Home
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 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.
January 13th, 2011 at 9:55 am
Robert,
It’s hard to tell what is causing the problem because:
1. The problem is intermittent.
2. Inverter and backlight lamp have very similar failure symptoms (the screen light goes off).
If you don’t have spare parts to test, you’ll have to guess.
1. Try reseating cable connections gain. Make sure the LCD cable has some slack.
2. Try replacing the inverter board first.
January 12th, 2011 at 1:45 pm
Hello.
The Laptop I am working on is a HP Pavillion6000 (dv6500). I decided to take a look at It for a friend and save her some money on repairs(She was given an estimate of $140 USD to replace the backlight
) The issue was a barely visible screen shortly after Startup. I knew the Laptop Itself was ok as far as the Graphics/Mobo, ect, because the external video ports worked with external monitors.
I did a search online to find some leads but to no avail at the time. Read everything from Heat issues, battery issues ect. So, I had basically opened It up to troubleshoot and see where the issue might be. I looked over the wiring/cables and such and all seemed well. Plugged It in and started. The screen now worked and the issue went away. I tried to make the issue happen again to narrow down where It might lye without success. Since It was working and I couldn’t repeat the problem, I Put It all back together and sent It back.
Now, This was about 4 months ago and all has worked well since. Recently, The same issue appeared. The screen shows for a few seconds or minute before It goes dark again. Here I am again doing the same thing.
I personally believe It’s the inverter or the wires/connection(pink & white) from the inverter to the back light.
I’ll send the laptop back again in working condition until/if the issue happens again. It would assist me and maybe others who read this in replacing parts if anyone could answer if a backlight or inverter is able to work/not work/work/notwork, ect. I would tend to think of a backlight as a blown bulb and that’s It. No light ever again. Inverter maybe like a short. a few seconds or minutes… OK. Broke. A few months? lol I hope this might help anyone, And thanks in advance for any input. I’ll try to check back.
January 5th, 2011 at 10:59 am
sourav,
I was going to ask the same question.
How?
I didn’t have time to buy a real compass and experiment with it.
January 5th, 2011 at 10:57 am
Hi Jerry – a compass? how?
December 7th, 2010 at 5:02 am
Jamie is quite right.
With no screen attached the inverter kicks in for a second then stops.
Why buy a meter?
A compass works perfectly well for this job.
November 23rd, 2010 at 3:54 pm
Just a point on the inverter test above and just a hunch but if the backlight has gone then it wont be pulling a current so i would guess the inverter would not be emitting a freqeuncy, so really in teory doesnt this inverter test only work and give a reading if the backlight is ok, would really like to know this might just have to buy a meter to test Hz and test the inverter without a backlight plugged in
November 1st, 2010 at 6:30 am
This “tester” is useless. If the inverter is good and the light in the screen is bad that’s the only situation where this tester would be 100% right. If you don’t get an inverter is OK light on the tester, well then what? I mean is it the inverter bad or is the motherboard not supplying power to the inverter? It won’t tell you that. It will just let you test a light in the screen and see if the inverter is working.
If you get an inverter light then you know where the problem is, if you don’t then you are still in the dark.