I’ve replaced the broken laptop screen. When I start the laptop the screen flashes and then it goes dark.
A kid broke the screen on a Presarion 900 laptop. I found a used spare one. I’ve replaced the screen 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 voltage?
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.
If the same problem appears on two different screens, probably you have a faild inverter board unless the backlight bulb on the old screen is broken and that’s the reason why the screen is dark.
Where did you test the voltage? On the exit from the inverter board? I think you cannot get accurate readings without a good working backlight bulb attached to the inverter. I believe if the inverter board is not loaded, it will not output high AC voltage. That’s why the best way to test the inverter board is replacing it with a known good one or connecting a good know backlight lamp.
You are right, the output voltage should be much higher than 5 AV volts and there is no super voltage multiplier inside the screen. Low voltage DC power converts into high voltage AC inside the inverter board.
I’ve been searching for a good guide which shows how to test the screen inverter board with a voltmeter but haven’t found it yet. If you find one, please let me know.
February 12th, 2007 at 6:29 am
Hi, thanks for answering. Do you think that if I make a little cut on the wires that connect the inverter to the screen i could get a more accurate reading?
For now, these are the only ways to test it: 1. make those cuts or 2. buy an inverter. I don´t have one around and were I live this are hard to find (central america
) so I talked with the company that sold me the screen on ebay and they say they can sell me the inverter for around 25$.
February 12th, 2007 at 6:43 am
By the way,
I’ve made some tests with the screen attached to the inverter board. Without cutting ofcourse. I simply connected the inverter, and flipped it just a little enough to place the tester in place over the white connector were the HV cable is attached, right behind the contacts. Even there with the screen attached, I’m still getting the 3-5 AC Volts reading. Something weird happened in 1 of the readings: it went from 0.35 AC Volts to 3 V then to 40 V then to 0.35 V and then finally to 3 – 5 Volts. It only got stable at the 3 -5 V reading. It never get stable at that 40 V reading and never got higher that that.
February 13th, 2007 at 7:31 pm
Luiguiv,
as I mentioned before I don’t think that testing with a voltmeter is accurate. Yes, you can test voltage with the backlight bulb attached to the inverter, but what if the bulb is bad and the inverter is not loaded properly? Maybe inverter will not output needed high voltage AC power in this case?
I believe when you have a good working backlight bulb attached to a good working inverter board, it puts out a few hundred volts AC. Not sure how much exactly.
I think you’ll have to buy a good working inverter, hopefully it will fix your problem.
February 27th, 2007 at 3:28 pm
Luiguiv,
i got the same issue you got. was wondering if u
got it fixed..and if u did how u got it done
thanz
March 1st, 2007 at 5:24 pm
I have two Dell Latitude C640s. One is a 2.2Ghz with a WXGA display and the other is 2.0Ghz with the WXGA+ display.
I’m getting rid of the slower one but would like to take advantage of the higher resolution. Would it work if I just swapped the displays?
March 4th, 2007 at 7:26 am
Hi, I have a Toshiba M35-S456 laptop with no display. The display has no cracks, breaks, or apparent defects. I bought a parts only M35-S456 that was suppose to have a good display with a bad mainboard, and it didn’t work either.Seller couldn’t say for sure that it worked before, so it could be bad also. My laptop produces an excellent display on an outside VGA monitor. I replaced the inverter board with a known good one and that didn’t help. Holding a flashlight to the screen doesn’t show anything. I was told by a forum, linked to Toshiba’s website, to sell it all on eBay and buy a new because they are so inexpensive now. I’m not opposed to buying a new display if you think it will work. Any thoughts or test I’ve over looked would be greatly appreciated. Thanks Jerry.
March 4th, 2007 at 4:13 pm
update..got a new lcd and inverter.. and we’re back in biz baby
March 5th, 2007 at 6:36 pm
Todd,
I think it will work (never done it myself) but it might be necessary to swap the video harness too.
March 6th, 2007 at 6:52 am
Thanks.
Over the weekend I decided to give it a shot, hoping that if it didn’t work, the worst I could do was kill the display.
Tried the lower resolution one on the other system first and it worked. Then crossed my fingers and tried the other.
Both worked fine. Just unplug and switch.
March 8th, 2007 at 6:50 pm
i got a dell 1504fp monitor for free it had no backlights but you could still see very dim display after reading a few articles i wasn’t to sure if its a bad ccfl light bulb or the inverter it uses 4 ccfls and at $10.00 ea thats alot to waste if it needs a $70.00 inverter then i figured out a way to test the bulbs i had a older dell latitude cs that uses only one ccfl so i uplugged it and plugged in one from the monitor and then powered it up i repeated that for all four and found one bad one i’m going to get one hopefully that will fix it i’ll post my results
March 11th, 2007 at 4:48 pm
Hi
I was recently given a 3 year old Acer laptop by a friend. The screen was sat on so I have to try and fix it. I can’t find the exact same model of screen. Is it possible to just use any screen as long as it has the right dimensions? Or do I need to get a specific match? Thanks
August 22nd, 2007 at 7:29 pm
Hi… I dunno if this thread is still live, but here goes:
Got an Insignia 32″ LCD TV repair job. Narrowed it down to the inverter being naughty. The screen flashes briefly when you turn it on. My flashlight is out of batteries so I dunno if there’s something on the screen. I also plugged in an audio source and still nothing. I unplugged everything but the board with the CPU chip on it and also I left the control ribbons and power for the FL inverter. The FL inverter hums on, makes the light come on briefly, and then I hear a click from something on the board (I think it’s all the inverter boxes making that noise simultaneously), and the thing shuts off.
I think its dead. Occaisonally it did come on and work perfectly but I haven’t seen that happen for a while now.
A new inverter cannot be bought without the screen too…. so its like $3K to replace.
I want to replace the backlight with something more economical, like LEDs.
The real point of my work right now is to see if I can get stuff on the screen without the backlight.
Any ideas?
The FL board is split in two, with two wide ribbons leading from the power board going to each half (these are carrying 12VDC power). There is a 4-wire control ribbon coming from the CPU/main board. I think that does things like send the on/off signal or something.
I want to “trick” it into thinking the backlight is on. How might I do this? I dont think it works when I unplug the control ribbon for the backlight.
Getting a flashlight to test the screen may be a wise idea at this point…
March 25th, 2008 at 11:31 am
I have the same symptom with my Compaq V2000 laptop. The LCD lights up on startup for a few seconds, then goes very dim.
I just discovered that if I go into F8 startup options, then it does not go blank. More significantly, probably, I found that if I set my LCD at its dimmest level, then when I restart, it does not go blank – until I dial up the brightness.
I’m guessing now that this means that it is more likely the bulb/screen than the inverter.
But if anyone has experience with this or a good theory, I’d love to hear it before I dish out for a new screen.
Thanks
May 4th, 2008 at 7:08 pm
Hi,
I have an old Compaq e700 that I am fixing up to give to a friend. The backlight inverter has gone up. The screen goes dark but the writing is still faintly visible. If you tap the close-lid button several times the screen lights back up. From what I’ve read most Compaqs have the inverter in the display. I’ve downloaded the service manual for the e700 and it explains everything EXCEPT how to open the screen bezel. There are two screws in the front at the lower right and left corners. Are those the only ones? I’ve searched for screws hidden by tape but don’t see any signs. If anyone has any advice, I would be very grateful.
Thanks,
Ruth
May 5th, 2008 at 1:51 pm
Ruth,
Here are some tips for taking apart display panel on a Compaq laptop.
May 5th, 2008 at 10:14 pm
Thank you so much. I was able to open the bezel and replace the inverter without doing any damage to the screen. I’ve saved your tutorial. Anyone reading this thread should know that the backlight inverter on a Compaq e700 is located at the lower right hand side of the display panel, above the hinges. You don’t need to remove the entire bezel to get to it. The seal around the screen edge comes up reluctantly, but you can pull it off. The screws in the bottom corners are the only ones you need to remove. There is a screw in the inverter, on the right hand side. I hope this helps someone else. Once more a big “thank you” to Laptop Freak. It’s great to have a resource like this available.
May 8th, 2008 at 12:22 pm
i have a toshiba satalite with a screen issue . at first the screen was comming on , but down in the right hand bottom corner it was turning black , getting progressively larger by the moment . the corner got very hot also. after checking your website ,it seemed as though the inverter was the problem. so , we ordered an inverter and in a few days it came , we put it in .note , .. the laptop will work just fine with an auxillary screen attatched . during boot up after installation of the new inverter , it looked as though the screen was gonna be fine , the graphicks came right up and all was normal . then , the corner started getting black again ,and then lines started comming across the screen , then blank , again . you can see the graphicks if ya look at the screen from a shadowed angle . but no lighted graphics .
May 8th, 2008 at 11:00 pm
Mark,
This sounds like a problem with the screen. If the external monitor works just fine and this problem appears only on the internal screen, apparently you have a faulty LCD screen and it has to be replaced.
May 31st, 2008 at 11:34 am
I have a pavillion dv4000 that was dropped and the screen cracked but the backlight still worked, the screen was replaced but now no backlight, and an external monitor will ONLY work if the lcd cable is disconneted from the motherboard, the lcd cable and inverter were not replaced, connected test light to inverter and that didn’t worked, any suggestions appreciated to what next to test.
June 17th, 2008 at 5:00 pm
My Vaio is set up to never go to standby when plugged in, but the screen turns off after 10 minutes. The problem is sometimes the screen won’t come back on. I have to hold the on/off button down for 5 seconds so it turns completely off, then turn it back on.
Also, when unplugged it is set to go on standby after a few minutes and sometimes it won’t go into standby like it’s supposed to.