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

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

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.

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