Laptop black screen after cleaning

[Sipno]

Hey guys, I have an HP Dv7-2030ev.
I opened the fan to clean it and changed the thermal paste.
I followed the steps as they've been showed here:
https/www.youtube.com/watch?v=Txx6Y7XkKw8
After that I had a black screen.
The first time I had assembled the laptop I supposed that the heatsink wouldn't have fit correctly, so I reopened it and checked it, but for a second time I had a black screen.
I tried to be pretty accurate in order not to spoil any connector, as it wasn't my first time as I have cleaned a laptop.
I hadn't any beeps after I pushed the ON button,even I removed memory or the hard drive.
All the lights were blinking correctly, but I had no response If I pushed caps lock for on/off state.

Any ideas?
Thanks in advance

 

[Laptop_Nerd]

Hi,

Something inside might have been disconnected or was loose after you opened. Have you tried checking the ribbon cable that connects the LCD to the motherboard? Here are some troubleshooting steps that may help.
- Start by doing a hard reboot, remove the battery and unplug the AC adapter then press and hold the power button for 20 seconds then try booting it up again.
- If this will not work, do test the AC adapter if it's working properly. Remove the battery and power the laptop with just the AC adapter connected and see if it will boot up or not. do also try a different AC adapter that has the same voltage and see if it will work or not.
- Proceed with reseating the RAM's if trying a different AC adapter will not work, remove them all for couple of seconds then put them back in making sure everything is seated properly.
- If it will still not work, connect an external monitor and see if you'll get any display from it. If there's a display on the external monitor that could mean that the problem is the built in display.
- But if there's still no display on the external monitor that means the problem lies in the motherboard.

 

[Sipno]

After trying to hard reboot, the hard reboot is not working. I pressed for 20 sec the button and it didn't go off. It doesn't go off after pressing the button, only ON state.
I tried also reseting the rams and removing the hard drive in order to check for any beep, but nothing.
I tried to connect it with other screen, I had no signal.

 

[Sipno]

Hi,

Something inside might have been disconnected or was loose after you opened. Have you tried checking the ribbon cable that connects the LCD to the motherboard? Here are some troubleshooting steps that may help.
- Start by doing a hard reboot, remove the battery and unplug the AC adapter then press and hold the power button for 20 seconds then try booting it up again.
- If this will not work, do test the AC adapter if it's working properly. Remove the battery and power the laptop with just the AC adapter connected and see if it will boot up or not. do also try a different AC adapter that has the same voltage and see if it will work or not.
- Proceed with reseating the RAM's if trying a different AC adapter will not work, remove them all for couple of seconds then put them back in making sure everything is seated properly.
- If it will still not work, connect an external monitor and see if you'll get any display from it. If there's a display on the external monitor that could mean that the problem is the built in display.
- But if there's still no display on the external monitor that means the problem lies in the motherboard.

After trying to hard reboot, the hard reboot is not working. I pressed for 20 sec the button and it didn't go off. It doesn't go off after pressing the button, only ON state.
I tried also reseting the rams and removing the hard drive in order to check for any beep, but nothing.
I tried to connect it with other screen, I had no signal.

 

[Sipno]

Anyone else?