Since upgrading my GPU and CPU and updating the BIOS, my secondary monitors sometimes go black for a few seconds and reconnect. The main display stays on, and games and audio keep running. It often happens when launching apps or changing display settings.
The same problem now happens with my old GPU too. Each secondary monitor can do it on its own, and I've tried another monitor, different HDMI cables and clean driver installs. What should I check next?
Since both GPUs show the issue now, look at what they share rather than assuming the new card is faulty. The motherboard, power connections and display cabling are all worth checking, especially since the case was opened during the upgrade.
Shut the PC down, switch off and unplug the power supply, then check that the 24-pin motherboard connector and GPU power connectors are fully seated. Reseat the graphics card too, and check that its display cables are firmly plugged in. Don't open the power supply itself.
A loose connection doesn't have to cause this exact symptom, so consider it a check rather than a diagnosis. If nothing changes, move on to testing the display signal paths.
I'd isolate the signal path one piece at a time. Connect just one affected monitor, then try a different GPU output and a direct cable if the monitor supports one. For the DisplayPort to HDMI screen, swap the adapter as well as the HDMI cable, or try a direct DisplayPort connection if available.
Keep the refresh rate and other settings unchanged while swapping parts. Then try the other secondary monitor the same way. That may show whether a particular port, cable or adapter is involved, though it won't necessarily explain why both displays can drop.
The timing around launching apps and changing refresh rates makes display mode changes worth testing. With one secondary connected, try matching its refresh rate to a supported rate on the main monitor, then launch the same apps that tend to trigger the blackout. Also try running a game in a window instead of exclusive fullscreen.
Note which combination triggers it and whether Windows makes a disconnect sound or rearranges windows. A brief mode change can blank a display, but that doesn't prove it's the cause here.
Don't overlook the BIOS update as another change in the mix. Check the current display-related settings and motherboard documentation before changing anything. If you experiment with BIOS settings, record the existing values first and make sure your backups are current. That gives you a way back without guessing what was changed.
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d614-latchkey:
Could a loose power connection cause just the secondary displays to drop without the PC crashing?
5j+notchcase_728:
It's possible, but the symptom alone doesn't establish that power is the cause. The fact that the main display stays up makes the individual display connections worth checking too.