading tapes on the top side.
S7
4
2
3
1
6
5
7

5. Disassembly and Assembly Procedures
Take a pair of speakers to locate the probers of the
middle bezel, then locate the speakers’ cable to the
hooks of the middle bezel, and then connect the
speaker cable to the connector of the circuit board,
then fix the speakers’ cable with 2pcs acetate tapes.
Use a Philips-head screwdriver to tighten 8pcs
screws for locking the speakers with middle bezel.
(No.1~8 screw size=M3x8, Torque=6±1kgfxcm)
S12
Take 1pcs joystick key, 1pcs joystick board and 1pcs
rear cover, then assemble the joystick key with the
board. Locate the joystick board to the correct position
of the rear cover, then use a Philips-head screwdriver
to tighten 2pcs screws for locking the joystick board
with rear cover. Tear off the papers on the back of the
cable, and then fix the joystick cable with tapes.
(No.1~2 screw size=M2x2.4,Torque=1±0.2kgfxcm)
S14
2
6
7
8
53
4
1
Take 1pcs USB board, 1pcs conductive foam, 1pcs
FFC cable and 1pcs EDP cable. Connect the two
cables to the connectors of the USB board, then
paste 1pcs conductive foam on the back of the USB
board, and then locate the USB board into the
hooks of the middle bezel. Connect the FFC and
EDP cables to the circuit board. Use a Philips-
head screwdriver to tighten 1pcs screw for locking
the USB board.
(No.1 screw size=M3x6, Torque=4±0.5kgfxcm)
Assemble the middle
module, and then connect the LED cable to the
connector of the circuit board. Adjust the middle
bezel for two parts firmly attachment, then u
bezel unit with the panel
se a
Philips-head screwdriver to tighten 21pcs screws for
locking the middle bezel with the panel module.
(No.1~21 Screw size= M3x5, Torque=5±0.5kgfxcm)
S11
1
4
16
14
15
3
6
10
11
12
20
19
18
21 56
2
78
9
13
17
S13
1

5. Disassembly and Assembly Procedures
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.
Use a protective bag to pack the stand base, then 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.
S17
S18
Use a Philips-head screwdriver to tighten four
screws for locking mechanisms. Stick 1pcs label on
the specific positions as the picture below shown.
(No.1~4 screw size=M4x11; Torque=11±1kgfxcm)
S16
23
41
Paste 1pcs aluminum foil to cover the connectors
as the picture below shown, then move the
assembled rear cover close to the panel unit,
then connect the joystick cable to the connector
of circuit board. Put down the rear cover and
push the rear cover on the positions marked as
the picture below shown for mechanisms
engagement.
S15
21

6. 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:
1. Turn o both your computer and the monitor.
2. Unplug 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.
3. Turn 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.
No DP Cable
The display will go into Standby Mode in 4 minutes.
www.dell.com/U4021QW
or
No HDMI 1 Cable
The display will go into Standby Mode in 4 minutes.
www.dell.com/U4021QW
or
No HDMI 2 Cable
The display will go into Standby Mode in 4 minutes.
www.dell.com/U4021QW
or
No Thunderbolt (90W) Cable
The display will go into Standby Mode in 4 minutes.
www.dell.com/U4021QW
4. This box also appears during normal system operation if the video cable
becomesdisconnected or damaged.
5. Turn 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.

6. 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.
Preset Modes
To run the built-in diagnostics:
1. Ensure that the screen is clean (no dust particles on the surface of the screen).
2. Press and hold Up or Down or Left or Right direction for four seconds until a
menu appears on the screen.
3. Using the joystick control, highlight the Diagnostics option and press the
joystick button to start the diagnostics. A gray screen is displayed.
4. Observe if the screen has any defects or abnormalities.
5. Toggle the joystick once again until a red screen is displayed.
6. Observe if the screen has any defects or abnormalities.
7. Repeat steps 5 and 6 until the screen displays green, blue, black, and white
colors. Note any abnormalities or defects.
The test is complete when a text screen is displayed. To exit, toggle the joystick control
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.
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.

6. Trouble Shooting Instructions
Common
Symptoms
What You
Experience
Possible Solutions
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/pixelguidelines.
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/pixelguidelines.
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.
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.

6. Trouble Shooting Instructions
Product specific problems
NOTE: ThunderboltTM is not supported Windows 7.
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.
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 Video or
display on HDMI
port
No video when
connecting
docking, dongle
or Blu-ray DVD
players
•Due to legacy platform cannot recognize or
output 5120 x 2160, we suggest to switch to
lower resolution to cover this compatibility
problem:
1. Remove all input cables, press and hold Up or
Down or Left or Right direction for 4 seconds .
(Please refer to Built-in Diagnostics for button
numbers)
2. Choose “Enable” on POP up screen to change
max resolution from 5120 x 2160 to 3840 x 2160.
Monitor
displayed image
at 2560 x 1080
@ 60Hz
Displayed
image not at
5120 x 2160 @
30Hz/60Hz
due to duplicate
mode
•Press “Windows” + “P” key, select either “Extend
Mode” or “second screen only”.
•Goto Display setting, select 5120x2160.
Monitor
displayed
image not at
5120x2160
Displayed image
not at 5120
x 2160 when
connected to
docking device
•To support 5120x2160, check whether docking
device meet either one of the following:
1.DP1.2 or higher
2.Type-C Alt Mode DP1.2 or higher
3. HDMI 2.0

6. Trouble Shooting Instructions
Problem What you
experience
Possible solutions
Black screen on
Chrome OS @
HDMI port
Black screen
after switch
on PBP mode
80/20
•Graphic Card Driver not able to support
resolution 4096 x 2160.
• Switch to PBP 75/25 or 50/50
No Display
or USB not
working
No Display
or USB not
working on
Windows 7
•Windows 7 not support. Switch to Windows 10.
Enter BIOS
setup menu @
HDMI port
Unable to goto
BIOS setup
menu
•unplug the HDMI cable or disconnect the
monitor
Black screen on
PBP mode @
HDMI
Switch to PBP
80/20 mode no
displayed image
@ HDMI when
connected to
Docking device
•Some docking device do not support 80/20
(4096 x 2160) resolution.
•Switch PBP mode to 75/25 or 50/50
•Plug/unplug HDMI cable
•Change input source to DP port
Display image at
5120 x 2160 @
30 Hz at HDMI
port
Not able to
select 5120
x 2160 @ 60
Hz in Graphic
Control Panel at
HDMI Port
•Due to legacy platform HDMI 2.0 HW bandwidth
limitation, it can only support 5120 x 2160 @ 30
Hz.
•Switch to DP 1.2 or higher
Monitor
displayed image
at 3840 x 2160
@ 60 Hz
Not able to
select 5120 x
2160 in Graphic
Control Panel
•Due to legacy platform HW limitation, it does not
support 5120 x 2160.
•To support 5120 x 2160 @ 60 Hz, check whether
the platform meet either one of the following:
1. DP1.2 or higher.
2. Type-C Alt Mode DP1.2 or higher.
3. HDMI 2.0.
Monitor displays
image at 3840
x 2160 @ 60 Hz
when using Intel
Graphic Card
Not able to
select 5120
x 2160 @ 60
Hz with: Intel
CPU Gen10 or
lower, and Intel
Graphic Driver
x.7584 onward.
•Intel Graphic Driver has disabled 5K Mode
Support from V7584 to 7916.
•Install/Re-install Intel Graphic driver after v.7925
or higher.
Monitor display
image at 5120 x
2160 @ 30Hz
when
connected to
Intel Graphic
Card via TBT
port
Not able to
select 5120
x 2160 @
60 Hz
•Due to legacy Intel CPU bandwidth limitation.
•Inte CPU 10th (Ice Lake) or Gen 11th (Tiger
Lake) or later CPU (DP 1.4) can support 5120 x
2160 @ 60 Hz.

6. Trouble Shooting Instructions
Problem What you
experience
Possible solutions
No image
when using
ThunderboltTM
3 connection
to computer,
laptop, and so
on
Black screen •Verify if the ThunderboltTM interface of the
device can support DP alternate mode.
•Verify if the device required more than 90 W
power charging.
•ThunderboltTM interface of device cannot
support DP alternate mode.
•Set Windows to Projection mode.
•Ensure that the ThunderboltTM 4 (USB Type-C)
active cable is not damaged.
No charging
when using
ThunderboltTM
3 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 >90 W power
adaptor.
•If the Notebook requires a >90 W power adaptor,
it may not charge with the ThunderboltTM 3
connection.
•Ensure that you use only Dell approved adapter
or the adapter that comes with the product.
•Ensure that the ThunderboltTM 4 (USB Type-C)
active cable is not damaged.
Intermittent
charging
when using
ThunderboltTM
3 connection to
computer,
laptop, and so
on
Intermittent
charging
•Check if the maximum power consumption of
device is over 90 W.
•Ensure that you use only Dell approved adapter
or the adapter that comes with the product.
•Ensure that the ThunderboltTM 4 (USB Type-C)
active cable is not damaged.
No image
when using
ThunderboltTM
connection to
the PC
Black screen •Verify which ThunderboltTM standard (DP 1.2
or DP 1.4) is your Graphics Card certied to.
Download and install the latest graphics card
driver.
•Some DP 1.2 graphics card cannot support DP
1.4 monitors. Go to OSD menu, under Input
Source selection, press and hold ThunderboltTM
select key for 8 sec to change the monitor
setting from DP 1.4 to DP 1.2.
No network
connection
Network
dropped or
Intermittent
•Do not toggle O/On the power button when
network is connected, keeps the power button
On.

6. 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
ThunderboltTM 4 (USB Type-C) active cable and
power cord of the monitor. Then, power on the
computer, plug in the monitor power cord and
ThunderboltTM 4 (USB Type-C) active cable.
Universal Serial Bus (USB) specific problems
Specific What You Possible Solutions
Symptoms Experience
USB interface is USB peripherals •Check that your display is turned ON.
not working are not working •Ensure USB Selection is set correctly in the USB
menu.
•Reconnect the upstream cable to your
computer.
•Reconnect the USB peripherals (downstream
connector).
•Turn o the monitor and turn it on again.
•Reboot the computer.
•Some USB devices like external portable HDD
require higher electric current; connect the
device directly to the computer system.
•Certain USB devices such as portable hard
drives require higher power source; connect the
drive to the computer directly.
•Disconnect one upstream USB cable when using
two upstream connections.