How to check a monitor after a power surge

After a power surge, your monitor may look normal, flicker, show lines or colored patches, or stay blank. The same symptoms can come from a damaged cable, computer, graphics output, or power strip, so test the display in a safe order before deciding what needs repair.

Start with a visual check for electrical damage. If you notice smoke, a burning smell, crackling, scorch marks, or unusual heat, do not power the monitor on to test it. Disconnect it from power if you can do so safely, and arrange a repair or replacement.

Check the monitor

Once you have confirmed there are no signs of electrical damage, turn on the monitor and open the Display Test. The test checks pixels, colors, and refresh rate in your browser.
Use the color checks to inspect the whole screen. Look for a pixel that stays black, white, or a different color from the surrounding area, as well as patches, lines, or uneven areas that remain visible across different colors.
Watch the screen for flicker, brief blackouts, flashing lines, or changes in brightness. If the problem appears only when the computer is connected, note when it happens and whether it changes as you move the cable gently at its connectors.
Check the refresh rate shown by the test. Compare it with the rate you normally use, but remember that the computer's display setting and the connected cable can affect what the browser reports.
If the picture is abnormal, try a different video cable or input, then test the monitor with another computer or video source if one is available. Change one thing at a time so you can tell which part changes the result.

Do not open the monitor or remove its casing. Internal parts can retain dangerous voltage even after the power cord is unplugged.

What the result means

The colors look even and the pixels look normal

The panel appears to display the browser test correctly at that moment. This is reassuring, but it does not prove that the monitor's power circuitry is undamaged or that an intermittent fault will not return. If the computer still loses the picture, check the cable, graphics output, and computer next.

A dot stays the wrong color on every test

A single pixel that remains black, bright, or colored while the surrounding screen changes may be a stuck or dead pixel. A single pixel does not by itself prove the surge caused it. Compare it with the monitor off and on, and see how to check a monitor for dead pixels for more ways to distinguish a pixel fault from an image or software issue.

Lines, blocks, or flicker appear across the screen

If the defect appears over the browser test and the monitor's own menus, the monitor or its power supply is a stronger suspect. If it disappears when you change the cable, port, or computer, the original signal path is more likely to be involved. A browser test cannot identify which electronic component failed.

The screen is blank or says there is no signal

The monitor is not showing the computer's picture, but the panel may still be working. Check that the monitor is on the correct input and that the cable is fully seated. If its own menu appears, that confirms the panel can display at least that menu, not that the computer is sending a usable signal.

The refresh rate is lower than expected

A lower value can result from the computer's display settings, a cable or adapter, or a limit on the connected port. It is not proof of surge damage. Check the selected resolution and refresh rate in your operating system before treating the reading as a hardware fault.

How to fix the problem

Check for electrical warning signs. If you see smoke, smell burning, hear crackling, or feel unusual heat, unplug the monitor only if you can do that safely. Do not keep switching it on to see whether it recovers.
Reseat the power and video cables. Turn the monitor off first, then check that each connector is firmly attached and that the cable has no visible damage. If you suspect the power cord or surge protector was affected, do not keep using it.
Select the correct monitor input. Use the monitor's own input control to choose the port connected to the computer. If you have another compatible video cable or port, test it separately.
Check the display settings. In Windows 11, open Settings › System › Display › Advanced display and check the selected display, resolution, and refresh rate. On a Mac, open System Settings › Displays and review the display options. Choose a supported setting if the current one is not available or looks incorrect.
Compare with another source. Connect the monitor to another computer or a compatible device, or connect the original computer to a known-working display. If the fault follows the monitor, the monitor or its power connection is more likely. If it follows the computer, investigate its graphics output or settings.
Restart only after checking the equipment. If there are no signs of electrical damage and the cables are sound, turn the computer and monitor off, wait about a minute, then turn them on again. A restart can clear a temporary display handshake problem, but it will not repair damaged hardware.

If the issue began after changing a video cable, use these checks for a display after an HDMI cable change to help separate a cable or connection problem from a panel fault.

When the monitor may need repair

A monitor is more likely to need service if it repeatedly flickers or shuts off with different cables and different video sources, or if its own menu shows lines, discoloration, or patches. A monitor that will not power on after a surge may have a failed power supply, but a browser test cannot confirm that diagnosis.

Check the manufacturer's warranty and contact its support service before arranging a repair. Do not open the casing or attempt an internal power supply repair. If the repair costs approach the price of a replacement, replacing the monitor may be the more practical option.

What this browser test cannot check

The Display Test shows images in the browser, so it can help you spot visible screen defects and view the reported refresh rate. It cannot test the monitor's electrical safety, inspect its internal components, or prove that it will remain stable during longer use. It also cannot tell whether a surge damaged the computer's graphics hardware instead of the monitor.

If the monitor passes the test but the original problem returns, note whether it happens with a different cable and source before contacting support. That comparison gives a repair technician a more useful starting point.