Changing the backlight of an Inspiron 9300 LCD panel


How difficult can this be?  I later learned this activity has a geek score of 8.0 and the answer to the question is “more than you’d want it to be”.  The old adage has it that a little bit of knowledge can be a dangerous thing and I got caught.  The screen on my Inspiron 9300 is massive 1900 x 1440.  It’s great.  But recently it began to fade making it increasingly difficult to read in ambient office light.  I read about the potential reasons for fading light, one of which is a backlight coming to the end of its life.  The diagrams on various web sites made it look relatively straight forward and $15 for a new lamp vs $250 for a new panel made it seem like changing the lamp would be worth a go.  So I ordered a new lamp (MSLDELL17W) from www.lcdparts.net which came in a few days and set about installing it.

The instructions for getting the LCD panel out are on the Dell web site and clearly show how to remove the bezel (the bit of plastic around the display), take out the display and disconnect it from the base. Easy (really!). But that was where easy ended. With hindsight, I should have realized that the process was going to be difficult when the lamps (I ordered a spare – and good job too) didn’t look like I expected. The light is evenly displayed over the whole display so my mental image was of one big or a few smaller lamps that pretty much covered the entire area. What arrived was a pair of white sticks each not much bigger than strands of spagetti about the same length as the width of the screen. I thought they’d got the order wrong.

I also thought that I’d see the lamp when the panel was removed from the laptop lid, that it would be in some compartment with a lid held on by some small screws. Nope. Completely wrong. To my credit when the realization dawned that the panel assembly would need to be taken apart somehow, I proceeded very slowly and carefully. Mind you, the area on the back covered in plastic with DO NOT TOUCH written all over in big red letters engendered a mood of caution. After an hour of patient work the panel was in pieces, or at least open and amenable to repair. The inverter was disconnected and removed, the plastic adhesive areas had been peeled away from the frame and the display panel itself taken out of its frame by carefully easing the small lugs on the panel from the corresponding holes in the frame.

To my horror the lamp was still nowhere to be seen. Oh, well, can’t stop now. There was only one place it could be. It turns out that a panel is a collection of layers. The LCD display is etched (or maybe stuck) onto the back of the glass panel that forms the screen you see. Behind this are several translucent plastic sheets, then another glass panel and finally a stiff white plastic backing sheet which forms the back of the panel. Along one edge of this sheet (the same edge to which the inverter is attached) is a thicker white plastic thing. After lots of um-ing and arr-ing it became clear that the only place to put the spaghetti-like lamp was behind this plastic strip and after more prodding and poking it became clear that the plastic backing with its attached strip would slide out of the panel revealing a translucent and polarized glass panel.

So far, awkward but solid progess but it was at this point things started to go wrong. For a start, the sites I visited indicated that the power to the lamps would be provided by wires attached by unpluggable caps. No, they’re soldered on. This dawning awareness occurred when the original lamp snapped (they’re also as brittle as spaghetti) as I tried to remove the caps. OK, no going back now. On the positive side, it made it much easier get the old lamp out and see how it all fit together.

With the backing sheet out and the lamp gone the new lamp could slide into place. Now to attach the wires. Fortunately I have a soldering iron so that was going to be no problem. However the design of the ends of new lamps was slightly different to the design of the old one and it was difficult to solder a wire to both ends. It turns out that wires carrying the power from the inverter to the lamp ends are held onto the plastic strip into which the lamp fits by a tacky rubber-like adhesive so it was possible to remove and reposition them to make a little more wire available. OK, the new lamp is in the plastic strip, the wires are soldered and are stuck to the plastic strip again and its time to put the backing sheet and its strip back into the panel.

Well it slides in but doesn’t seem to sit in quite the right place. Nearly there, maybe a millimeter or so out but no matter how much pushing and pulling I did it stopped short. Well one of the problems is that I’ve soldered the power wires to the ends of the lamp connectors (that was how they were in the original) and the solder seems to be sticking out, Also, one wire is at 90 degrees to the other and these issues seem to be causing the seating problem. So the plastic strip and backing sheet have to come out again. But I know better this time. I can unstick the wires before I pull out the plastic strip because this will make it easier. So out comes the plastic strip but as I pull it out (I have the panel upright and pull the plastic strip vertically upwards) the now loose wire falls (under gravity) and touches the glass panel.

This might be alright normally but the wire is covered in an adhesive rubber gunk and traces of this are deposited on the glass!

So how do I clean the glass? Maybe I can get the panel out? I grab the glass panel and try to pull but its not moving, it really does seem to be attached. OK, lets try some damp tissue. No, its rubber and it’s just being smeared. Oh, well, lets come back to this problem. So the wires are re-soldered, positioned better and the backing plus strip replaced in the panel. It fits better but not perfectly but with a bit of extra pushing it snaps into place. Great, put the panel back into the frame, re-stick the plastic adhesive to the frame (well sort of), fit the inverter and it’s done. Re-attach the connectors and earth connection, switch the laptop on – nothing. The machine boots but the screen is dead. Maybe that it “snapped” into place was not such a good thing.

Taking it apart again was easy because there were no more surprises. OK, the lamp has snapped. At least it explains why there was no light. And its a good job there’s a spare. It takes a few minutes to replace and re-solder the lamp and the backing slides into place. It’s still a bit out but this time I’m not going to force it and let’s see what happens. Re-assemble the panel, re-connect it to the laptop, power on and there’s light! But it’s not right. There’s splodges of surplus light at the bottom of the display (where the lamp is) and a nice gradient shading going up the screen to black at the top. It’s very pretty but wrong.

OK, that’s enough screwing around for the day. With a clear head in the morning a possible explanation occurs to me. The reason for the glass panel at the back must be to act as a conduit for the light so it’s spread over the entire surface of the display. The thickness of the glass panel is roughly the same as the thickness as the lamp. Maybe, the glass panel is supposed to squeeze into the plastic strip. It would explain why there’s so much light not going into the panel and why the light is not spread evenly over the screen.

So the panel comes apart again. Slide out the back panel and try to ensure it fits over the glass panel. As it turns out the backing sheet rolls around inside the plastic strip, making a U shape with the other side sticking out about 4 or 5 millimeters. If the glass panel sits inside this structure it might spread light better but it may also explain why the strip would not seat properly. So after a lot of fiddling the glass panel is seated inside the plastic strip and the strip put back into the panel. Woohoo! it seats properly.

Finally, the panel is re-assembled and connected. It works, the light is evenly distributed. But although the smear from the rubber adhesive can’t be seen, my finger prints are all over the glass panel which conducts the light (from trying to get it out) and can be seen when the display is lit. Now I know why those on sites showing lamps being changes the people wore rubber gloves!  Hey, maybe there’s an idea here for making laptops more theft proof!

So, what are the lessons? It’s not economic to replace the lamps. It seems a waste to bin a $250 display because a $15 lamp needs replacing. But it took half a day to replace the lamp, and since time is money it would probably have been cheaper to have bought a new screen. Plus it would be under warranty.

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Reader Comments

COngrats. I gave up after the new bulb broke in my hands just from not wearing gloves. The grease in your hands can be enough to blow the bulb. That was enough for me. I am glad i did not order another bulb. I am sure i would have the same result.

After reading this, I’m sort of glad the failure mine had was to go completely ‘white’. Thus, the light wasn’t the problem with mine and the only feasible option for me is to replace the whole LCD panel assembly.

Thanks for the detailed post. I will heed your warning and replace the the display. Time is money!
Thanks

Kai, good call.

So despite the difficulty and danger, were you pleased with your result? Was the new backlight significantly brighter than the old one?

Hi Tom

I was not pleased with the result.

Please that it worked and, yes, it was brighter. But the time, effort and finger prints meant the result was really below standard. In the end I spend thre 120 and purchased a new one.

I am pleased with this replacement screen.

I’m sorry to hear that. Thanks for sharing your experience.

I just did this same repair, came out ok. A little bit of light variation at the very bottom of the screen but still totally useable. Separating the lcd layers was the hardest part and if I do it again I’m pretty sure I could get it totally right, I bent the white flap on the bottom because I thought the back 3mm thick plastic layer was glass and didn’t want to flex it too much.

I agree with you that if I did it again I’d do it much better – largely because I now know how it’s constructed. But it would still not be quick or a good use of time when the cost of a replacement screen is not that expensive. I guess it brought home that time is not free.

Great post! I replaced my backlight once. I used http://www.ccflwarehouse.com they sell the ccfl lamps, but they also let you send in your whole lamp assembly and they do the repair and mail it back, saves the soldering and some of the other harder steps.