Comments on: Any ideas on how to properly test voltage on the LCD inverter input and output?

By: Dave Bolger

Dave Bolger — Sat, 14 Nov 2009 00:47:47 +0000

For testing inverter, check out this link…. it could save you a lot of time and hassle!!http://www.fonerbooks.com/test.htm

By: Luis Pedro

Luis Pedro — Wed, 03 Jun 2009 21:08:19 +0000

Hey Everybody,

I had the same issue about measuring the inverter output, but I found out that if you measure in paralell to the inverter exit you will get no reading, I’m guessing the inverter can’t take much Amps, I tried measuring on a working laptop and when I tried to measure the voltage the whole screen whent dim, I had to shut it down and then turn it back on to have the screen light up ok.

On the bad laptop I just bought the backlight that I’m guessing is what’s wrong with it.

hope this helps anyone!

By: Andrew

Andrew — Tue, 31 Mar 2009 17:09:55 +0000

Hi,
I trapped one of the 7 wires running from my laptop motherboard to the inverter and it shorted out, my screen is on but with a dim image using AC power. I checked the inverter was working with an old CCFL. I got a bright picture back by touching Pin1 to Pin4 but on battery is was back to a dim picture (Accidently touching Pin1 to Pin3 made a spark and turned the screen off completely) Turning the notebook on I am now back to a dim picture, I took readings before and after the event -
Before (Dim Picture) Pin1 7.12v; Pin2 7.12v; Pin3 0v; Pin4 0v; Pin5 2.49v; Pin6 2.5v; Pin7 2.53v
Now (Very Dim Picture) Pin1 1.94v; Pin2 1.94v; Pin3 0v; Pin4 0v; Pin5 2.49v; Pin6 2.5v; Pin7 2.27v
Given that my screen and inverter are OK how can I get my bright picture back, using the keyboard dim keys only make it darker. There is no graphics card it must be built in and I get a perfect picture on an external monitor. Have I upset a setting on the motherboard by trapping the Pin1 wire and if so how can I reset it? Could I shock it back again? If so what pins and voltage would you suggest and how now that the voltage in Pin1 is so low it does nothing when I touch it to Pin4?

By: Kahlil

Kahlil — Fri, 31 Oct 2008 22:25:11 +0000

I’m having backlight issues with a 17″ PowerBook G4. The light went out right after I replaced a bad video cable. OH, cruel irony!

By: Laptop Freak

Laptop Freak — Tue, 08 Jul 2008 04:01:41 +0000

Christian,

The backlight on my laptop LCD lights up..but there is no image

I think you have a problem with the LCD screen. I published your question and some suggestions here: Laptop LCD lights up but there is no image

By: Christian

Christian — Mon, 07 Jul 2008 23:37:56 +0000

I have an interesting problem.
The backlight on my laptop LCD lights up..but there is no image

Even when its Posting (before booting in the OS)
there is no image.

HOWEVER if i put pressure on a corner of the lcd, the image shows up.

Is it a bad Inverter or video cable or other?

By: Laptop Freak

Laptop Freak — Wed, 18 Jun 2008 05:22:31 +0000

Thank you Derek,

if you want a test backlight bulb, you can just get those CCFL light kit for case modding on ebay. they are cheap, like 5 dollars i think. you might need to reharness your connections to make them compatible however.

That’s a good point and the only reliable method to find out what is causing the problem, the backlight lamp or the inverter.

By: Derek

Derek — Wed, 18 Jun 2008 04:32:51 +0000

if you want a test backlight bulb, you can just get those CCFL light kit for case modding on ebay. they are cheap, like 5 dollars i think. you might need to reharness your connections to make them compatible however.

By: Laptop Freak

Laptop Freak — Thu, 01 May 2008 19:56:51 +0000

Mark,

The lcd lights up bright but have no images. An external monitor works fine when hooked up. Could this be an inverter problem or a motherboard problem.

If the screen lights up, this is not an inverter problem. This first think to check would be the video cable. Try reseating the video cable on the back of the LCD screen. It’s possible the cable got loose. If reseating the video cable doesn’t help, I would probably try replacing the cable.
Could this be a motherboard problem? Yes, but I would play with the video cable first.
By the way, this could be a LCD problem too.

By: Mark

Mark — Sat, 26 Apr 2008 22:54:23 +0000

I have a Toshiba a45-s150 with LCD problem. The lcd lights up bright but have no images. An external monitor works fine when hooked up. Could this be an inverter problem or a motherboard problem. The video card is intergrated.

Thanks
Mark