Inverted LCD brightness problem

Hi, i recently bought second hand laptop, previous owner told me it had replaced the lcd screen, when i adjust the brightness by combination of FN and F6 or F7 it goes opposite way, when i adjust it in Windows it goes opposite way too, the worst is that in different power settings modes when i run on battery when screen supposed to safe battery life and dim and it goes brighter instead , i suspect reversed polarity? Have you ever had similar problem? How to deal with it? Maybe it is broken inverter? I am running Win 7 64 Ultimate, Laptop is Toshiba C660 with GMA 4500M GPU, Generic PnP monitor, screen id Monitor\AUO20EC, Manufacturer B156XW02 V0 , i bought it for my mum as a gift, going to upgrade CPU now, but this screen problem is really annoying. Please help.Kind regards.Chris

 

I ran into your thread by searching for brightness problem so I'm not knowledgeable but on the link below someone says it can be done by changing the polarizing film.
Dunno why someone would do this on purpose but looks like it's hardware and your previous owner did something wrong :/ If so then maybe easiest to deal with this would be to buy complete screen with case etc and replace existing one?
Changing LCD display polarity - [H]ard|Forum

 

i have read it before,it doesn't really help, they don't talk about laptop lcds. I thought maybe somebody had simiar problem after screen replacement?

 

Well maybe you better ask on electronic forums where people specialize in this stuff. If they confirm it's the inverter responsible for the signal of brightness level (to me logically it is) then u can buy it off ebay and replace it as you're going to take the machine apart anyway to upgrade cpu.
or maybe he just connected t it the other way ...i think it wasn't possible in the ones I messed with but who knows

Before that did you check in say any portable OS like linux if the problem persists ?

toshiba c660 inverter in Computers/Tablets & Networking | eBay

 

well if we look up there's more about it. it might be even bad circuit on the mobo but most likely it's the wrong LCD screen panel version as people say on different forums
"The bios does not have the correct brightness table information to properly control the backlight"

new lcd reversed brightness problem - Google Search

and this thread below..maybe don't even start reading it. that guy replaced EVERYTHING in the laptop and still had that problem hahaha. so you were warned !!
http://hardforum.com/showthread.php?t=1388108

how trustworthy the seller seems to be ? I woulnd't be suprised that he could have the problem long ago, replaced the screen which didn't solve the problem and then sold it.

 

Its just an incompatible screen, primarily for an HP laptop, the correct replacement will cost you around 50 bux, why do it, im sure its bright enough to get by.