Need help finding LED backlight fuse [PICS]

[selldoor]

Re: Need help finding LED backlight fuse [PICS]

In the middle of the connector in pic 1 what is that connecting 2 pins?

[selldoor]

Re: Need help finding LED backlight fuse [PICS]

This is not a fuse or a 0 value resitor as the other fuses has P or pl symbol on it and the jumpers has 0 in the middle. .

F6 is a fuse and has an N on it - did you test that one? did you also check voltage at each side with respect to ground as well as ohms/continuity?

[memalt01]

Re: Need help finding LED backlight fuse [PICS]

Thanks sorinac, this is excelent motherboard schematic and matches the LED side of the connector voltages on the LCD specs. I will check it closely tonight and measure all the voltages in each pin on the motherboard LCD socket. When I closely look at the schematic, it seems like all these LED backlight power is coming from the GPU chip and there is no fuse in between. However, if there was a slight problem with the GPU then I wouldn't get picture on external monitor. I will check the capacitor's and the resistors tonight with this motherboard by using the schematic.

Thanks for commenting on this selldoor but the pic1 and 2 are from back of the LCD screen which is good as I already tried two good LCD's. I actually hooked this LED screen to another laptop and worked perfect The fault is in the motherboard as I have changed the LCD cable and the LCD screen.

[memalt01]

Re: Need help finding LED backlight fuse [PICS]

I checked the LCD connector on the motherboard for backlight voltages and according to motherboard and the lcd schematics some of the readings that I am getting are wrong. pin 40, 39, and 38 should be a backlight Vbl = 6V~24V but 39, 38, 37 and 36 are grounded and pin 40 is not connected (nc) and that is totatly wrong according to schematics. Pin 1 is NC and 2, 3 and 4 are 3.3V which are right. I checked this voltages while connected to the lcd and while it is not connected to the lcd. It could be problem with inductor FBM2125 HM330-T but how to find this? Can you see this inductor from my previous pics? Or even the capacitors C1, C2, C3 and C5. So I have 5 components to find and check to fix this problem I wish

I attached a view of the lcd socket from back of the motherboard. Hope someone would come up with right idea. I think I am looking for a component that is short rather then open.

[memalt01]

Re: Need help finding LED backlight fuse [PICS]

This is the LED socket on the motherboard again. pins 39, 38, 37 and 36 are ground but they should't be ground according to specs and the schematics. and pin 40 is NC. If I don't know better I would say the problem with the connector but nothing internally or externally damaged within this socket. Pin 36 is going to the ground (you can see me removing some of the paint from the copper on pin 36) but 37, 38 and 39 going no where eventhoug they are grounded somehow!

[Telephonewire]

Re: Need help finding LED backlight fuse [PICS]

I have the same problem with a Samsung NP550P7C laptop.

No backlight on the screen but I can see the image on the screen if I shine a light onto it.

I rather stupidly removed the screen cable from the motherboard whilst the batter was connected!

Does anyone have any experience of this laptop?

Any help greatly appreciated.

Jeff

[Telephonewire]

Re: Need help finding LED backlight fuse [PICS]

Here is a picture of my motherboard and a close up of the connector.

Any help gratefully received!

Jeffrey

[Telephonewire]

Re: Need help finding LED backlight fuse [PICS]

And here is a picture of the back of the motherboard...

Any ideas anyone???

[Wable]

Re: Need help finding LED backlight fuse [PICS]

X54c (K54C)

backlight is back after change the component on the circle in red

the original component i not remember but i have put a 0 Resistor

now is ok.

[memalt01]

Re: Need help finding LED backlight fuse [PICS]

I got mine fixed 2 weeks ago and now being busy with another laptop. The problem was with the connector on the motherboard. It had short right below the plastic which I suspect due to heat that has melted. It is really a big and messy job to de-solder this connector so better prepare for a spare connector which what I did.

[tres_kun]

Re: Need help finding LED backlight fuse [PICS]

I have had the same problem the past 2 days
an asus x53e
replaced charging port and no backlight
I have spent about 3 hours attempting to identify a faulty component
And while testing i disconnect the power button ribbon and it starts working
there was a short circuit in the plug
My adventure ends happy

[costin_yo]

Re: Need help finding LED backlight fuse [PICS]

Hello, I registered on this forum specially for this laptop and I see that there are a lot of good things here....

The problem is that I have the exact same problem with it, I have an Asus K53SV that I replaced the power jack one year ago and after one year because it is a common problem for this laptop the person came back with it because the power jack is faulty again. But the thing now is that the power jack was making a very low connection to the MB and the backlight is not working...I replaced the power jack again with a new one and the backlight is not working on the screen.
I think that the cause of this problem is that because of the low connection between the power jack and the MB, the screen got on/off several times (and the laptop was on battery at that time and when it is on battery and plug off the power cord the screen dimmes a little) and something got faulty on the MB.
I also checked the MOSFET and I have 3.3 volts on input and 3.3 volts on output.
I also checked the Ferrite and I have 3.3volts on both ends.
I checked the display pins and the pins 39,38,37 and 36 are linked to the ground.

In the near area of the LCD connector I have some parts that are linked to the ground on both ends. I really don't know if this is the way that they need to be or no but I have a strange feeling that this is a short circuit.
Soon I will add some more quality pictures with the MB as I will use a DSLR camera.

Please let me know what I need to measure or anything I can do to make it work.

Thank you very very much and I kindly wait for a reply...

[p4r4d0x]

Re: Need help finding LED backlight fuse [PICS]

Hello guys, and costin_yo, especially...

I have today resolved issue i have found on my K53E, that is closely relative to K53SV costin is describing... using info found here, i was able to fix it... It is second hand laptop i was intending to fix and sell for profit, so i had no idea how nicely (or badly) was the lappy treated. The fact is that once i've reassembled it (as the mobo was not the part of it), the known-working motherboard suddenly had issue with backlight... there were many causes of this problem, the LVDS cable to the screen was faulty (as even data channel to the screen was corrupted). So i've gotten my hands to replacement, which fixed screen, but didn't backlight... So i've decided to do some continuity research... and i've noticed burnt smd jumper (see photos, it's not my photo but it depicts same component) - it was replaced by solder bridge and the screen was okay now, until i've reassembled the laptop... so i've took it apart again and the screen was working again (damned gremlins...) - after reassembling and testing part by part, i've found the issue - it was short cirtuit on power button ribbon cable, caused by peeled contacts (see in photo - sorry for quality, my phone hates microscope). So i've bent them back, carefully put the ribbon to the connector and reassembled - works like charm!

TL;DR:
1) Check voltages on the MOSFET
2) Check SMD jumper marked on photo below
3) Check your power button ribbon, boot computer without it - it might be faulty (How to boot? Shorting middle pins (3 and 4) on the connector briefly using tweezers worked for me - at your own risk. Might also try powering up and pulling it out immediately...)

[costin_yo]

Re: Need help finding LED backlight fuse [PICS]

Woow, first of all thank you very much for the quick reply...

I want to tell you that I tried to search for a broken fuse on the back of the board but I cannot see any, I cannot see any fuse that looks like yours in that picture so I can change it.(I noted one of them that seems to be like urs but it seems that its working, it is in the last pic that I added)
I made some pictures to a big resolution and please give me ideas of which fuse can be broken.....
I tried to test them in that area and it seems that all of them works...

I dont have any problem with my power on cable and I tried to power it shorting the 3 and 4 pins and the same, no backlight....I really dont know what to do...

I added some good resolution pics and please make some notes of which part can be broken on it...thank you very much....

Please help me guys....
Thank you very much.

[costin_yo]

Re: Need help finding LED backlight fuse [PICS]

I fixed it too...you gave me the idea to check on that area with the mobo powered. I found the resistance or whatever is that, that is next to the indicated jumper. The brown thing. It was receiving 19volts but giving out only 6. I jumped it with some solder and it fixed the backlight.(I tested it first with something else for few miliseconds to see if its actually from there) I hope nothing goes wrong on the long term situation.

Does anyone know what is that part exactly? Where I can find it? (not from other used mobos, I want it new)

What can happend on long term situations?

Thank you very much to everyone especially to p4r4d0x for giving me the hint to look in that area...!!!

[p4r4d0x]

Re: Need help finding LED backlight fuse [PICS]

EDIT: this is not your case, as i mistakenly thought you replaced capacitor and not inductor, see my next post...

Grey-Yellow-brown components are capacitors (darker colour means higher capacity), considering their purpose, they are not meant to pass continuity (unlike inductors or resistors) - and they will allways pass it only briefly (when they are charging) - considering you havr shorted those pins and it works, you either replaced faulty power rail with working power rail (or with same rail, ommiting part of circuit). This might cause issues, i.e. Further damage to the board in long term use, overload of the said power rail when the demand from device that uses it increases, etc.

In your situation, i would try to measure current trough the solder bridge with disconnected screen, and if it doesn't exceeds big deal (less than 200 mA or something - really a wild guess) it might be fine to let it run like this...
You might also consider breaking up the circuit somewhere on the net, in attempt to disconnect faulty power source, as there was clear voltage difference (19 volts minus 6 is still a lot) and it might consume lots of power, which is waste and might shorten battery duration and/or further damage your board. Assuming you are using same net as ground fo both voltages. Fiddle with it a bit, you can't do irreversible damage if you just desolder something and solder it back in case it "wasn't it".

Sorry for my poor English, as I rarely talk about electronics in English... And also sorry if this doesn't make much sense to you, i'm on my phone at work, and can't rephrase it atm, will look here in the evening, so let me know if you need to clarify something, i prefer drawing while talking as i'm not very good at explaining, but that aint possible over internet

[p4r4d0x]

Re: Need help finding LED backlight fuse [PICS]

Oh, just looked at thr image, the brown thing is not brow at all, its dark grey and those are inductors, it serves as a choke, that prevent big power surges, it might slightly decrease lifespan if replaced by solder bridge, but will work well and with no problem... You might ignore my previous post, as it is regarding capacitor replacement (on case you ever find faulty cap, never replace it with solder or jumper, it might do serious harm) and not choke... If you consider replacing it, it will not be really easy to find proper value, but someone experienced at your component supply shop might "guess" it well. As smd inductors tends to have very inaccurate values, it might as well don't matter. After all, you're just putting DC through it, so worst thing it might do is just delaying the current for ms or two, essentially making no harm ..

If the choke gave different voltage on both sides, it was definately KO...

[p4r4d0x]

Re: Need help finding LED backlight fuse [PICS]

(damn, doublepost, sorry)

[costin_yo]

Re: Need help finding LED backlight fuse [PICS]

hehe...I feel relieved now that I read ur second post...because I already assembled the laptop. yes, i have seen a slightly difference when powering it up...i mean the backlight had a little delay when powering on....(especially when i move it from battery to power cord)
i tested the backlight in windows brightness and it works well...
i will reinstall windows later and see if all goes well keeping it wired and on battery also...
i i really dont know where I can find that part without a proper schematics of the board.

thank you and I wish you have a great day...later I will add a pic with the exact part so you can see it and know exactly...

[p4r4d0x]

Re: Need help finding LED backlight fuse [PICS]

Most likely the screen is waiting for the voltage to get stabilised... (which might take little longer on AC, as AC have way lesser maximum current than lithium cell, so it takes way longer to charge the capacitors) Nothing to worry about, it is electronically monitored and the system is cut off when something goes wrong...