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.
July 22nd, 2007 at 1:30 am
If you need to replace inverter, i wrote a walkthru. here:
http://www.hk3d.com/temp/InverterReplacement.pdf
April 8th, 2007 at 6:50 pm
There are horizontal stripes on my laptop lcd screen and I got them after I put a burned cd to listen to music. The stripes are pink on white background and green on black or other dark backgrounds. How do I get rid of it?
February 16th, 2007 at 7:50 am
thank you very much,
i followed option one but the pins to make the metal connectors stay inside the plastic piece were in different locations so it wouldn’t hold.
instead i cut off the connector with the wires from the old screen and spliced them and twisted them to the wires from the new screen and all is working well
once again thank you for your prompt response i wasn’t expecting a response for a while.
Boruch
February 15th, 2007 at 10:58 pm
Boruch,
It’s difficult and very time consuming because wires are soldered to the backlight bulb. You’ll have to disassemble the screen, remove the backlight bulb, unsolder old wires and replace them. I wouldn’t go this route because you can easily damage the screen.
It’s possible but do you know witch one to buy? I don’t. I’ll have to have a bunch of different inverters to find out witch one will work with your screen.
I think you can try these:
1. You have two wires coming from the screen. Both wires have a small female connector on the end and they are secured inside the white connector. You can try releasing both wires from one connector and plug them into the other. It’s difficult but I think possible.
2. Cut off both connectors and solder the connector you need to the screen you need. It should work but you cannot return the screen back to the seller if you have to.
February 15th, 2007 at 12:12 pm
I have a toshiba a45-s120 on which the screen cracked.
the original screen was model LQ150X1lHC3 B
the replacement screen i bought is model LP150X06
my only issue is that the plug to go into the inverter is different between the two
do i need to by a new inverter? can i just splice it? if i open up the screens will i be able to switch the wires?
if i have to get a new inverter how do i find out which model to get?
Thankyou
February 11th, 2007 at 10:03 pm
Luiguiv,
I think you might have a failed inverter board. I’ve published your question and some suggestions here. Hopefully somebody else can give you a better advice on testing the screen inverter.
February 10th, 2007 at 9:28 pm
Hi. I’m kinda having the same problem with a presario 900. A kid broke the screen so, I found a used spare one at ebay. I’v replaced it on the laptop and when i start it light flashes for 1 second at the “COMPAQ” logo and then it goes dark. I can still see the image in the dark but no light. I’m thinking about a bad inverter. I placed back the broken screen and it doesn´t light either. I thought maybe the new screen has a problem but if the broken one doesn´t lights i guess is the inverter the real problem. So, I got my multimeter and tested the output voltage; it is 3 to 4 maybe 5 AC volts tops. I’m I right about the bad inverter looking at this voltages?
As far as I know, voltage should be “high” not under 10s right? and i don´t think that the screen has a super voltage multiplier inside that boosts the 4V to over 100…right?
First I thought maybe I got scammed with the screen but after seeing this output I guess the problem is my inverter.
Any help is welcome.
February 6th, 2007 at 2:16 pm
Neil,
Most likely they are wireless card antennas. I guess the white wire goes to the main connector on the wireless card and gray one to the auxiliary connector. If you don’t have any internal wireless card installed, route the wires to the wireless card slot on the motherboard and fix them in that area to the motherboard with a sticky tape. Make sure contacts not touching the motherboard.
February 6th, 2007 at 2:07 pm
Hi there, ok sir to begin with thank you for your help, hopfully i can resolve this problem. I have a (Gateway laptop model# M305crv). recently i was replacing the internal male peice of the power adapter, anyways while I was taking the laptop apart, I wasent paying close enough attention I guess, So while taking the lcd screen off there were 2 wires “black and grey” which while in the prosess had come undone or removed, I can’t for the love of it figure out were those 2 lcd screen wires go when I putting everything back together. Any help or information would be greatly appriciated!!!!
January 26th, 2007 at 6:29 pm
Easiest way: Hover O-Scope probe around the inverter t-formers. U should be able to detect the leaking high voltage current.
January 19th, 2007 at 10:24 am
Frank A. Madero,
That was a typo. Thank you, I fixed it.
I changed “FL inverter bulb” to “backlight bulb”. I have a few working backlight bulbs I pulled form broken screens and use them for test.
January 19th, 2007 at 10:05 am
In your article above you say “Usually, when I have a problem with the backlight, I unplug the screen and connect my test FL inverter bulb.”, what is a test FL inverter bulb and how can I aquire/make one?
-thanks
January 15th, 2007 at 8:07 am
Hey Laptop Freak, Ok so I recieved the new inverter on Friday and installed it and the monitor lit up perfectly no lines – no degrades anywhere, it looks great, running perfect has been running all this weekend. And I put it to the ultimate test I let my 13 year old daughter surf the net with it.. (lol) but at any rate after looking at the inverter and compairing it to the other Sharp screen that local computer store put in who shall remain nameless but one that I will NEVER refer anyone to.. After looking it over HE DID in fact remove my orginal inverter and replace it with a dead one.. So I guess that is my lession to be learned get it in writting what they are going to be doing to your laptop.. I just knew that he changed something but I couldn’t prove it, because like I said when it went in there it lit just fine and when I picked it up (nothing) even with the new Toshiba screen replaced.. Well I just want to THANK YOU very much for ALL YOUR knowledge/help, it is truly apprciated..keep up the great work.
January 11th, 2007 at 7:42 pm
there is no way to plug the lcd into the mother board with out the inverter the inverter has to seperate types of connectors on each end. so you can not bypass it
January 11th, 2007 at 3:06 pm
okie1211,
So, the laptop boots fine with an external monitor when the inverter board is disconnected and will not boot when the inverter is connected. Sounds like a bad inverter?
Here’s one more thing to try, just to make sure that the problem is related to the inverter. Plug the video cable into the motherboard, plug the other end into the LCD and DON’T connect the inverter board. The laptop still boots fine without inverter connected? The laptop boots to the desktop without any problem (the image on the screen will be very dim)?
January 11th, 2007 at 2:43 am
that is what i’ve done, on the hp laptop the only thing connecting the mother board to the lcd is the inverter board. when this is left connected it will not work at all. when i disconnect it, it works.
January 10th, 2007 at 8:29 pm
Nina,
I’m pretty sure that before you took the laptop to a repair shop you had only a cracked screen. I’m not really sure what is going on now. I don’t think the repair man installed his inverter and left it in there, it’s not a cheap part that you just give away for free.
Try this. Even if you have a cracked screen with bad FL inverter, the laptop still should work fine with an external monitor. Connect an external monitor to the VGA port and start the laptop. Will it work fine with the external monitor? If the external monitor as black as the LCD, a new inverter board will not help you. There is something else wrong with the computer.
January 10th, 2007 at 10:53 am
Well i did remove the LCD inverter and sure enough i was able to attach an external monitor and get something. Now i just have to figure out what to do next. i get a HP logo screen with 4 different options none of which work. but thats for another day, at least i found out why the screen wouldn’t work.
January 10th, 2007 at 7:27 am
Thank you for replying so soon. To answer your question. Yes the LCD screen was still as bright as before just with a crack in it (no other problems or defects was working great). And here is the part that is killing me. When it left me at the repair facility it still lit up. Its when I picked it up this past Friday, is when the screen was black upon booting up.. SO that is why in my mind once I REMOVED the SHARP screen that he (repair man)had put in and I replaced it with an orginal used Toshiba Screen and it still did not change from the black screen. That is when I thought he must have done something else to this unit, I mean if nothing else the sceeen should atleast light like before. So the only other thing I could think of is maybe he changed the inverter to make it fit the other screen or maybe WELL WHO KNOWS, all I know is it was a simple repair and (AFTER have my computer for a FULL month)all he could say was to me was, “oo hunny you should just buy a new one”… I have no way of proving he took or changed the inverter at least I dont think I do. All I know is that now my screen doesn’t even light, so I did order an NEW FL inverter for my model with the hopes it will fix the problem. I will be replacing it myself and was wondering if you could give me any tips on what I should look for or be doing when I replace it. thank you again for you help.
January 9th, 2007 at 7:04 pm
Okie1211,
Not sure if the inverter can cause such problem, doubt it. Here’s what you can try. Disconnect the video cable from the motherboard and test the laptop just with an external monitor. If you still have intermittent startup problems, it has nothing to do with the inveterate board.
January 9th, 2007 at 5:18 pm
Nina,
You dropped the laptop and after that you still can see the desktop (I assume it’s as bright as before) but there is a crack running down the screen, right? This tells me that there is nothing wrong with the FL inverter, it’s just a cracked LCD. You shouldn’t replace the inverter board.
So you’ve purchased a used LCD from eBay and when you connect it to the laptop it doesn’t work. There is no image and no light, right? Are you sure that the new LCD screen is compatible with your model? Try connecting the old, cracked LCD screen back to the laptop. Are you still getting the backlight? If not, can you see a very faint image on the screen if you look very closely?
January 8th, 2007 at 3:22 pm
hi, i’m having a similar problem and think it might me an inverter issue, could the inverter cause the laptop to not power up also…. when it does power up, the screen is really dim and i can barely make out the hp logo. just trying to rule every thing out. already replaced the motherboard and ac adapter. still nothing. thanks for your help.
January 8th, 2007 at 10:05 am
Hello, my Toshiba Satellite 1905 was dropped and hit the coffee table and upon looking at it you can see the images, (ie icons) but it had a crack running down the screen which appeared distorted, so I thought its got to be the LCD screen. So I ordered a used one of ebay. But in the mean time I took it to a local computer repair company who looked it over and told me they could not repair it. Weird I know… So I recieved my USED LCD from ebay, pick up my computer from the repair man and attempted to repair my LCD myself. I take it home open it up and come to find out that he replace my Toshiba screen with a Sharp. So then I remove the Sharp screen and install the Toshiba screen hoping that would make it work, instead all I get is a black screen nothing on it. The computer boots up fine but no images on the screen.. So my next thought was its goto be the FL inverter.. What should I look at with respect to that?? Is it possible this man removed my Toshiba inverter and replaced it with a Sharp just like he did the LCD screen… or is there something I should try.. My only thought is when my laptop left me it was illuminated, just a crack running thru screen and now I cant even get it to light up. thank you in advance for help
January 5th, 2007 at 5:53 pm
Thank you for the advice
This is the only one I can find on ebay
I bought 2 different inverters on ebay for the 9100
1. did not bolt on and wanted to catch on fire when I tried it
the second is this one
The seller told me he has sold it to other people with a 9100 and it just doesnt bolt on right
I lowereed the brightness and it doesnt get hot anymore
Ill look for another inverter hopefully this one doesnt catch on fire or anything
January 5th, 2007 at 12:41 pm
Matt 21:
I have the same problem with a thinkpad a22e(works good with crt, will shutdown when using lcd). I removed the lcd panel and cable and it still acts the same. Thinking it is a bad motherboard even though it works fine when the CRT only is used. Did you find anything else out about this problem?
January 4th, 2007 at 8:07 pm
Martin,
I think it’s possible that you purchased a wrong FL inverter for your screen. Usually it gets warm but it shouldn’t be hot. Also, you should be able to mount this inverter board the same way as the old one was mounted. At least you know that the problem is fixed and fortunately Dell inverters are not expensive.
January 4th, 2007 at 10:54 am
Thanks you for your advice
I recently bought an inverter for my inspiron 9100 and it fixed the problem
1. The part does not bolt onto my Inspiron 9100 it has to holes for the screws but they don’t line up on my display they are too far apart. Is this the correct part?
I put 1 screw on it to hold it in place for now
2. When plugged in it works fine but it gets real hot probably the same temperature as a fully charged battery while its charging
Is it suppose to heat up and stay that hot?
Will it eventually burn out if it is getting that hot? I don’t want my laptop to catch fire
January 1st, 2007 at 8:09 pm
Lawrence,
If the lines appears only on the laptop LCD screen but not on the external monitor, than I would guess that you have a faulty video cable (less likely) or bad LCD screen (more likely). You can find more help regarding this topic here.
December 31st, 2006 at 12:40 am
my toshiba qosimo started showing coloured horizontal lines all of a sudden at first it was one,then two there are 5 lines,seems like the lines are increasing,when connected to an external monitor it does not shot the lines,what can be wrong
December 28th, 2006 at 8:26 pm
Michael,
You can set the laptop to output video on an external screen, but I don’t think it’s possible to use the laptop LCD screen for a desktop PC.