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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.
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July 21st, 2009 at 4:36 pm
I have a suggestion for you on a temporary “snooping” into inverter errors (working/not working) situations. I used an old non-working inverter and put my probes into the high voltage end of the inverter while it was not plugged into anything. I put my Amprobe 33XR-A on ac voltage and on an hp laptop, I read nearly 1 volt of ac. I then switched it over to Hz position and read 54 KHz! So, there! As a former RADAR tech in Uncle Sam’s Air Force, I saved a lot of time to research that! Tear apart an old inverter board and make some probes to plug into the meter and use the mini transformer as a probe or as the ham guys used to call it a grid/dip meter to sniff out RF!
You are welcome!
June 11th, 2009 at 2:33 am
Hi,
Great site, I now have a much better appreciation of my problem. But before I pull apart the wrong things, I thought I’d get an expert opinion… On my fiancee’s Acer travelmate 2420 the backlight fails after a short while (< 1 minute). It can be turned back on with the close lid button but fails soon after (increasingly shorter periods). This only seems to be an issue under AC power. Everything works fine under batteries. Any suggestions?
Thanks