boots to black screen but external monitor fine, voltage on the adapteris correct

[tangerine51]

boots to black screen but works with external monitor.  can't get into bios.  ran HP PC Hardware Diagnostics Windows 2.7.2.0. video memory passed.

computer works perfectly on external

white light flashing intermittently in back of PC above power jack.

shined a flashlight, no faint image on screen

boots to black internal display

[Garp_senchau]

@tangerine51, Welcome to HP Support Community,

Thank you for posting your query; I’m here to help by guiding you through steps to resolve this issue

Display duplicated

Verify whether the display is duplicated, then try switching it to your screen instead of duplocating or extending it.

Press Win+P to see if the screen is only on the second screen.

Try a BIOS Reset via Key Combination

Since BIOS doesn’t show on the internal display:

Power off the PC completely

Hold Windows + B

While holding, press and hold the Power button for 3–5 seconds

Release both and wait ~30 seconds

This forces a BIOS recovery/reset on HP machines. If it works, the internal display might flash or restore.

Reference: HP Notebook PCs - Recovering the BIOS (Basic Input Output System) | HP® Support

Hard Reset the Hardware

Unplug power cord

Hold the power button for 15 seconds

Plug it back in and turn it on

Sometimes a residual charge can confuse internal video detection.

Check Device Manager

Expand Display Adapters

Expand Monitors

If the internal monitor is not listed, it may be a hardware or cable failure.

Boot into UEFI via Windows

You can try entering BIOS/UEFI another way:

Go to Settings → System → Recovery → Advanced Startup → Restart Now

Choose UEFI Firmware Settings → Restart

See if this forces the BIOS to appear on the internal.

I hope this helps.

Please feel free to reply here if you have any questions or if you need further clarification on any of the steps. 

Take care and have a good day. 

Did we resolve the issue? If yes, please consider marking this post as "Accepted Solution" and click "Yes" to give us a helpful vote - your feedback keeps us going!

Regards,

[tangerine51]

Thank you so much.  I tried all of this with no success except anything to do with bios .

bios is from 2023, well confirmed with cpu-z third party utility.

i tried safe mode it was a disaster ended up taking out hdd to another machine , decrypted , ran bcd (scary) to turn off safe mode bit.

internal display appears in devmgmt and says aio monitor (not generic monitor)but driver is generic from like 2006 and when I tried to update it said already the latest.

in windows display utility it also knows there are two monitors.

glows a bit, flashlight test shows absolutely no faint image.

i have part no of lcd ready to order, lvds cable replacement arrives Thursday (crossy fingers!)

don’t want to do anything with bios afraid it will make things worse. Can’t afford for external to stop working again.

voltage on barrel of adapter fine in no load. Don’t know how to test it on load, don’t know how to check wattage.  Research is telling me if voltage on barrel of adapter is fine then the adapter is fine. No other symptoms related to a voltage sag so am ruling out adapter.

the lcd is expensive I wish I could test lvds socket on board but i do not have oscilloscope or knowledge of how to use and the pins of lvds are fine pitch looks too difficult for me. 

thanks, this is a high spec all in one.

[tangerine51]

Re

Go to Settings → System → Recovery → Advanced Startup → Restart Now

Choose UEFI Firmware Settings → Restart

there was no option choose UEFI firmware settings when I followed that path (tried twice).

also tried press and hold power button to drain capacitors to no avail.

did not try updating or resetting bios. That kind of thing has never helped me and I really am afraid it will make things worse.

[Hawks_Eye]

@tangerine51 

It sounds like you've gone through an extensive troubleshooting process, and I completely understand your hesitation about making BIOS changes—especially since your external monitor is still working. Given that your LVDS cable replacement is arriving soon, that might be the best next step to test before considering anything more drastic.

Your research on the adapter voltage makes sense—if there’s no sag and no other symptoms, it’s likely fine. Testing LVDS socket connectivity without an oscilloscope is tricky, but if the new cable doesn’t resolve the issue, you might consider checking for physical damage on the connector itself.

Fingers crossed for Thursday! 

Let me know how it goes, and I’ll be happy to help if you need further guidance.

Regards,

Hawks_Eye

[tangerine51]

Really appreciate the support. Can’t wait to try the new cable!

[Hawks_Eye]

@tangerine51 

Glad to hear it! Hope the new cable does the trick—sometimes it’s the simplest swaps that make all the difference. 

Keep me posted on how it goes, and if you hit any snags, I’m here to help. Fingers crossed for a smooth fix!

Regards,

Hawks_Eye