Hi jimyhunt,

Since you have mentioned that screen flickers intermittently, you can run the LCD BIST test in the system to check the LCD is working as designed. Follow the steps below.

Turn the computer off >restart the computer

 At the Dell logo screen, start tapping the F12 key a few times until you see the ‘One Time Boot Menu’ appear.

 At the one time boot menu press the down arrow key to highlight ‘Diagnostic’, then press Enter to begin the PSA diagnostics.

You will soon see different colors on the screen; at this point please press ‘N’ which will begin the LCD BIST Test. This test will help us to identify, if there is any issues with the LCD.

The screen will display multiple flashing colors. If you observe any blurry video, distortion and or any lines on your screen, we are not looking whether the test is passed or failed. Please check the LCD flickers during the test.

Please do reply for further assistance.         

Thanks for the reply.

I have tried the above suggestion, and I did not see anything out of the ordinary.

My screen hasn't flickered for a few days now. But this is normal for it. Some days are good somedays it decides to flicker.

Hi jimyhunt,

Since the flickering is intermittent, I request you to connect an external monitor and check if the display flickers on the external monitor.

You may also check in the BIOS screen. To go to BIOS restart the system and at the Dell logo tap the F2 key every two seconds. Leave the system in the BIOS screen for a while as the issue is intermittent to check if the screen flickers.

Reply with the status for further assistance.

I was working on the laptop today and the screen started to flicker.

I connected a external monitor (my TV) via HMDI.

The TV did not flicker at all. The LCD on the laptop kept flickering.

Other things I noticed:

Moving the mouse pointer was not smooth and seemed to judder and jump on the TV screen.

Every 10 -15 seconds if the mouse pointer was not moved the TV screen would go black and then come back on. When it did the mouse pointer was in the middle of the screen.

I then restarted the laptop and went into the BIOS with the TV still connected via the HDMI. It did not flicker after the reboot in the BIOS or when it booted back into windows. But I have seen it stop flickering as quickly as it starts

I will try it again, when it starts to flicker I will get it into the BIOS screen. I will report back with the findings...

Hi jimyhunt,

In case the issue repeats, I request you to reply to this post or start a new thread for further assistance.

Okay, it started to flicker again today. I went into the bios and it continued.

I tried it on battery and just mains power. This did not fix it.

I reconnected the back light for the keyboard. This did not fix it either.

I did notice that the keyboard back light flickered with the screen back light.

I left it powered for an hour or so. I came back it had stopped.

Anybody else had this problem?

I am having the exact same problem.. I have checked cable connections and it did not help.. I suspect the problem is with the area that supplies power to light the screen and the keyboard back light.. I am guessing it is a mother board issue, but I don't know how to prove it.. I am going to try and disassemble far enough to get some freeze spray on the motherboard while the flashing is happening... Any other ideas would be great...

This EXACT same problem started on our 1749 yesterday.  Between screen flashes, we can type in our Windows login password and initially get to the Windows desktop.  But within a few seconds, the lights above the keyboard sequence to the left and then to the right, and then we are returned to the Windows "Locked" screen.

Hi peterkap,

Please connect an external monitor and check if the screen flickers, also run the hardware diagnostics to check if the hardware is working as designed. Start tapping the F12 key a few times during startup until you see the ‘One Time Boot Menu’ appear.

At the one time boot menu, press the down arrow key to highlight ‘Diagnostic’, and then press Enter to begin the hardware diagnostics.

If the test fails, please make a note of any error codes listed. You can also refer to the link below.

http://dell.to/OUGnqT

let us know about the progress.

Thanks for the quick response yesterday, Senthil.  I took the 1749 downstairs to our basement (where it is cooler) and removed the battery.  Later that evening, I installed the battery, powered on the laptop and it's been working ever since. I ran the diagnostics like you suggested, as well as the long memory test and the Extended System Tests.  No failures.  As a side note, earlier this year the laptop shut down, I believe, due to overheating.  The left side under the keyboard had gotten very hot.  Ever since then, we've been using a Tagus Cooler, AWE80US.  This flickering/locking is the first failure since that time.