Now I know how to 'artificially' remove the problem and how to make it re-appear, which is good for testing purposes. However, shutting down the computer and booting it a second later does make the problem re-appear. Restarting the computer after the above is done, does not make the problem re-appear. Shutting down the computer, removing the battery, putting it back in a second later and booting 'fixes' the issue for the time being. So I kept on trying and figured out the following. I am too fond of my Samsung display so I wouldn't give up after you explained to me that I basically could end up with any of the other displays if I issued a repair. I guess I should use my warranty to get my T420s fixed since I without doubt think this is a hardware issue. Then I would never be able to use sleep mode. I cannot remove the battery each night only to reseat it the next morning.
removing the battery and waiting 5 minutes fixes the issue as it did before. However, as I booted my Thinkpad the next morning, it was back. I thought I had fixed it! I checked the Device manager several times that day and there was no ghost display visible. Sure enough when I booted up the 'Generic non-PNP Display' was gone! I unplugged the power cord to my Thinkpad, removed the battery and waited 10 minutes. I was desperate for a solution to my problem and so I figured I'd try something as similiar to this.
This was a thread about a similiar problem for a desktop and it was suggested that the person in the thread should disconnect his LCD from the PC and unplugg the powercords and let it rest for 5-10 min. Lastly I heard it could be due to electricity caught up in one of the capacitators that the output used (or something like that). For this I need to send it in to get it fixed, but I did not give up yet. I also read it could be due to electrical load on the port due to a faulty graphics unit. I read that this non-PNP phenomenon could be due to dust in the VGA. Then when I plug in an external display it finds a display on that same port, replacing the non-PNP display status. As such it cannot detect which display it is i.e. This would probably suggest that the hardware thinks theres a display connected when there isn't. I figured that there was something wrong with VGA port or one of the GPUs. I plugged in my external display to the VGA and as I did so it replaced the non-PNP with PNP. Then I started to look at the hardware side of things.
I tried uninstaling drivers, then installing the video drivers from Intel and Nvidia support sites. I started to uninstall drivers then reinstalling drivers. I started to look around on the web for solutions as I wanted to bring this to an end asap. I figured this was because the Thinkpad thought there was a secondary display and sure enough the Device Manager and the screen-res settings in windows showed a 'Generic non-PNP Display'. If I let the computer enter sleep mode by itself (due to inactivity) and then woke it up, the built in display would be turned off and I had to use Fn+F7 and kind of work my way, blindly, to the right display output. Related Product Picture Mfg.Before I start talking about the problem I have Thinkpad T420s 4173-W1J (which has Intel HD + NVS4200) and I have never used it with any external displays prior to this issue:Ī while ago I noticed a strange problem.