Hi @ds_1 ,
Things to try:
a. Try entering BIOS on startup and check if the problem is still there. Press F10 on startup when (if?) the HP logo appears. This is to determine if it is an OS software problem or a hardware problem.[br]
b. ''If it doesn’t occur when in the BIOS menus'' then try starting the laptop in [https://www.digitalcitizen.life/4-ways-boot-safe-mode-windows-10/|safe mode] and check if it happens.
''If it doesn’t happen when in safe mode'' then there is a driver problem. Check that the display adapter drivers in Device Manager are up to date and that it is installed correctly
c. ''C''onnect an external monitor to the laptop and check if the problem occurs on it or not. Press F1 to toggle between the displays i.e. laptop only, both displays on together, extended display or external display only
''If the problem is still there on the laptop screen only,'' then most likely it is a screen hardware problem, display cable or LCD panel.
''If the problem occurs on the external monitor also'' it is a GPU or motherboard problem
''If you determine that the problem is with the LCD panel'', here’s the [http://h10032.www1.hp.com/ctg/Manual/c06200645|maintenance and service guide] for the laptop. Go to p.24 (non touch screen Item #4) or p.25 (touch screen model Item #1) to find the part numbers for the LCD panel. Search online by typing the appropriate to your model part number ''only,'' in the search box of your browser to find suppliers that suit you. Usually the part number can be found on the back of the LCD panel somewhere, if you wish to verify that you’re ordering the correct part.
The manual also details the necessary pre-requisite steps and then the procedure to remove/replace the panel.