For help with video or display issues such as no video or no display, blank or black screen, flickering, resolution or color issues, horizontal or vertical lines, so on see an expanding section below.
The key features of the Dell UltraSharp U2421HE and U2721DE monitor are:
This section provides some specifications of the Dell UltraSharp U2421HE and U2721DE monitor. To learn more about the specifications of the Dell UltraSharp U2421HE and U2721DE monitor, see the User's Guide at the Dell Manuals website.
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Panel technology |
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Maximum resolution |
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Viewing angle |
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Response time |
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Color gamut |
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Color depth |
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Ports and connectors |
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Ensuring that your Dell monitor is set up properly. Assembling the monitor stand and set up the monitor ergonomically. Connecting the cables and organizing them. These will only help make the viewing experience the best it possibly can be.
The standard monitor stand is detached when the monitor is shipped from the factory. To learn more about attaching the standard monitor stand. See the Setting Up the Monitor section in the User's Guide of your Dell UltraSharp U2421HE and U2721DE Monitor.
To learn how to set up any other stand with a monitor, see the respective stand setup guide for setup instructions.
Where you put your monitor is almost as important as what model you buy. The monitor should be directly in front of you, at an arm’s length away (between 20-40 inches from your eyes). Set the top edge of the screen at eye level when you are sitting comfortably. Adjust your chair height or the height of the monitor to achieve this.
To connect your Dell UltraSharp U2421HE and U2721DE monitor to your computer:
Dell UltraSharp U2421HE and U2721DE monitor orientation must always be in landscape mode. This includes any wall-mounted monitors and monitors on a stand. In a multiple monitor setup, Dell UltraSharp U2421HE and U2721DE should not be rotated either to 180° (landscape) or 90° (portrait).
When setting up your Dell UltraSharp U2421HE and U2721DE monitor, ensure that the monitor front panel buttons is on the bottom right.
With the stand that is attached to the monitor, you can tilt and swivel the monitor for the most comfortable viewing angle.
When mounted on the wall or on a monitor arm, the set-up must comply with the recommended panel orientation and working angle.
Figure 2: Orientation of Dell UltraSharp U2421HE and U2721DE
Figure 3: Illustration of Dell UltraSharp U2421HE and U2721DE Connection
Use the buttons at the bottom of the monitor to access the On-Screen Display (OSD) menu of the monitor. To access the On-Screen Display (OSD) menu, press Button 3 (Figure 4) at the bottom of the monitor.
Learn more about using the On-Screen Display (OSD) menu. See the Operating Your Monitor section in the User's Guide of Dell UltraSharp U2421HE and U2721DE monitor.
Button | Function | Description |
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Button 1 | Shortcut key: Preset Modes | Use this button to choose from a list of preset color modes. |
Button 2 | Shortcut key for Input Source | Use this button to select the input source. |
Button 3 | Menu | Use this menu button to launch the on-screen display (OSD) and select the OSD menu. |
Button 4 | Exit | Use this menu button to go back to the main menu or exit the OSD main menu. |
Button 5 | Power (with power light indicator) | Use the Power button to turn the monitor On and Off. The white LED indicates that the monitor is On and fully functional. A glowing white LED indicates DPMS Power Save Mode. |
Resetting a monitor to factory defaults can help resolve many video or display issues. To reset your Dell UltraSharp U2421HE and U2721DE monitor to factory default settings, follow these instructions:
Figure 5: Dell UltraSharp U2421HE and U2721DE Front Panel Buttons.
If your Dell monitor has a blank or black screen, fuzzy or blurry image, flickering, distorted, or any other screen abnormalities, running a diagnostic test will help determine if the Dell monitor is functioning normally. Learn How to Run a Diagnostic Test on a Dell Monitor.
It is always essential to isolate the monitor while troubleshooting your computer for the following scenarios:
No Power - Your computer is not powering ON or showing any signs of power.
No POST - Your computer is not showing any indication of activity, the screen might be blank and will not display the Dell logo during start-up.
No Video - You are unable to see any display on the screen, able to hear the windows chime but no display is seen.
Your Dell UltraSharp U2421HE and U2721DE Monitor provides a self-test feature check that allows you to check whether the monitor is functioning properly. If the monitor and computer are properly connected but the monitor screen remains dark, run the monitor self-test by performing the following steps:
Your Dell UltraSharp U2421HE and U2721DE monitor has a built-in diagnostic tool. It helps to determine if the screen abnormality you are experiencing is a problem with the monitor or with the video card on your computer.
When you notice screen abnormalities like distortion, clarity, horizontal or vertical lines, color fade, it is always a good practice to isolate the monitor by running the Built-In Diagnostics.
During the LCD Monitor manufacturing process, it is not uncommon for one or more pixels to become fixed in an unchanging state. Which is hard to see and does not affect the display quality or usability. For more information, see the Dell knowledge-base article Dell Display Pixel Guidelines
This section provides information about troubleshooting steps that can help resolve the most common issues with the Dell UltraSharp U2421HE and U2721DE monitor. Alternatively, learn How to Troubleshoot Display or Video Issues on a Dell Monitor.
Common Problem | What User Experiences | Possible Solution |
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No Video - Power LED Off | No picture |
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No Video - Power LED On | No picture or no brightness. |
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Missing Pixels | LCD screen has spots. |
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Stuck-On/Off Pixels | LCD screen has bright spot. |
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Brightness Problems | Picture too dim or too bright. |
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Safety-Related Issues | Visible signs of smoke or sparks. |
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Intermittent Problems | Monitor malfunctions on and off. |
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Missing Color | The picture does not have color. |
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Wrong Color | Picture color is not good. |
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Image Retention from a Static Image Left on the Monitor for a Long Period | Faint shadow from the static image appears on the screen. |
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Screen image is too small. | Image is centered on the screen but does not fill the entire viewing area. |
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Image Ghosting | Fast-moving images leave a trail of shadow images. | On certain videos and applications with fast-moving images, imaging ghosting, which appears as a trailing shadow, may occur. Change the Response Time to Fast in the Display menu. |
No Input Signal when user controls are pressed. | No picture, the power LED light is white. |
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The picture does not fill the entire screen. | The picture cannot fill the height or width of the screen. |
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Display mode changes from "Second screen only" to "Extended mode" after opening and closing the laptop LCD. | The display mode on your computer reverts to "Duplicate" or "Extend,". This depends on which was selected before you changed to "Second screen only" or "Projector only" when you close and open the laptop screen. When you close and then reopen the lid on a laptop, the Connecting and Configuring Displays (CCD) feature in Windows automatically reverts the display mode to the last active selection. This behavior is by design in Microsoft Windows. |
Switch to the display mode that you want after you close and reopen the laptop screen manually:
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When changing the monitor’s resolution from Windows Display Settings, the image quality may not be good. | Windows Display Settings and the resolution settings on the laptop's video or graphics utility may not be compatible. | Change the resolution using the video or graphics card (GPU) utility like Intel HD Graphics Control Panel. |
No video when the monitor is connected to a Dell docking station. | The monitor may not receive video signals from the computer when connected to a Dell docking station. | To learn more about how to set up and configure the Dell UltraSharp U2421HE and U2721DE monitor with a Dell docking station. See the Dell knowledge-base article How to Connect and Set Up a Docking Station With a Dell Laptop. |
Light leak from the monitor | The monitor appears to have a light leak from the edges in a dark room | This is the normal behavior of the monitor. Dell consumer monitors are inspected at 150-lux ambient lighting (similar to typical office lighting). Dell UltraSharp and Gaming monitors are inspected with tighter criteria of 70-lux ambient lighting (dimly lit room but not dark). |
Color variation on the corners of the monitor | The monitor appears to have a color variation on the corners of the screen | The optimal viewing position for the monitor is from the center of the screen. Dell UltraSharp U2421HE and U2721DE monitor uses a curved IPS panel, the corners of the screen may appear slightly yellowish or pinkish, especially when viewing in the darkroom. This is normal IPS panel behavior and typically does not affect the overall viewing performance.
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Troubleshooting USB Issues | ||
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Specific Symptoms | What User Experiences | Possible Solution |
USB interface is not working. | USB peripherals are not working. |
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THE high-Speed USB 3.0 interface is slow. | High-Speed USB 3.0 peripherals working slowly or not working at all |
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Wireless USB peripherals stop working when a USB 3.0 device is plugged in. | Wireless USB peripherals respond slowly or only work as the distance between the device and the receiver decreases. |
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USB Type-C port does not supply power. | USB peripherals cannot be charged. |
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USB ports on the monitor do not work when the monitor is connected to a computer using USB Type-C. | If the monitor is powered off and then powered on too quickly, the laptop will not recognize the computer. |
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The monitor does not wake up by the USB keyboard or mouse that is connected to the monitor. | In sleep mode, the monitor does not receive power to the USB 3.0 ports. | Wake up the laptop computer using the built-in keyboard or touchpad |
Learn how to view or download the Manuals and Documentation for your Dell Product
Using Windows Display Settings
In Windows 10, Windows 8 or 8.1, and Windows 7:
Using Nvidia Control Panel
To change the resolution using the Nvidia Control Panel:
Using the AMD Catalyst Control Center
To change the resolution using the AMD Catalyst Control Center:
To reset the Dell UltraSharp U2421HE and U2721DE Monitor to factory defaults, see the Reset to Factory Settings section of this article.
The Dell UltraSharp U2421HE and U2721DE monitor has two built-in diagnostics that are available:
Self-Test Feature Check - The self-test feature check on the Dell UltraSharp U2421HE and U2721DE monitor allows you to check whether the monitor is functioning properly.
Built-In Self-Test - The Dell UltraSharp U2421HE and U2721DE monitor has a built-in self-test that helps you identify if the screen abnormality is with the monitor or the video card (GPU) on your computer. When you notice screen abnormalities like distortion, clarity, horizontal or vertical lines, color fade. It is always a good practice to isolate the monitor by running the Built-In Diagnostics.
To learn how to run a diagnostic test, see the Running Diagnostics on Dell UltraSharp U2421HE and U2721DE Monitor section of this Dell knowledge-base article.
The Troubleshooting section of this Dell knowledge-base article provides information about troubleshooting common issues with the Dell UltraSharp U2421HE and U2721DE monitor. The section has troubleshooting steps on how to resolve power issues, video issues, color or clarity issues, distortion issues, horizontal or vertical lines, brightness issues or pixel issues and so on.
To navigate the On-Screen Display (OSD) menu, use the buttons on the monitor. The monitor control buttons are usually on the right side, either on the side, front, or bottom of the monitor. To access the On-Screen Display (OSD) menu, press Button 3 on the monitor.
For more information about using the On-Screen Display (OSD) menu and different menu options. See the Operating Your Monitor section in the User's Guide of your Dell UltraSharp U2421HE and U2721DE monitor.
USB Type-C port on your Dell UltraSharp U2421HE and U2721DE supports USB Power Delivery, Data, and DisplayPort video signal. The USB Type-C port can be used for video and data signal, and supply power (90 W) to a compatible laptop computer using a single USB Type-C cable that is provided with the monitor.
If you are using a Dell laptop computer that supports charging by USB Type-C. It is recommended to update the BIOS and Video or Graphics card (GPU) driver. Learn How to Download and Install Dell Drivers.