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The ASUS N550JK-DS71T is manufactured by ASUS. It is a portable computer and is good for mobile use.

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New laptop screen has no backglight

Hi guys,

my laptop (Asus N550JK, with touch screen - digitizer on the top of a matt lcd) Lcd broke down few weeks ago (purple/green tint etc) after some test i got convinced that the screen was faulty and decided to change it.

The screen is lg philips lp156wf4-sph1 (written on it) and it seems to be matt and IPS, so i ordered one online and installed it (I received a BOE screen), the display "works" but there is no backlight.. so i don't see anything, appart if i put a strong flash on it..

I find another seller, order another screen.. i receive the same screen.. same issue ! no backlight..

I dont know what is the problem, the when i pug in the former damaged screen (an LG philips) the backlight works smoothly (but the screen is broken heh.. as the former still has backlight, issue does not seem to come from motherboard, or lid switch)

What could be the cause of it .. ? Thanks in advance for your precious help

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One of the screen is boe nv156fhm-n42

according to the data sheet the on off pin is also on 22, the other screen is HB156FH1-301 (I was not able to find any datasheet for this one).

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Hi @ramoglio123,

Did you find solution to your problem? I also have an N550Jk and I'm having the same problem. The new display works, no backlight.

Thanks!

von

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Hi @ramoglio123

When you say “I find another seller, order another screen.. i receive the same screen.. same issue ! no backlight..” what do you mean? The same screen as the original or the same as the 1st replacement screen that didn’t work?

It may be that the replacement screens wiring connections are different to the original screen.

Here’s the datasheet for the original screen. On p.8/31 there is the cable pinout information. It shows that the LED backlight On/Off wire is on pin 22. This is the lead that is used to signal the screen to turn the backlights on and off. The power for the backlights is always available at the screen (see pins 26-29) and the backlights are turned on and off as required by a signal voltage being applied or removed on pin 22 as required.

If neither of the replacement screens are the same model as the original you would have to find the datasheets for those screens to check what their cable pinouts are to see if it is compatible or not. Search for (insert full make and model number of screen) pinout to hopefully find the datasheet

Since the original screen backlights still work when it is connected it is not a backlight power supply problem from the motherboard, it may be a compatibility issue instead

Here are the parts for your laptop. If you click on Category > Display you will find the part numbers for the screen. If you search online using the Asus part number only, you will get suppliers of the part. At least it should be compatible.

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Hi,

Thanks a lot for your answer, yes it seems that both the screens i received are from the BOE chinese company..

I was not able to find any other brand elsewhere, i will check for the pin no, thanks a lot!

Apart from that do you think there could be another issue?

von

@ramoglio123

Not really.

Since you can see an image on the screen OK with a torch and the backlight still works with the original screen then it seems that either the backlight power is connected on different pins into the screen or maybe the backlight on/off wire is on a different pin but without the datasheet it would be difficult to know which.

Whatever the case it seems to be that the screens are incompatible with the laptop. Even though they have a 30 pin cable doesn't mean that they're wired the same

As suggested if you search using the Asus display part number from the parts link there are suppliers. You may be able to verify which screen is the same as the original (as there are a lot of displays in the parts list) by seeing if the "Asus part number" is also printed on the back of the original screen

von

One of the screen is boe nv156fhm-n42

according to the data sheet the on off pin is also on 22 https://datasheetspdf.com/pdf-file/12944...

the other screen is HB156FH1-301 (I was not able to find any datasheet for this one).

von

Also, I have tried to identify the screen on Asus website, i have not been able to, on the original screen i see the below stickers:

AS 131290350346 70N0QX1P1000

132030370091

6091L-2436E

140402 JEK

QETE424H5EKJG2436E2

but no result ..

von

@ramoglio123

On the LG/Philips panel datasheet it says that the LED enable High voltage is between 3V and 5.3V and the LED enable Low Voltage is between 0Vand 0.3V whereas for the BOE panel it simply says 3.3V. so you'd think that it should work

It could be that the BOE panel is still faulty just because the pinouts are the same (there is one difference the BOE has a Hsync wire on pin 24 which the LG doesn't).

Disconnect the video cable from the motherboard and if you have a DMM (digital multimeter) use its' Ohmmeter function to test between pin 22 on the cable plug and an earth on pin 16 or pin 21 and measure the resistance. Do this for both the LG and the BOE. There should be a reading, hopefully similar between the two panels which at least proves the wire from pin 22 is connected to something in the panel electronics and not open circuit. You know that it is OK in the LG panel as the backlight turns on but you don't know for sure that it is in the BOE panel although I suspect that it will be given that the other replacement doesn't work either.

Other than that I don't know what to try, except maybe getting another panel using the Asus part numbers. It should be compatible in every aspect

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ramoglio123 wird auf ewig dankbar sein.
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