No Backlight on LED screen

So I have Sony Vaio PCG-71911M which initially would only stay lit in a certain position of the screen and when you move it it would go black.
After I opened it to check on the cable connection it went completely black: backlight is gone as I can see the screen with a flashlight.

So I opened it and this is the fuse in question I believe:



I tried to bridge it by using a tool I made out of a tweezer, paperclip and insulation tape, but the only thing I get are little sparks when I touch it. The backlight did not turn on.



I use a multimeter to test for resistance and it starts from 6MoHm and goes all the way to 11MoHm.
I also tested for Voltage, but I am unsure how to test each end. I touched one probe at one end and the other probe on the other end it read 18.26V. When I swap them around it goes to -18.26V.

 

Tom again, with a report back, GOOD NEWS

The Vaio PCG-71315L LED is working excellently
with the help of ngvuanh pointing out the fuse for
johnyb98 on post page 10 - Two different Viao
laptops with the same motherboard.

My method was to fully remove the motherboard to get to the fuse
close to the LVDS connector - bottom of the MoBo - LVDS con is top of
the Board, my previous posts piks.
Here's how -
I used a 4 inch strand of copper wire from an extension cord/speaker wire.
Though I needed 1/16th of an inch, the rest I used as a steadying handle.
Strands are thin, so I looked for a slightly thicker single strand in my old cables.

I used flux and soldered the strand ahead of attaching the strand
to the board - I did add
a small amount of solder to the fuse ends with my self sharpened
soldering iron.
I then lay the strand across the fuse without removing the fuse after
bending the 4 inch strand into a stable position I could control.

This avoided "Guess Soldering" as the solder did flow easily,
then clipped off the excess length of copper strand.

Feeling the usual apprehension, put all parts back together
and it worked.

A good multi LED flashlight and a jewelers loop
will make things easier.
Thanks to
NBR for hosting - ngvuanh for experience & johnyb98 for posting ..Tom

 

wow, it worked.
thanks for the help.

 

You can't bridge the fuse while laptop is running.
You have to use solder iron and lead to bridge before turning on the laptop.
To read voltage on the fuse, touch (+) probe of multimeter to either end of fuse and (-) probe to ground such as any hole on the board.

 

I put a working screen and the backlight is not working too, which means the problem is not in the screen itself.

In regards to the fuse I read the voltage and it is 18.8V on one end and 120mV on the other.
Is this the right fuse btw? Do I need to look on the other side of the board?
Is it certain that if I solder the fuse it will work?

I also spoke with an authorized Sony Repair Centre and the guy on the phone said that if the screen was flickering before it means the fuse was OK and probably a short circuit made it blow.
He suggested that the screen cable might be the problem and I whould probably change that first before replacing the fuse as if I don't it will probably blow again.

But the only place I can find a screen cable is Ebay and the price is £30 which is a bit too much.
There are other cables for below £5, but they are for PCG-7X1M or PCG-7M1M, so maybe they are not compatible?

Any ideas?

 

You have a blown fuse if both ends do not read the same.
I could be cable, but mostly not because most people have the fuse blown after replacing cracked LCD which meant improper handling.
If you have multimeter, plug LCD cable in and check resistance at the end that reads 0V (120mV in your case).
If it is not 0 Ohm, then you are good to go.

 

Sorry, but can you clarify on what to do exactly?
Plug both ends of the LCD cable (in the screen and in the motherboard) and measure resistance at both ends of the fuse?

Thank you again for your time.

 

Yes, this way is to check if there is any short circuit on LED power supply.

 

I checked voltage and resistance:

With display cable unplugged there is no resistance between the fuse. There is resistance between the left end of the fuse (input) of 20Mohm and dropping and no resistance on the right end (output).

Voltage reading shows 18.91V and the left end (input) and 16mV on the right end.

It looks like the fuse is gone, so are you absolutely sure that just bridging would be OK?
Maybe it needs to be replaced by de-soldering the old one and soldering a new one? Any idea what kind of fuse it is?

Any ideas?

 

Fuse is gone.
I am not sure by "no resistance".
If you have analog multimeter and needle doesn't move to all the way end, then you are good to bridge the fuse.
It is the same as digital multimeter if you see any number not around 0.

 

I have UNI-T UT60A

When the laptop is powered on with the display cable removed from the motherboard the fuse shows 18.91V on the input end and nothing on the output end, which I think means it is blown.
I've posted on another forum too and was advised not to bridge the fuse as this might lead to further problems.
Isn't it best to replace it? Can you confirm the current rating please. I was told it is 1Amp.

Any of these 7 is the a suitable replacement?

 

If you can replace it, it's the best. However, not everyone can do it because the fuse is small and the pads can be damaged during removal.

Sent from my C6603 using Tapatalk

 

the backlight of my laptop is off. Can you help me to find the fuse of Led power.

 

Which is the best method to remove a small fuse without damaging the pads?

 

The fuse is circled in red.

 

Only using hot air or infrared rework stations won't damage the pads but I think you don't have them.

 

thank you, I fixed it.

 

Thanks
Fixed my vaio

 

Thank you for your answer. You are right. I have neither.

 

Please help. I didn't have images in my prior post. I have a Sony Vaio VPCEA3BFX with no backlight after screen replacement. I thought perhaps post #3 would also apply to my issue. In the attached picture of the under side of the motherboard, there is a green fuse labeled F14 which I circled in red. Would this be the fuse I need to replace/bridge?

 

Yes, F14 is LED back light fuse. If you don't have back light, check it first.

 

I read through all posts and did not find anything about my laptop. I have a pcg71c11l vpcel17fx and the backlight stopped working. I'm trying to locate the fuse but had no luck. Please help

 

Welcome to Flickr! here is the picture

 

ngvuanh, can you let me know what fuse to bridge? Thanks!

 

This is a picture of the other side of the lcd plug http://m.flickr.com/photos/116190798@N08/12257789146/lightbox/

 

I believe F4901 1.1A/24V is the one. Try it first.

 

How about the F2 from the first picture?

 

This is the picture I'm talking about. Welcome to Flickr! the F2 is right next to the lcd connector

 

F2 rating is 0.2A/24V, so it's not back light fuse.

Sent from my C6916 using Tapatalk

 

I need help my sony vaio VPCEE21FX .....No backlight after screen replacement ...im trying to locate the fuse but i don't find it..

 

Can anyone indicate me where the blacklight fuse is? I have exactly the same problems...

thanks

Nikolas

View attachment 108944

View attachment 108945

 

It is F4 with marked N inside the corner of lcd and power connectors and golden screw hole.

Sent from my C6916 using Tapatalk

 

Hello everybody!

Thanks for this topic, it save me a lot of worries.
I changed screen at my friend's Vaio PCG-71811M and got dark screen after that.
With help of this thread and ngvuanh wisdom [thanks Man!] i repaired it in few minutes.

For anyone who is wondering how to solder over the fuse I want to share photos of my work:

1) BEFORE, F4 Fuse with "H" letter is making my issue:


2) AFTER:


3) FINALLY, ENLIGHTENMENT!


[At this model you only have to take off the bottom cover.]

Thanks again!

Greetings!

 

I got a vpcca23fx with no backlight after screen replacement. Any help please

 

ngvuanh here is my board is a vpcca23fx and have the same problem. Screen changed but no backlight. If i put the old one i got backlight but no with the new one. U think is the fuse?

 

The fuse is on the other side of this model. Please take a picture around underneath lcd connector area.

Sent from my SGP312 using Tapatalk

 

There is a picture of the whole board.

 

As I said, the fuse is on the other side of the board. You have to remove the board and take a pic on the other side underneath lcd connector.

Sent from my C6916 using Tapatalk

 

Hi to all I need help with my Sony vpcsa3c5e vpc-sa3c5e

This are the pictures of front and back of the mother board.

The main suspect are the N second photo..

http://www.pk25.com/monivideos/IMG_3084.JPG

http://www.pk25.com/monivideos/IMG_3086.JPG



I solved this issue, This was the fuse I mount all and the screen is running now.

REgards!



regards!

 

Hi ngvuanh, my SONY VAIO TZ27 has the same problem, no backlight on LED. Replaced a new screen but no luck. Please advise where is the fuse. Thanks.

 

I don't know what to do. if ngvuanh don't help I must go foward.. Any idea?. what connecto of the mother board to check?.

regards!

 

hello
i'm from belgium
i have the same situation here , my laptop is compaq 515 can anyone tell me where is the fuse in this model? i searched everywhere i haven't find .? can anyone help ? thanks ....

 

Well, first of all thank´s to ngvuanh for his time , when i do the bridging to the "S" fuse the laptop does not turn on , when i remove de bridge the lap top turns on again i don´t know what to do ¡¡please help!!

 

the lap top is the SVE14

 

Hey I have the same problem. No Backligth after Display change. I dont removed the accu :-(((

The Number of my Board is MBX - 239

What fuse i must bridge ?


//

//Edit
Fuse F15 bridged - Works

 

I am having a similar issue with my gateway NV55S02U the backlight went out on the screen so I replaced it with a new screen and could only see the image with a flashlight. I then replaced the display cable after noticing a little burn mark and this didnt fix it. Seems like might be the same issue of a fuse on the motherboard, can someone help me identify which fuse would power the backlight?

 

I circled the fuse in red.

 

I can't see anything with a small picture and whole board.
You need take higher resolution picture and focus to a small area around LCD connector from both sides.

 

I need a higher resolution picture with steady hand.
You should take picture the area around lcd connector on both sides.

 

Please let me know if these photo's will work for you, Thank you