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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.
December 1st, 2011 at 12:46 pm
@ Angelo,
Test your laptop with an external monitor. Do you see same problem on the external image? If yes, probably this is graphics card related failure.
Normally, a bad screen wouldn’t affect Windows functionality.
November 26th, 2011 at 9:56 am
Hi,
I’ve been having problems with Sony VGN-FE590P.
Screen has vertical, mostly red, lines on start up and later. Altogether picture is bad throughout.
The weird thing though is that the Windows crashes as well. The safe mode runs (with the error) but the full driven system crashes upon start up.
I tried to re-install the system but during the recovery process itself the screen error was present as well. That meant, I suppose, it wasn’t the Windows.
Because of crashing I suspect the motherboard or something big like that.
I wanted to open the laptop to check for a visible damage so that’s what I’m doing now.
Is it possible that the screen returns some feedback and Windows crash upon a failure to receive.
Do you have any advice how to test for the problem?
Thanks,
Angelo
April 27th, 2011 at 7:53 am
I have a HP laptop It start fliking then the screen stop. I test external It work well and I try to check the cables I have my friend have the same and I try the hole LCD on his laptop it work well so,
1- Is the connector is the problem
2- or the led switch
thanks any help
March 18th, 2011 at 10:25 am
jeff,
Cannot tell the exact voltage. 10-11 volts sounds about right.
The laptop has to have some kind of lid close switch. If it doesn’t have a good old physical button somewhere close to the hinge, most likely the laptop has a magnetic lid switch – a piece of small magnet inside the display panel activates the switch which is hidden under the palmrest.
March 18th, 2011 at 10:21 am
Jeff,
It’s hard to tell what is causing the problem but it’s possible you have a bad backlight lamp inside the LCD screen.
The only way to find out what is bad is testing the laptop with another known good screen.
March 17th, 2011 at 9:44 am
HI, I have a Acer Aspire 5335….With inverter #19.21030.m46
I have tested the Back-light bulb and it works fine…
The laptop also works fine with a external monitor…
Two questions.
What is the input voltage to the inverter?
I tested it and got two reading…11.01 and 10.38 volts..DC off pin 1 to ground.
Does the laptop have a lid switch? I cant find one and there is no settings in the bios to adjust.
March 17th, 2011 at 9:41 am
I have a Sony VAIO VGN-AX570G I had the LCD screen replaced 2 years ago but recently it started to flicker until finally the backlight stopped working. So I had the power inverter replaced YESTERDAY with an authentic Sony inverter. At first it was running perfect for several hours.
Then I restarted it and t flickered but stabilized. But now (today) the backlight won’t come on. What is wrong it? It is so frustrating because this is the 2nd time within 5 years that I replaced the LCD screen. I never dropped, banged it, nothing.
Please advise, thank you.
March 13th, 2011 at 10:35 am
Marie,
It’s hard to tell.
There is a chance the new inverter is defective. It’s not likely but possible. Did you buy it from an official Sony reseller? Can you exchange this inverter under warranty?
If it’s not the inverter, probably you have a faulty backlight lamp inside the LCD screen. In this case you’ll have to replace the screen.
I really cannot tell which one is causing the problem without testing the laptop with another known good inverter or backlight lamp.
I don’t know whee you buy spare parts, but some new replacement screens available here.
March 13th, 2011 at 6:19 am
I have a Sony VAIO VGN-AX570G I had the LCD screen replaced 2 years ago but recently it started to flicker until finally the backlight stopped working. So I had the power inverter replaced YESTERDAY with an authentic Sony inverter. At first it was running perfect for several hours.
Then I restarted it and t flickered but stabilized. But now (today) the backlight won’t come on. What is wrong it? It is so frustrating because this is the 2nd time within 5 years that I replaced the LCD screen. I never dropped, banged it, nothing.
Please advise, thank you.
March 11th, 2011 at 12:14 pm
HI, I have a Acer Aspire 5335….With inverter #19.21030.m46
I have tested the Back-light bulb and it works fine…
The laptop also works fine with a external monitor…
Two questions.
What is the input voltage to the inverter?
I tested it and got two reading…11.01 and 10.38 volts..DC off pin 1 to ground.
Does the laptop have a lid switch? I cant find one and there is no settings in the bios to adjust.