dell inspiron N7110 LCD no back light

bigsam731 · Oct 7, 2016

Hello all. I'm new to the community and my apologies if this was discussed in a previous post. I have a Inspiron 17R N7110 that has dim backlight to the LCD. When I plug it it to an external monitor i can see everything in that monitor. I searched every where for a solution but nothing on my model, all I find is solutions for the 1545 model which tells me to replace the F1 or F8 fuse. If that's the case on mine, does anyone know where are those fuses located? thanks in advance

My motherboard model is
DA0R03MB6E0 REV; E

webworkings · Oct 8, 2016

It could be the fuse or it could be the backlight lamp.

Is the device still under warranty? If yes, I would contact the manufacturer about a repair or replacement.

If it isn't under warranty, then it is up to you if you wish to try and do the work yourself, or have someone else do it.

lolimstupid · Oct 8, 2016

Do NOT open it up and try to fix it yourself until you call to check on the warranty. If still eleigible they'll just send you a new one, but opening it up yourself could void the warranty, oh and I think it's the backlight itself not a fuse.

jarotech · Oct 8, 2016

bigsam731 :

Hi, sorry to say, but depending on the configuration of your laptop, you do not have a fuse for the LED backlight. It will be easier to change a fuse, but you have different components controlling the power for the LED backlight. The problem could be the display cable, sometimes they become damaged in the hinge area. But if the laptop is still under warranty, use it.

bigsam731 · Oct 12, 2016

Thank you all for the replies. I should've mentioned that the laptop is out of warranty. I also did a few thing to pin point the problem. I replaced the LCD and the cable but have the same issue. I also took the LCD screen and tested it in a different laptop and it works fine, which lead me to think that its something on the motherboard. I'm trying not to replace the motherboard because everything else works great. I also got my hands on the schematics for the motherboard but unfortunately I don't know how to read it.

jarotech · Oct 12, 2016

If you look on the motherboard, do you see a transistor (chip with 6 pins) with a number Q43 written in white beside it on the motherboard?

bigsam731 · Oct 13, 2016

jarotech :

Are you talking about this?
http://

jarotech · Oct 13, 2016

bigsam731 :

Yes exactly, so, on your motherboard you don't have this transistor and the R168 resistor. Which Quanta schematics do you have? Also do you have a multimeter to read voltages?

bigsam731 · Oct 13, 2016

jarotech :

Yes I have a mulimeter to read the voltage and i can send you the schematics if you need it. I'm attaching the first page of it if that help.
https://drive.google.com/file/d/0B4eDDk7o_vmnemdhaUY3c2dUd0U/view?usp=sharing

jarotech · Oct 14, 2016

Just to be sure, what is the number on the U14 chip. Measure the voltage on one of the pins 38,39,40 (they are all connected together) at the LCD connector on the motherboard.

bigsam731 · Oct 14, 2016

I tested the voltage and i got 19V on the pins. as far as the U14 chip, i could not find it. i found U15,U13, and PU14 but not U14. Can you give me general Idea on its location. Thanks in advance.

jarotech · Oct 15, 2016

Don't worry for the U14 chip, I just wanted to know if you have the correct schematics for your laptop. What voltage do you read on pin 3 of JP1 connector?

bigsam731 · Oct 16, 2016

I got 3.3V on pin 3

jarotech · Oct 16, 2016

All good, what do you have on the diode D12,

1-
----3
2-

pins 1,2,3.

bigsam731 · Oct 16, 2016

jarotech :

I found the D12 diode but not sure how do want me to test it.

jarotech · Oct 16, 2016

Measure the voltages from pin 1 to ground and 2 to ground and 3 to ground like you did with pin 3 on JP1.

bigsam731 · Oct 16, 2016

jarotech :

pin 1 = 3.3
pin 2 = 3.7
pin 3 = 3.1

but when I re-measured i got 7.1 on pin 2

jarotech · Oct 16, 2016

Now, measure pin 36 on the LCD connetor on the motherboard.

bigsam731 · Oct 16, 2016

jarotech :

4.4V

jarotech · Oct 16, 2016

All the voltages are good, measure pin 2 and 4 on the LCD connector.

bigsam731 · Oct 17, 2016

jarotech :

they both have 3.3V

jarotech · Oct 17, 2016

Are you certain the cable for the screen is good, because from what I deduct, all the voltages for the screen are good, you should have the backlight on.

bigsam731 · Oct 17, 2016

jarotech :

I've replaced the cable before. Could it both cables are faulty? Just to be sue I'm going to check the continuity on the cable and let you know.

bigsam731 · Oct 18, 2016

Ok. I got continuity on all the pins on the cable except pin 1, 34, and 37. But when I lifted the protective tape, I noticed that those pins did not have wires that leads to the other side.

jarotech · Oct 18, 2016

The pins 1, 34 and 37 are not connected on the motherboard, so the cable don't use them.

On the connector for the screen you have those voltages on the pins.

Pin 40 - 19 volts
Pin 36 - 4.4 volts
Pin 35 - 3.1 volts
Pin 4 - 3.3 volts
Pin 2 - 3.3 volts

Also on pin 3 of the connector JP1 you have 3.3 volts.

dell inspiron N7110 LCD no back light

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