Cause #1: A Bad or Loose Display Cable (Most Common)
What's actually happening here is that the link between your GPU and monitor is dropping out. Every cable—HDMI, DisplayPort, DVI—has tiny pins that carry data at high speed. When a cable is loose, bent, or worn, those pins lose contact intermittently. The screen goes black for a second or two, then comes back. It's not random; it's the cable failing under thermal or physical stress.
You'll see this most often after you've moved your desk, swapped GPUs, or run a cable along a heat source like a radiator. The symptom is a flicker that gets worse when you jiggle the cable near the connector.
Fix it in this order
- Reseat both ends. Unplug and firmly reinsert the cable. You want a solid click. If it's DisplayPort, listen for the latch engaging.
- Swap the cable. Don't test the same cable on another port—test a known-good cable. I've fixed dozens of "broken monitors" that were just a $5 cable with a broken pin.
- Check the port itself. If you have a GPU with multiple ports and one is loose, use a different one. On my RTX 3080, the second DisplayPort has always been flaky since day one.
For long runs (over 10 feet), use a thicker cable with proper shielding. Look for VESA-certified DisplayPort cables—they're tested for bandwidth. Don't buy the cheapest one on Amazon; it'll bite you eventually.
Cause #2: GPU Power Delivery or PSU Insufficiency
This one's sneaky. Your monitor doesn't just disappear—the entire display signal cuts because the GPU itself fails momentarily. What's happening is the video card is asking the power supply for more juice than it can deliver under load. The voltage sags, the GPU crashes, and the monitor loses signal.
You'll notice this pattern: the screen goes black during games, 3D rendering, or any GPU-heavy task. It might come back after a few seconds, or you might get a "Display driver stopped responding and has recovered" message in Windows.
The fix
- Use two separate PCIe power cables instead of a daisy-chained one. Most GPUs need 2 or 3 8-pin connectors. If your PSU has a splitter cable, that's a red flag—the single wire can't carry enough current. I've seen this exact issue with a 650W PSU and a 3080; the card drew power through one rail and crashed under load.
- Check your PSU wattage. A 750W unit is fine for most mid-range cards, but a 3090 or 7900 XTX wants 1000W. Use a calculator like OuterVision's PSU calculator. Don't guess.
- Update your GPU driver as a temporary workaround, but don't be surprised if it doesn't solve it. The driver isn't the root cause—it's just the messenger.
If you're on a laptop, the fix is different: make sure you're using the dedicated GPU and not the integrated one. On some laptops, plugging the monitor into the HDMI port routes through the integrated graphics, which can't handle higher refresh rates. I hit this on a Lenovo Legion 5—the HDMI port was wired to the iGPU, and I had to use USB-C with DisplayPort to get a stable signal.
Cause #3: HDMI/DisplayPort Handshake or EDID Confusion
Here's the scenario: you turn on your PC, the monitor wakes from sleep, and then it cycles through inputs—HDMI 1, HDMI 2, DisplayPort—before giving up and showing "No Signal." Or the screen goes black when you switch inputs. This is a handshake problem. The GPU and monitor negotiate a resolution and refresh rate over the cable. If that negotiation fails, both sides sit there confused.
This happens a lot with older monitors or when you have multiple displays with mixed refresh rates. The EDID (the monitor's profile) gets misread, and the GPU sends a signal the monitor can't display.
Fix it
- Turn everything off, then on. Fully shut down both the monitor and the PC. Unplug the monitor's power for 30 seconds. Then plug it back in and power on. This resets the EDID handshake—it's the oldest trick in the book but it works more often than you'd think.
- Change the refresh rate in your OS. If you're running 144Hz, drop to 120Hz temporarily. If the signal holds, the monitor or cable can't sustain the higher rate. On Windows, go to Settings > System > Display > Advanced display settings. Set it to 60Hz and test. Then work your way back up.
- Disable Deep Sleep on the monitor. Some monitors (especially Samsung and LG) have a power-saving feature that kills the signal after a few minutes. Look for "Deep Sleep," "Power Saving," or "Eco Mode" in the OSD and turn it off. This alone fixed a friend's LG 27GL850 that went black after 10 minutes every time.
Quick-Reference Summary Table
| Symptom Pattern | Most Likely Cause | First Fix to Try |
|---|---|---|
| Flickers when cable is moved | Loose or damaged cable | Reseat or replace the cable |
| Black screen only under heavy load | GPU power delivery / PSU | Use separate PCIe power cables |
| Black screen after sleep or input switch | Handshake / EDID issue | Power-cycle both devices, disable Deep Sleep |
| Signal drops then comes back with driver warning | GPU crash due to power or thermals | Check PSU wattage and GPU temps |
If none of these fix it, test the monitor on another PC. If that works, your monitor is fine—the problem is in your system, and you've ruled out the easy causes. If it still drops on a different PC, the monitor's internal board is failing. At that point, it might be cheaper to buy a new monitor than pay for repair.