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Is it possible to test laptop screen inverters with a regular multimeter? I was asking myself exactly the same question many times before until I found this article published by Morris Rosenthal. Apparently, you can test inverters with a multimeter but you have to have the right one, with frequency rated at least 50KHz.
my $20 meter failed to register anything! So I borrowed a better meter from my neighbor, a Fluke 110 true RMS meter. The Fluke specs show it’s rated to 50KHz, which turned out to be critical in the inverter test application.
I’m not sure how accurate this test is, so I will probably find a Fluke multimeter and try it myself. If this test works 100%, it will be very helpful to me.
By the way, some of you may ask what a screen inverter is and where it’s located inside a laptop? I’ll try to answer in a few words. The inverter board is a power supply for the LCD screen and it powers up the backlight lamp (CCFL) inside the LCD screen. When inverter fails, the LCD screen remains dark even after your turn on the laptop. You still can use the laptop with an external monitor attached to the VGA port but not with the internal screen. The image on the laptop screen will be very dark, almost invisible. The inverter board is located inside the display panel and in most laptops you’ll find the inverter board located right below the LCD screen.
The image below explains how the inverter board is connected to other components inside your laptop. You’ll find more information in this article.
Here’s how you can test the inverter board using a spare backlight lamp.
Basically, you unplug the LCD screen from the inverter and plug in a known good backlight instead. If your test backlight lamp doesn’t light up, most likely there is a problem with the inverter board.
If you plat to test more than one LCD screen, you mgith consider buying this CCFL bulb and inverter tester designed by LCDParts.net. You can find this tester here.
Finally we have the LCD Screen Tester available (LST01 is including a 12V DC Adapter) after months of experiment with many different types of LCD screens. No more guess works! This custom built equipment can help you isolate problem between CCFL Backlight Lamp and Inverter in seconds.
March 16th, 2009 at 10:23 pm
I have a VAIO PCG-K33F with a problem I can’t seem to figure out, and I need help please. This laptop turns on and at first and sometimes, I get image and everything, then after a while, I restart the machine and the VAIO intro screen doesn’t appear but I can hear the system going into windows and initialize, there is light in the LCD lamps but there is no WINDOWS IMAGE coming on, can anyone here tell me what the problem might be? thank you so much
March 7th, 2009 at 1:04 pm
James,
Does it work like that right from the start up? When you turn on the laptop, the Compaq logo appears on the screen. Is it in the center of the screen or in the center of the left half of the screen?
I’m just trying to find out if the video works fine in the BIOS and the problem appears only when Windows loads.
March 6th, 2009 at 7:36 am
My Compaq presario v2000 displays the image in only the left half of the screen, while the right half is completely blank. Haven’t checked with the external monitor though. I suppose its the hinge wiring problem, just a guess. Its not that half the screen content is not displayed. Just that the complete content is displayed in the half portion.
Any idea on this problem?
Steve, did u get it fixed??
February 22nd, 2009 at 8:13 pm
MY COMPAQ PRESARIO V5000 LCD SCREEN SHOWS THE DESKTOP IN TRIPLICATE ON THE SCREEN ABOUT 1/3RD FROM THE LEFT THEN A 2 INCH BLACK STRIP TOP TO BOTTOM THEN STARTS OVER AGAIN. EVERYTHING WORKS FINE ON AN EXTERNAL MONITOR. I CAN USE THE LAPTOP IN THIS CONDITION BUT IT IS HARD TO READ THIS WAY.
IS IT THE SCREEN, INVERTER. VIDEO CARD??
January 20th, 2009 at 10:36 pm
RobMac,
Sounds like a problem with the LCD screen.
When the laptop LCD fails and starts displaying lines, can you force it back to normal if you move/twist/torque the display panel. If you can, probably it’s a bad LCD.
January 19th, 2009 at 8:05 pm
Laptop Tech,
What a great site – but I too have a laptop video problem.
On my Acer LT (3230) LCD I get good video then it fails to vertical lines (I can see video changing in lines) then back to a good picture until it once again fails to vertical lines. At first I thought it was heat related but now unsure. Video is stable on an external (VGA) monitor. I have pulled pushed tapped and poked all cables and reset connectors without resolve. Your council would be very welcome.
Regards RobMac.
January 16th, 2009 at 12:59 am
Thanks for clearing that up… I’ve been working on it for days.
January 15th, 2009 at 10:44 pm
Dominick,
It sounds that you still can see the image on the screen, so you problem is not related to the backlight lamp or inverter board.
From your description I can tell that you have a problem with the LCD screen. You’ll have to either replace the screen or use it as is.
January 15th, 2009 at 10:23 pm
Hello, I have an old dell latitude c640 that runs really well, but the screen has a vertical dark patch coming from the bottom-middle of my screen. It is darkest at that spot and changing the screen brightness works every were except that spot. Is this a backlight or inverter problem? I would attempt to use a voltmeter, but I don’t have one and it would cost just as much to buy one than it would buying another inverter.
January 5th, 2009 at 12:54 pm
: ) Thanks ya, i’ll do just that. Right now the CCFL tube is working properly—although it hasn’t for quite some time (over a year, really). Either it’s at its best state, but failing, or it was a wiring issue all along (irony~~). I’m going to try and see how it works placed back in the LCD this time around, but i’ll still order a new one just to be safe.
Just wish it would’ve been working like this in the first place, but my luck permits things like this happening. : D
Thanks for your help, and for the link to the CCFL buy. : ) Really appreciate it!