Dell Inspiron N5110 dark screen after HDD replacement

I am working on a Dell Inspiron N5110 laptop. The computer had a failing hard drive so I dissasembled it and replaced the hard drive. Note that with this model the entire laptop has to be taken apart. The motherboard has to be removed and turned over to where the hard drive is mounted directly to the motherboard.

I originally wrote the following notes that are in italics just to keep my thoughts straight. Then afterwards I discovered that this screen uses an LED backlight.

I replaced the hard drive and found that the screen is now dark. Please also note that I am very careful about static and use all the safety equipment to prevent any damage it may cause. I can direct the video to a remote monitor and everything is fine. The dark screen acts as if the backlight has gone bad or possibly the inverter. You can use a flashlight and see the images on the screen. One thing to note is that I then restored a factory install to the hard drive so that I could run some of the diagnostics that come with the laptop. For instance if you hold down the D key while pressing the power button it goes directly into a video test. The beginning of the test is dark, but when it gets to the color screen tests, such as green, blue, etc. the screen lights up as if nothing was wrong with it. This only lasts until the system is restarted.

I have googled several sites discussing this problem, a few of which stated that all they did was replace the hard drive and had the same thing happen to them. They did not mention whether or not they could get the screen to light up during the test as I did. A couple of people mentioned that their computer was still under warranty; and that Dell replaced the screen and the motherboard before they could get it to work. One replaced the screen with no results. Another person stated that he worked on several of these and the connector where the monitor cable plugs into the motherboard does not have a good connection. I checked and rechecked that connection and even went so far as to replace the video cable. (I did that before I could get the screen to light up under test). Since the screen lights up under test, it appears that the connections are good.

One very important thing to note with this model is that this computer has no separate inverter board; it is built into the screen. I have never worked on a monitor problem whose screen is designed quite like this one.

It seems strange that by just opening the laptop and replacing the hard drive one could cause such problems, unless it was just a connection. A change in hard drive alone should make no difference unless something is designed to cause such a problem whenever a hard drive is replaced. (Just a possible conspiracy theory ).

One theory that I have is that the high voltage required to overcome the initial resistance of the CCFL light is not being achieved until the Dell diagnostics is run; once enough voltage has overcome this, the CCFL lights, and once it lights it no longer requires the high voltage to remain lit and maintain the currrent required to do so. It is my understanding from what I have read that the LCD BIST test runs independent of the video controller. There may be something in that, though I haven't quite put my finger on it yet. Somehow the test must ramp up more voltage than during normal start up. Though all this may be true, it still doesn't answer why this just happens once the hard drive has been replaced. NOTE: There were no issues like this prior to opening the laptop.

Another possibility that came to me is that the power required to run the new hard drive is more than the old one and somehow is enough to prevent the CCFL light from lighting. By this I mean that it may have more of a power drain on the system so that it doesn't leave enough to fire the light. I replaced a Western Digital Scorpio Blue model WD6400BPVT-75HXZT1 with a Western Digital Scorpio Black model WD5000BPKT. The Blue (original drive) uses uses 1.6 Watts read/write average usage (0.95 amps peak usage), and the Black (new drive) 1.75 Watts read\write average usage (1.15 amps peak usage). Is that really enough difference in power usage to expose the systems deficiencies?

I installed the original drive to test this possibility and still nothing...

I can press F12 during bootup and I get the option to run the full Dell tests. When I run the full screen tests without acknowledging I can see the test patterns or not the screen lights up and stays lit until I shut the computer down. So the backlight does function. What am I missing here?

I would appreciate any help I can get with this problem.

 

<SOLVED> I Had this problem with a clients computer yesterday. The (western digital 500gb) hard drive was failing so I replaced it with an hgst. Cloned the drives.
An hour or so later the screen suddenly went dim by 50% or more. I thought the screen was going to sleep, but when I moved the mouse and tried FN-Brightness adjustment, nothing happened.

I rebooted and noticed that the screen would dim after the mouse cursor popped up on the screen. This happened every time I rebooted. This made me believe it was a driver, or software driven dimming.
Also, initially the screen would not dim in Safe Mode, but later after a few reboots it just stayed dim, and no longer was bright before the cursor emerged.

Tested the fuse next to the video ribbon cable and it was okay. Checked the ribbon cable connection on both sides. Ok.
I searched through online threads which mostly described this issue arising after HDD change-outs.

So I decided to change the hard drive again but with the same brand (western digital) as the original drive and BAM! fixed. No more dim screen.
Clean install this time.

The Dell N5110 Motherboard must have a glitch with certain hard drives, or hard drive voltages. Try changing the hard drive out before attempting to install a new motherboard.