I recently changed my hp x360 lcd. the replacement LCD shows the hp logo and goes upto the startup screen where i could enter the user password. as soon as i enter the password the screen starts to flash white continuously. i thought its faulty screen and used a screen from another vendor. but it still does the same thing i could see the hp logo and it starts flashing as soon as i input the password. the screens starts to flash when i go to bios too. i connected to an external monitor and it works fine as i could login and use on the external monitor. after trying for a while the screen does does not show anything now, its just black but when connected to external monitor it shows display. can someone help me out with this issue because i have changed two screens from different vendors.
So you say you replaced the display, and the new one still does this?
It could be the cable that connects the display to the motherboard. If it is damaged, loose, pinched, etc., that can cause issues. I would start there.
If replacing that doesn't resolve it, then I have to ask are you sure that the new display is actually the right one? If you got an alternate (and not the exact same one) or you got a damaged one, that could cause this.
The fact that it is working on an external display shows that it isn't the graphics card.