nvidia - ubuntu 18.04 Black screen after login

In ubuntu 18.04 after discovering that the wrong nvidia driver was polluting my kernel.log I've tried different combination of nvidia drivers with no success.

When I sudo service gdm start the login screen shows up but after login a black page blocks everithing,

4.15.0-33-generic

nvidia-340:
  Installed: 340.106-0ubuntu3
  Candidate: 340.107-0ubuntu0~gpu18.04.1
  Version table:
     340.107-0ubuntu0~gpu18.04.1 500

        500 http://ppa.launchpad.net/graphics-drivers/ppa/ubuntu bionic/main amd64 Packages
 *** 340.106-0ubuntu3 500
        500 mirror://mirrors.ubuntu.com/mirrors.txt bionic/restricted amd64 Packages
        100 /var/lib/dpkg/status

How can i diagnose/solve this?

UPDATE:

Same problem with a fresh install after installing nvidia recomended drivers.
Resolved avoiding nvidia drivers.

Should this be a hardware error?

Btw video card runs with no problem in Windows.

I had same problem with both Ubuntu 18.10 and 19.04. I have a dell Vostro 3670 (see https://linux-hardware.org/?probe=0f87997cd1). This solution did not work for me. After reboot the screen stays blanc. I found a solution to restore the Ubuntu desktop at least. From #17 on proprietary drivers not showing up - Page 2

I found several proposed solutions for this issue to install the
Nvidia drivers. None of them work for me. I found 2 methods that
enable you to recover the Desktop environment when this happens:

First by Fossfreedom at -
https://discourse.ubuntubudgie.org/t/nvidia-390-black-screen/97/14

You have to do a safe boot and go to root, then:

sudo apt-get remove nvidia-*

sudo apt install nvidia-prime
sudo prime-select intel

Then reboot.

Second form sgian entry #3 at
https://ubuntuforums.org/showthread.php?t=2399985

Also do a safe boot and go to root. Then:

sudo apt purge nvidia*
sudo apt install --reinstall xorg xserver-xorg-core

Then reboot.