Bad Inverter or backlight?

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shrapnel_indie

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Would a Bad Inverter cause a laptop screen to flicker and look blank? Or am I looking more at a bad back-light? Is there an easy way to tell which is which? I'd hate to buy a new inverter and it turns out to be the back-light.

Background:

I have a Lenovo 3000 n100 that when I first looked at it for a friend that it would light up for a second, off color, (kind of amber) when you first opened the lid, and then it would go "blank."

I disassembled it to make sure the connections were good, and they are. I noticed when I held it just right, if what was displayed was light enough in color (i.e. white) I could see it was present on the screen. It currently will sometimes flicker on for a moment, off color, when you would be expecting it to change screen modes, or on start-up.

It also works fine using an external monitor, other than seeing a post or splash screen. (It's apparently configured for the flash screen, displaying the Lenevo logo.)
 

prelude2250

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Inverters and bad backlights can be hard to diagnose without just replacing the parts. If you have a multi-meter that can read in hertz then you can hold the ends up to the inverter board and see if you get a reading. a good inverter will give you a reading of about 25-90 on the multimeter. Apparently inverters are the only things in laptops that use such high frequency currents. If you don't, I'd suggest just buying a replacement inverter and seeing if that fixes it. That will be the cheapest and easiest 1st step. Changing a screen can cost you $85-$150, and changing the backlight isn't for the faint of heart. They are so easy to break.
 

prelude2250

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Inverters and bad backlights can be hard to diagnose without just replacing the parts. If you have a multi-meter that can read in hertz then you can hold the ends up to the inverter board and see if you get a reading. a good inverter will give you a reading of about 25-90 on the multimeter. Apparently inverters are the only things in laptops that use such high frequency currents. If you don't, I'd suggest just buying a replacement inverter and seeing if that fixes it. That will be the cheapest and easiest 1st step. Changing a screen can cost you $85-$150, and changing the backlight isn't for the faint of heart. They are so easy to break.
 

shrapnel_indie

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Unfortunately I don't have a DMM capable of measuring frequency and I don't have access to a scope either. :(

I know I've asked this question elsewhere and was informed by someone that they felt it was the backlight because in their experience the backlight was the more common failure and they suggested placing pressure on the inverter board. They however failed to inform me what to interpret the results of such a test.

Thanks for the input, I think that is where I'll start then. I don't think replacing the LCD assembly will be too difficult as long as I am careful if it comes down to it.
 
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