Three checks before opening anything
The monitor’s own input button
Monitors have multiple inputs and a mind of their own about which to show. Press the Input/Source button on the monitor and cycle through — the wrong input is the single most common “dead” monitor.
Reseat — and mistrust — the cable
DisplayPort plugs have a latch that can look and feel seated while half-in. Unplug both ends fully, reconnect firmly, and if there is any spare cable in the house, swap it — then try a different port on both monitor and computer.
Cross-test with a laptop
Any laptop into the monitor: picture appears = monitor and cable are innocent, the desktop is the suspect. No picture = you just saved yourself from debugging a healthy computer.
Plugged into the wrong ports on the back
If the desktop has a graphics card, the monitor must plug into the graphics card’s ports — the horizontal ones lower on the case — not the motherboard’s ports up near the USB cluster. The manufacturers say it themselves: motherboard video outputs are dead unless the processor has built-in graphics, and many desktop chips (most gaming Ryzens, Intel “F” models) simply don’t.
This bites hardest after moving a PC or rebuilding a desk — everything gets replugged, the cable finds the top ports because they are easier to reach, and a perfectly healthy computer boots into a black screen. It is the first thing we check on every “dead PC” call, and it is free.
When the easy three don’t do it
Wakes-from-sleep blackouts: a widely reported DisplayPort quirk — the link drops during sleep and never renegotiates. Power-cycle the monitor with its own button; if it recurs, look for a “deep sleep” toggle in the monitor’s menu to disable, and update the graphics driver. PC powers on but never beeps/posts: fans spin, screen dark, no logo — that is the computer failing to boot, not the monitor; vendors’ own flowcharts start with reseating the RAM sticks. At that point you are inside the case — a fine moment to stop and call, because the next steps (one stick at a time, clearing CMOS) are where confident guessing starts costing money.
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Bring it to the people who do this daily
No shame in it — some faults are hardware, and some setups fight back. Call or text us a photo of the setup and we will tell you in one minute whether it is a five-minute fix or worth a visit.
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More guides: Laptop running slow · Printer offline · Our computer repair service
Quick answers
The monitor says 'No Signal' then goes to sleep instantly.
The monitor is fine — it is announcing that nothing is arriving. Input button first, then cable, then the right-ports check. 'No Signal' on screen actually proves the monitor's panel works.
It works at the desktop but goes black in games.
Different problem — the game is requesting a resolution/refresh the link can't hold. Cap the game's refresh to the monitor's real spec, and on high-refresh monitors use the cable the monitor shipped with, not a drawer cable.
Second monitor detected but black?
Windows key + P chooses the multi-monitor mode — 'PC screen only' blanks the second display on purpose. Pick Extend, then check Settings > Display for the layout.
HDMI or DisplayPort — does it matter?
For office work, either. For high refresh gaming monitors, DisplayPort generally carries the top modes. What matters more: one good cable, fully seated, rated for the resolution you run.