Dell U2421M User manual

Troubleshooting steps
Using the Monitor Self-Test
The 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 off both the computer and the monitor.
2. Unplug the video cable from the back of the monitor. To ensure proper Self-Test
operation, remove all digital (white DVI connector) and analog (blue VGA connector)
cables from the back of the computer.
3. Turn on the monitor.
The floating dialog box should appear on-screen (against a black background) if the flat panel
display cannot sense a video signal and is working correctly. While in self-test mode, the power
LED remains blue. Also, depending upon the selected input, one of the dialogs shown below will
continuously scroll through the screen.

4. This box also appears during normal system operation, if the video cable becomes
disconnected or damaged. The monitor will enter Power Save Mode after 5 minutes if
left at this state.
5. Turn off the flat panel display and reconnect the video cable; then turn on both the
computer and the flat panel display.
If the flat panel display screen remains blank after using the previous procedure, check the video
controller and computer, because the flat panel display is functioning properly.
Using the Built-In Diagnostics
The monitor has a built-in diagnostic tool that helps you determine if a problem you are having
with the display is a problem with the monitor, your computer, or your video card.
You can only run the built-in diagnostics when the video cable is unplugged and the monitor is
in self-test mode.
To run the built-in diagnostics:

Your monitor has a built-in diagnostic tool that helps to determine if the screen abnormality you
are experiencing is an inherent problem with the monitor, or with the computer and video card.
To run the built-in diagnostics:
1. Ensure that the screen is clean (no dust particles on the surface of the screen).
2. Unplug the video cable(s) from the back of the computer or monitor. The monitor then
goes into the self-test mode.
3. Press and hold Button 1 and Button 4 simultaneously for 2 seconds. A gray screen
should appear.
4. Carefully inspect the screen for abnormalities.
5. Press Button 4 on the front panel again. The color of the screen should change to red.
6. Inspect the screen for abnormalities.
7. Repeat steps 5 and 6 to inspect the display in green, blue, black, white, and text screens.

8. The test is complete when the white screen appears. To exit, press the Button 4 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 Monitor Issues
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.
No Video/Power LED
On
No picture or no
brightness
Increase the brightness and contrast controls
via OSD.
Run the 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 via the Input Source Select button.
Poor Focus
Picture is fuzzy,
blurry, or
ghosting
Eliminate video extension cables.
Reset the monitor to the Factory settings.
Change the video resolution to the correct
aspect ratio (16:9).
Shaky/Jittery Video
Wavy picture or
fine movement
Reset the monitor to Factory Settings.
Check the environmental factors.

Relocate the monitor and test it in another
room.
NOTE: If you're using DVI connection,
ensure that a Dual Link DVI cable is used
(supplied together with the monitor). Check
for loose connection. Unplug & reconnect if
required.
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 Pixel Policy, see Dell Support
site at: www.dell.com/support/monitors
.
Brightness Problems
Picture too dim
or too bright
Reset the monitor to the Factory settings.
Adjust the brightness/contrast controls via
OSD.
Geometric Distortion
Screen not
centered
correctly
Reset the monitor to Factory settings.

Horizontal/Vertical
Lines
Screen has one
or more lines
Reset the monitor to the Factory settings.
Perform monitor self-test feature check and
determine if these lines are also in self-test
mode.
Check for bent or broken pins in the video
cable connector.
Run the built-in diagnostics.
If you're using DVI connection, ensure that a
Dual Link DVI cable is used (Supplied
together with the monitor).
Check for loose connection. Unplug &
reconnect if required.
Synchronization
Problems
Screen is
scrambled or
appears torn
Reset the monitor to the Factory settings.
Perform monitor self-test feature check to
determine if the scrambled screen appears in
self-test mode.
Check for bent or broken pins in the video
cable connector.
Restart the computer in the safe mode.
If you're using DVI connection, ensure that a
Dual Link DVI cable is used (Supplied
together with the monitor).
Check for loose connection. Unplug &
reconnect if required.
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 the 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 feature check.
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 is
not good
Change the Color Setting mode in the Color
Settings OSD to Graphics or Video,
depending on the application.
Try different Color Preset Settings in Color
Settings OSD. Adjust R/G/B value in Color
Settings OSD if the Color Management is
turned Off.
Change the Input Color Format to PC RGB
or YPbPr in the Advance Settings 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 appears
on the screen
Use the Power Management feature to turn
off the monitor at all times, when it is not in
use. (for more information, see Power
Management Modes).
Alternatively, use a dynamically changing
screensaver.

Product Specific Issues
Specific
Symptoms
What You
Experience
Possible Solutions
Screen image is too
small
Image is centered
on screen, but does
not fill entire
viewing area
Check the Scaling Ratio setting in Image
Setting 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 Off the monitor, unplug the power cord,
plug back, and then turn on the monitor.
Check whether OSD is locked. If yes, press
and hold button above power button for 10
seconds to unlock. See Menu Lock.
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. Re-plug the signal cable 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 different video formats (aspect ratio)
of DVDs, the monitor may display in full
screen.
Run the built-in diagnostics.
No image when
using DP
connection to the
PC
Black screen
Verify which DP standard (DP 1.1a or DP 1.2)
is your Graphics Card certified to. Download
and install the latest Graphics Card driver.
Some DP 1.1a Graphics Card cannot support
DP 1.2 monitors. Change the monitor DP

setting to match your Graphics Card by
following instruction found in section
"Connecting the Monitor For DP MST
Function".
When choosing DVI-D/DP/DVI/HDMI mode, the Auto Adjust function will not be available.
USB Issues
Specific
Symptoms
What User Experience
Possible solution
USB interface is
not working
USB peripherals are not
working
Check that your monitor is turned ON.
Reconnect the upstream cable to your
computer.
Reconnect the USB peripherals
(downstream connector).
Switch off and then turn on the monitor
again.
Reboot the computer.
Some USB devices like external portable
HDD require higher electric current;
connect the device directly to the
computer system.
High Speed USB
3.0 interface is
slow.
High Speed USB 3.0
peripherals working
slowly or not working at
all
Check that your computer is USB 3.0-
capable.
Some computers have both USB 3.0,
USB 2.0 and USB 1.1 ports. Ensure that
the correct USB port is used.
Reconnect the upstream cable to your
computer.
Reconnect the USB peripherals
(downstream connector).

Reboot the computer.
Sound bar Issues
Common
Symptoms
What You
Experience
Possible Solutions
No Sound
No power to
Soundbar —the
power indicator is
Off.
Turn the Power/Volume knob on the Soundbar
clockwise to the middle position; check if the
power indicator (Blue LED) on the front of the
Soundbar is illuminated.
Confirm that the power cable from the Soundbar
is plugged into the adapter.
No Sound
Soundbar has power
- power indicator is
On.
Plug the audio line-in cable into the computer's
audio out jack.
Set all Windows volume controls to their
maximum.
Play some audio content on the computer (i.e.
audio CD, or MP3).
Turn the Power/Volume knob on the Soundbar
clockwise to a higher volume setting.
Clean and reseat the audio line-in plug.
Test the Soundbar using another audio source (i.e.
portable CD player).
Distorted
Sound
Computer's sound
card is used as the
audio source.
Clear any obstructions between the Soundbar and
the user.
Confirm that the audio line-in plug is completely
inserted into the jack of the sound card.
Set all Windows volume controls to their
midpoints.
Decrease the volume of the audio application.

Turn the Power/Volume knob on the Soundbar
counter-clockwise to a lower volume setting.
Clean and reseat the audio line-in plug.
Troubleshoot the computer's sound card.
Test the Soundbar using another audio source (i.e.
portable CD player).
Distorted
Sound
Other audio source is
used.
Clear any obstructions between the Soundbar and
the user.
Confirm that the audio line-in plug is completely
inserted into the jack of the audio source.
Decrease the volume of the audio source.
Turn the Power/Volume knob on the Soundbar
counter-clockwise to a lower volume setting.
Clean and reseat the audio line-in plug.
Unbalanced
Sound Output
Sound from only one
side of Soundbar.
Clear any obstructions between the Soundbar and
the user.
Confirm that the audio line-in plug is completely
inserted into the jack of the sound card or audio
source.
Set all Windows audio balance controls (L-R) to
their midpoints.
Clean and reseat the audio line-in plug.
Troubleshoot the computer's sound card.
Test the Soundbar using another audio source (i.e.
portable CD player).
Low Volume
Volume is too low.
Clear any obstructions between the Soundbar and
the user.
Turn the Power/Volume knob on the Soundbar
clockwise to the maximum volume setting.
Set all Windows volume controls to their
maximum.
Increase the volume of the audio application.

Test the Soundbar using another audio source (i.e.
portable CD player).
Cardreader Issues
Problems
Cause
Solution
Drive letter is not
assigned. (Windows®
XP only)
Conflict with network drive letter.
A. Right-click My
Computer on the desktop,
and then click Manage.
Under Computer
Management, click Desk
Management.
B. In the list of drives in the
right panel, right-click
Removable Device and then
click Change Drive Letter
and Paths.
C. Click Change, and in the
drop-down box, specify a
drive letter for the
Removable Device,
choosing one that is not
assigned to the mapped
network drives.
D. Click OK, then click OK
again
Drive letter is
assigned, but the media
is not accessible
The media needs reformatting.
Right-click the drive in
Explorer and choose
Format from the resulting
menu.

The media has been
ejected during writing
or erasing.
Displays the error message, "Error
copying file or folder."
Displays the error message,
"Cannot write folder (folder name)
or file (file name)," during writing,
or, "Cannot remove folder (folder
name) or file (file name),". While
erasing, you cannot write or erase
in the same folder or file name.
Reinsert the media and
write or erase again.
Format the media for
writing or erasing the same
folder or file name.
Despite the
disappearance of the
pop-up window, the
media has been ejected
while the LED was
blinking.
Although the pop-up window
disappears during writing, if you
eject your media while the LED is
still blinking, then you cannot
complete your action on the media.
Format the media for
writing or erasing the same
folder
or file name.
Cannot format or write
on the media.
Write protect switch is enabled.
Verify that the write-
protect switch of the media
is unlocked.
Card reader is not
working
USB interface is not working.
Check that your monitor is
powered On.
Reconnect the upstream
cable from your computer
to the monitor.
Reinsert the media.
Switch Off and then turn
On the monitor again.
Reboot the computer.
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procedure or advice set out in the Quick Tips.
Article ID: SLN297700