ASUS X54H laptop no backlight

[flat-earther]

Once upon a time I was casually browsing the World Wide Web with my ASUS X54H laptop which was sitting on my desk, when suddenly the screen turned black!
After several seconds, the screen turned on again! And so I continued to use my laptop as usual.

Some time later, the screen went black again! And it hasn't lit up since.
So here I am on a journey to repair it.

Not being an expert on how to repair, what I have done is searched the internet for help on a laptop screen not working, and I have checked some things.
I found out that with a flashlight pointed at the screen I can see an image on the screen, so I concluded the backlight is not working.
An external monitor connected with HDMI cable works.
CMOS battery tested with multimeter works.
Reconnecting screen cable at motherboard and screen didn't help.

Also by the way, since the screen stopped working, with the computer turned on, when I close the screen, the computer doesn't go to sleep anymore as it normally does, so I thought the lid switch(which also is the power button) is faulty. So I was able to order a new lid switch/power button and replaced it but nothing changed.

Also by the way, although I can still turn on the computer, it now doesn't turn on easily by a single press of the power button as before. I have to press the power button several times or keep it pressed longer for it to turn on.
But once the computer has successfully turned on, when I want to shut it off, a single press on the power button suffices to shut off the computer as usual. (This behavior is same with both the original and new power button)

(BTW a history note, year ago I once forgot to remove the battery before disconnecting the power button ribbon cable from the motherboard and so the ribbon cable plastic tip melted because it got misaligned on the MB pins while moving it. I replaced the cable and everything worked without an issue ever since.)

Then using my multimeter I found a blown fuse with no continuity on the screen circuit board. I wondered that something might have blown the fuse but I don't know how to determine what since I'm not an expert.
Anyway, I found out it was a slow blow 1.5A SMD fuse, I found those online and ordered them, and with my knowledge all I was able to do is replace the fuse and see if the screen works or will the fuse blow again.
So actually I ended up soldering the new fuse on top of the old one because I'm such a beginner so I just wanted to install the new fuse and didn't want to try and remove the old one because I don't have hot tweezers which I think is the correct tool for that, but I got it soldered successfully!
After that I turned on the computer and the screen was still black, so I shut it off and checked my newly soldered fuse and it has blown!

So after that I yet again went back on the web to search where could I get help, and I found this badcaps forum so here I am. Can you help me with what to do?

My multimeter beeps and measures 7ohm resistance on two components on the LCD board which I think may be capacitors, does that mean anything?

photographs below
model: X54H/X54HR-SV168V
MB Ver. K54HR under laptop sticker but K54LY REV. 2.1 written on motherboard

[mon2]

Re: ASUS X54H laptop no backlight

7 ohms to ground is a low resistance for the T-conn board.

With no power to the board -> flux and hot air remove these 2 caps. Then measure the resistance across the same PCB pads after the parts have been removed.

These are non-polarized caps so the orientation does not matter. It will be a good idea to also check their resistance when the parts are on your work table to confirm that they may be shorted or not.

PS: I work for Jaffa oranges - cannot wait till they are available locally in the spring time.

[flat-earther]

Re: ASUS X54H laptop no backlight

Greetings mon2
Okay, thanks for that information, whatever T-conn is. I'm not familiar with the parts on circuit boards, I barely can identify them so I need help on how to find the problem or how to check for a failed component. BTW if you or someone wants to have a Skype video call and help me live on how to check the components tell me.

I don't have a hot air gun to remove those caps but I have a ''hot blow'' tip for my butane soldering iron is that okay instead? Or better just use regular soldering tip.
I have rosin paste flux; also 60/40 & 63/37 solder, is there preference which solder to use?

[ktmmotocross]

Re: ASUS X54H laptop no backlight

Greetings mon2
Okay, thanks for that information, whatever T-conn is. I'm not familiar with the parts on circuit boards, I barely can identify them so I need help on how to find the problem or how to check for a failed component. BTW if you or someone wants to have a Skype video call and help me live on how to check the components tell me.

I don't have a hot air gun to remove those caps but I have a ''hot blow'' tip for my butane soldering iron is that okay instead? Or better just use regular soldering tip.
I have rosin paste flux; also 60/40 & 63/37 solder, is there preference which solder to use?

DONT TRY THAT "hot blow" u will damage board.

[flat-earther]

Re: ASUS X54H laptop no backlight

DONT TRY THAT "hot blow" u will damage board.

Okay, I wasn't sure so good to know, thanks.

[flat-earther]

Re: ASUS X54H laptop no backlight

Okay guys I have an update. I removed the two caps like mon2 told me.
I placed flux on the 2 caps and used my soldering iron with a ''hot knife'' tip which is large enough to melt the solder from both ends of the capacitor holding it beside it and then removed the caps with tweezers. It worked great.

After removing the caps, I measured resistance across the same PCB pads and there is no continuity or ohm reading at all.

Then I looked at the removed capacitors and noticed one of them looks damaged. I measured resistance and the undamaged one has no reading and the damaged one has 7.3ohm. What do the readings mean?
Maybe the damaged side was on the bottom of the capacitor so it wasn't visible while on the board?

Do you guys think that damaged capacitor is the culprit?
Anyway, I need to search where to get a replacement capacitor, oh and replacing that blown fuse again.

[mon2]

Re: ASUS X54H laptop no backlight

Very good work.

Take a close up picture of the pcb pads that show where these caps were soldered. Post it here.

Yes, the capacitor with the low resistance is defective and causing the shorting event.

The cap with the higher resistance can be placed back.

Before you do this, does your meter have a capacitance scale? If yes, measure the capacitance of the good cap.

You will probably be ok to test this board again after soldering back the good cap. Your pic will confirm if the bad cap was in parallel with the good cap or not.

[flat-earther]

Re: ASUS X54H laptop no backlight

Thanks. Good cap capacitance measures about 2.3microfarad, reading doesn't want to settle and varies a bit(first it was 2.27 then a bit over 2.3), is that normal when measuring capacitance?

[mon2]

Re: ASUS X54H laptop no backlight

Yes, it may be ok and could be just a 2.2 uf capacitor.

Leave the shorted cap OFF the logic board and test without this cap. Post your results.

[flat-earther]

Re: ASUS X54H laptop no backlight

Greetings all.
I ordered a replacement capacitor and waited for it to arrive and it arrived recently.
I have now soldered the old and new capacitor, and new fuse.
Now there is backlight. But for some reason the light is blotchy accross most of the screen and it looks awful. Seems like something is damaged.
I wonder what caused that. Could I have caused that? I wonder if my handling of the screen somehow caused it. Tell me your opinion.

[flat-earther]

Re: ASUS X54H laptop no backlight

Hey guys, it's the next morning, and the blotchiness has disappeared completely! Thank God. Also thanks mon2 for your help.
I realized what caused it. It was my fault. I was cleaning the flux after soldering using ethanol with cotton swabs and toothbrush; but that was not the cause. The swabs and toothbrush were not enough because the flux spread to the LCD cable connector on the PCB and it interfered with plugging in the cable, so what I did was I held the screen tilted, put a piece of paper below hoping to catch overspray, and sprayed contact cleaner liberally into the connector area which cleaned it. But what I didn't realize is that the paper evidently wasn't enough and the contact cleaner spray has to have dripped down and reached the edge of the screen and got between the screen, so that has to have been the cause of the light being uneven because there was liquid between the screen!
I'm glad it has now dried overnight and didn't end up causing harm. What a rookie mistake though.

So the screen looks great apart from one spot on the lower right area, there I see a round area that's darker then the rest of the screen. Behind this area are the 2 capacitors I soldered. So I guess the heat from soldering got absorbed under the PCB and damaged something. Seems like another rookie mistake I did. I guess I should have put some spacer between the PCB and screen while soldering to protect the screen from the heat.

The power button problem I still persists. I have to press several times until the computer turns on. Again, this is only when turning on, when turning off a single press works every time. If anyone knows how that can be figured out I will appreciate your advice.

[flat-earther]

Re: ASUS X54H laptop no backlight

I found out why the power button wasn't working properly. When I replaced the old power button ribbon cable I bought a ribbon cable where the contacts on either end are on same side while the original cable had a ribbon cable with contacts on opposing sides.
At that time I didn't realize that is an issue but I later did and once replacing the ribbon cable with the correct one the power button works like it should.

The connection has 6 pins and to power on the computer the two middle ones ie. 3 and 4 have to be shorted, so inverting the pins still leaves pins 3 and 4 in the middle so that's probably why it still somewhat worked to start and shut down but didn't function properly.