Any ideas on how to properly test voltage on the LCD inverter input and output?
My Satellite 5105-S701 fails to light the backlight. I can see the image when using a flashlight and the image on an external monitor is fine. I tested the output from the inverter board and am getting zero volts. The input has many fine wires and without a pinout I have no idea how to test for voltage going into the inverter. I took it to a laptop repair place and told them I thought it had a bad inverter and would they please diagnose it for me. I guess I was too specific because when I picked it up they simply told me the inverter was OK and handed it back to me with the backlight still not working and no idea why it’s not working.
Any ideas on how to properly test the inverter input and output? I would try a known good inverter but I don’t have one. Any other suggestions as to why the backlight won’t light? Or any other tests I can run? I’ve found all the software backlight controls and they’re all cranked up. Thanks for any help!
That’s a question I keep asking myself over and over. How can I test an FL inverter board using just a multimeter? Unfortunately, I do not have any straight answer at this time. I believe that you can measure the voltage on the input if you connect the positive probe to the pin 1 on the FL inverter and the negative probe to the laptop chassis. The multimeter should be set to test DC voltage. I think that the voltage on the input could be somewhere between 9-30VDC, just in case set the multimeter to a higher voltage. The pin 1 on the FL inverter board should be marked; I’ve seen it marked before. You should get some voltage on the inverter input. If you get zero volts on the input, then it’s possible that cable is bad or the connection on the system board is bad. Now about the output voltage. I believe that you can get an accurate readings on the FL inverter board output only if it’s loaded properly, in other words if the backlight bulb is connected and it’s in a good working condition. It could be a very high AC voltage. I would set the multimeter to at least 1000VAC. Be careful, it’s a very high voltage and if you do something wrong and short a circuit, you can permanently damage the laptop. Sorry, but I cannot provide more specific information. If you find any info on how to test a failed backlight with a multimeter, please let me know.
Usually, when I have a problem with the backlight, I unplug the screen and connect my test backlight bulb. If it lights up fine, then the backlight in the LCD screen is defective. If it doesn’t light either, then most likely it’s the FL inverter board fault. Video cables do not fail very often.
December 28th, 2006 at 11:31 am
Any advice for removing pressure marks from an LCD screen – not afraid to dismantle screen but would like to know if there is anything I can do ?
My laptop is a Lenovo T20. Possibly caused by the screen being pressed against something when closing the lid or from the top of the laptop having something pressed against it whilst closed.
December 26th, 2006 at 1:06 pm
Hi,
My laptop is HP Pavilion ZE4610US. I am planning to buy a new desktop PC. I was wondering if it is possible to use my laptop’s LCD for my new desktop PC.
Thanks…
December 19th, 2006 at 8:32 pm
Sorry Brad,
I don’t have the pinouts and have no idea where to find them. By the way, I didn’t find any Toshiba laptop where Samsung LT150X3-126 was used.
December 18th, 2006 at 1:31 pm
in reference to my question(#18), ive done a little more research and i think i can splice the cables together, but i cannot find the data sheets for the lcd’s i have, although all i really need is the pinouts. would you have, and or can get these? Also, i still wasnt sure on the inverter deal, i think it will power the other bulb, but i can maybe swap bulbs as well. heres the lcd panels i have:
LG Phillips=LP150X06 =30 pin connector (what came in the toshiba A15-129 i have
Samsung=LT150X3-126 =20 pin connector (what im trying to put in the toshiba)
thanks, brad
December 17th, 2006 at 8:33 pm
Thank You Laptop Freak
I just ordered an inverter from ebay and will try it out this week when it gets here
December 17th, 2006 at 12:30 pm
Martin,
Here’s a summary I made from you comments 22 and 23:
1. the laptop LCD screen has no backlight but you can see a faint image on it
2. the laptop works fine with an external monitor connected. You have no problems working with the external video.
3. the backlight flashes on startup and then turns off
If that’s correct then most likely you have a faulty FL inverter board. I would go with replacing inverter first. LCD inverters are pretty cheap and you have a very good chance to fix the laptop.
December 17th, 2006 at 12:21 pm
Matt Power,
Never seen problem like this before. First of all reflash/upgrade the BIOS. I guess it’s possible that the BIOS got corrupted somehow.
If I understand right, the laptop shuts down when there is a signal going from the motherboard to the LCD screen and I would assume you might have a faulty video cable (may be there is a short inside the harness). Or it might be a faulty motherboard but you cannot tell witch one until you replace at least the video cable. You already replaced the LCD screen and still having the same issue, so it’s not a screen problem.
Here’s what you can try. Unplug the external monitor and unplug the video cable from the motherboard. Start the laptop. You will not get any video, but at least you can see if the laptop boots or it shuts down. If the laptop shuts down even without the video cable plugged in, then I would think that you might have a faulty motherboard.
If the laptop boots up without video cable plugged it, do next. Plug the cable back into the motherboard, and unplug the cable from the LCD screen. Start the laptop again. If it shuts down with the cable connected to the motherboard then I assume you might have a faulty video cable.
Sorry man, I cannot tell you exactly what is wrong. It’s really hard to troubleshoot the laptop over the internet, moreover when the laptop has such an unusual problem.
December 16th, 2006 at 7:11 pm
btw when I first press the power button the light flashes
December 16th, 2006 at 7:02 pm
I have a dell 9100
There is no light on the lcd
If I look close enought I can see it booting up and get to the desktop
If I hook up a vga cable it will show me the windows logo and I can use it on the desktop with no problem
I Cant see the bios screen using the monitor so I cant change anything in the bios
What do you think I need to change?
the inverter
Video card
LCD
LCD backlight (I heard this is hard to do but I can solder pretty good)
December 16th, 2006 at 12:34 pm
i have a t30 thinkpad with a strange video problem. i can’t find any information on it anywhere. The problem is with the internal LCD, the laptop will boot fine with an external monitor but if i try to switch to the LCD, the laptop shuts down. i’ve tried a replacement LCD from Ebay, but i still get the same issue. will not boot from internal monitor, shuts down, will not switch to internal monitor, shuts down. any ideas?
December 11th, 2006 at 7:24 am
I have some issues with my Thinkpad A30P (UXGA NEC display). The Laptop once fell down splattering the backlight CC and the inverter, I replaced both and had no problems for about 2 months. Then the backlight startet acting strange, only working when the inverter got “full juice” from the mainboard, meaning when it was setting to highest brightness and connected to a power outlet. Soon afterwards, while operating with a replacement inverter to see if the problem went away I heard a fizzle and saw my screen go dark just to witness some smoke coming from the inverter.
Now – using a third inverter – I can´t get the backlight to work at all although it works using an inverter from a case CC. Additionally, the Power/charge LEDs on the inverter board don´t light up anymore. The display is working fine without any distorted pixels (though dark now) and I couldn´t find any faulty fuse on the mainboard or on the LCD board.
Any idea why the inverter seems to get no power at all? Can I get a pinout for an IBM inverter so I could fetch the needed voltage from somewhere else on the mainboard?
December 10th, 2006 at 10:45 am
I recently purchased Dell d600 laptop on ebay. SXGA display screen had several scuffs, spots, dots, etc. Seller sent another display screen with no instructions and I cant figure out how to change display screens. Can you help with instructions or direct me to helpful website? Hope you had good vacation. Thanks.
Adam
December 6th, 2006 at 2:57 pm
Hi, and great website. I was not really sure where to post this, so i figured here was best. Got a toshiba sat(A15-129) with a broken lcd. I bought a used lcd on ebay from a compaq, i had found a cross reference guide that said they were the same panel, and of corse it isnt! My questions: The main data cable connector on the toshiba is larger than the compaq lcd’s data connector, is there an adapter, or some way to splice the 2 together? Also, are FL inverters pretty much the same? can i use the toshiba inverter with the compaq lcd? thanks for your help, brad
December 5th, 2006 at 1:30 am
Thanks. I also don’t think its the lcd or backlight. firstly, in the dark switching backlight on and off is very noticable so much so that i can actually see most of my keyboard with backlight. second, the lcd is in very good condition: never had any bumps, falls, scratches and so on.
The thing about taking it to a repair shop, is that i did. he gave an estimate of what the problem may be (lcd, inverter, video board etc), but unless i gave him £60 he couldn’t be sure. I’m just worried that i give him the £60 and then he says its the lcd which will cost 400 + to fix. Is there any way of testing the video cable, or know of where i can get some parts?
December 1st, 2006 at 8:17 pm
Ambia,
If you cannot see a faint image on the screen then it’s not the inverter board failure. Here I’m almost positive.
So, what’s left? The screen itself, the video cable and the motherboard/video card (I don’t know if the graphics card is integrated into the system board in your laptop). Take a look at the generic laptop display diagram.
For some reason I think that the problem is not related to the LCD screen. I would understand if the data channel fails (no image on the screen) but the backlight works fine or vice versa, the data channel works fine (you can see an image) but the backlight fails. Yes, in this case I might suspect the LCD screen. But why both channels failed at the same time? No data and no backlight? So the problem occurs before the signal goes to the video cable?
I think that you might have an issue with the motherboard/video card. Even though the external video works fine, you still might have an issue with the video card. That’s my guess.
It’s really hard to troubleshoot a laptop without actually having the laptop.
May be you should consider taking the laptop to a repair shop at least for diagnostics? They can unplug your LCD screen and plug a test screen and tell you for sure with module is failing. If the test LCD lights up with image then you have a bad screen, if the test LCD is still “dead”, then most likely it’s the motherboard issue or you have a bad video cable.
December 1st, 2006 at 1:28 am
Thanks, and perhaps your right about the backlight. Whether in the dark or not, if you swith the backlight on and off you can see the screen get a little brighter especially around the edges, and this is more noticable in the dark. As for seeing any image, then no. However, if you turn on the backlight, in the dark, you can see a faint thick line approximately a couple of centimeters from the bottom of the screen; but that’s about all you can see.
I’ve been searching heavily on the net to find an inverter for this model but with no luck. I’ve also emailed a couple of site to let me know when they do get some in. I’m begining to think that it’s the lcd, in which case it’s either 350 + labor or a new laptop; niether of the two is very appealing.
November 30th, 2006 at 10:37 pm
Ambia,
Do you mean the screen changes from completely dark to “life” dark? You can see the difference but the screen is still black, correct? If yes, then the backlight is NOT working. With a working backlight the screen would be bright.
Turn on the laptop and look at the screen. Can you see any image on the screen? If you can see a very faint image, then most likely you have a failed FL inverter board. In this case I would try replacing the inverter board first. It shouldn’t be very expensive to find a new inverter and you have a very good chance to fix the problem.
You can find more tips in my other post: How to troubleshoot and fix laptop video problems.
November 30th, 2006 at 6:52 am
Hi
I’ve got an issue with my advent 7041 laptop. The screen doesn’t seem to work, but computer works fine with external monitor. The laptop repair shop said it could be any one of three main problem: lcd, inverter, video/graphics card. He said that an lcd would cost £350 + labor. I for one don’t think its the lcd, on the basis that its in almost perfect condition (still has (had!) screen cover). I also don’t think it’s video card since it works fine with monitor. That leaves the inverter. However, i’m pretty sure the backlight is working as you can turn it on/off and notice the difference in the dark. I’ve opened it up and pushed all the connectors about, but still prblem persists. Any ideas?
November 26th, 2006 at 8:43 pm
Hello. I have a Toshiba P35-S611 (bought a little over a year ago and warranty done). I am having similar LCD problems like a few others where the screen has gone dim. It started one day when for some reason it went dim and I noticed a high pitched noise coming from it. I turned off the laptop immediately. I waited a while then turned it on and it looked fine, but then went dim again the noise came back. Now I can’t even turn it on, just starts dim with sound. I am pretty sure it is a similar screen issue and the noise has something to do with the screen.
I’ve published this comment as a post. You can see the rest of the comment and a possible solution here: LCD screen went dim and I noticed a high pitched noise coming from it.
November 23rd, 2006 at 6:46 am
Hi
I got a Toshiba equium m40×203.recently my screen showing red lines all over the lcd as i move the mouse pointer along.i tried connecting it to an external monitor n have the same problem.flashed the bios(from some help forum) but the problem still remains.do you think wil hav to replace the video card?and if posible how.
many thnks
November 22nd, 2006 at 12:49 am
Sairam,
I cannot think of something else.
Yep, sounds like the LCD is only the option.
November 21st, 2006 at 10:19 pm
Hi,
Nope, there was nothing heavy on the bag. It was in the trunk.. it is possible i guess that it got damaged during transit but it is kind of surprising. So replacing the LCD is pretty much the only option?
-Sairam
November 21st, 2006 at 10:10 pm
Sairam,
It’s definitely not a faulty inverter. The inverter board works like a power supply for the backlight bulb and if the inverter goes bad the backlight stops working at all.
I think the LCD screen has been damaged during the travel. Is it possible that you had something heavy on the top of the notebook bag?
November 21st, 2006 at 1:21 pm
Hi,
I have a Dell Inspiton 8600. I just got back from a 5 hour drive(laptop was in the car although in a targus laptop bag) and noticed that the LCD display was dim on the top right. To debug, I tried to display a black background and noticed a lot of white light leaking in from the top right which makes the display dim on the right. I connected an external monitor to the laptop and that works fine. Rebooting the laptop doesnt help. I did check the motherboard end of the display cable and it is fastened well. Any idea what could be the source of the problem? Do I need a new LCD or is it a faulty inverter/cable? Any help would be appreciated. Thanks.
November 6th, 2006 at 10:54 pm
Miguel,
It looks like the FL inverter board (located inside the display assembly) is failing. Most likely you can fix the laptop if you replace the inverter. Here are instructions for Dell Inspiron 8600 laptop, click the display assembly link. You can find a replacement display inverter board online for about $30.
November 6th, 2006 at 8:02 am
I have a problem wih my laptop’s screen. When I turn it on, it works just fine for like 2 minutes and then it goes dim. Its not a brightness issue, I’ve tried the brigthness adjustment thing and it does not solve anything. The picture is still there, just very very opaque. I plugged a moniotr to my laptop and it works perfectl, so its not any video card problem, it must be something with my monitor. Any ideas of what I can do?
(Specs: Dell Inspiron 8600, Pentium M 1.6 GHz, 512 MB Ram, 64 MB Nvidia Video Card)
November 5th, 2006 at 12:49 pm
Peter,
If you can see the same pinkish cast on both screens – internal laptop LCD and external monitor, then the problem is not related to the laptop LCD screen or video cable. Usually this issue is related to a faulty video card or in some cases bad memory. Just in case download Memtest86+ utility and test the laptop RAM. If it fails the test, replace the memory. I have another post dedicated to a bad video output (www.laptoprepair101.com).
It also could be related to a faulty video card or RAM. Most likely it’s related to the video card.
It depends. Some Tecra laptops have removable video cards, the card not integrated into the system board. In this case you can replace just the video card and leave the system board.
On some models the video card is integrated into the motherboard and if it goes bad you have to replace the entire motherboard.
I don’t know your laptop model and cannot say if the video card is integrated into the motherboard.
Replacing the video card or motherboard is not a simple process. The laptop must be taken apart in order to replace these parts. I have created a few guides for taking apart Toshiba laptops (www.irisvista.com). Take a look at these guides and you’ll get an idea if it’s too complicated for you.
After you replace the motherboard or the video card it is not necessary to reload programs.
November 4th, 2006 at 2:18 pm
Monitor problem.
I have a Toshiba Tecra that has run perfectly for a year. It has XP professional on it.
I used it yesterday for 6 hours without a problem.
At the end of the day I noted that some areas of the image looked fractal, flickered and developed a pinkage cast.
I used the laptop to drive another monitor. I could see the problem there.
I let the computer for cool for an hour.
On restarting it the image was perfect but within about 10 minutes I could see the problem developing on it again. When I move the cursor it seems to trigger the problem in parts of the image.
When I reboot the machine and the Toshiba image appears I see thin black vertical stripes through the Toshiba letters.
I asume that this must be a heat sensitive failure in the video card. So this needs to be swapped out?
This means swapping out the motherboard, right?
I have never had this done. Can this be simply done in a way that does not require reloading the programs?
I hope so.
Help with some comments greatly appreciated.
October 21st, 2006 at 10:43 am
Hi, I have a sony vaio pcg-v505ex and I’ve cleaned the lcd screen really well, but I notice fibers or dust under the lcd screen and although it doesn’t effect the performance, its something that wears on me and gets really annoying, just wondering if there is a way to get under a lcd screen and clean the underside of it. thanks
August 2nd, 2006 at 1:27 pm
Just wondering where I could purchase a bulb to be used for testing FL inverters. Is it just easier to grab one out of an old dead laptop (will I run into power issues, or do they generally run around the same voltages?)?
As someone who just bought a FL inverter because I was sure that’s what it was, and now can’t return it, because it was actually the lamp, I’d really appreciate any help, or a point in the right direction…. Thanks