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Where is power to the LCD backlight/inverter come from

Last response: in Laptops & Notebooks
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February 2, 2012 3:18:27 AM

I am trying to diagnose where my LCD backlighting issue is coming from, as all components from the LCD flex connection cable, LCD inverter, LCD & LCD backlight, are in perfect working order, when tested from another unit. It's a Sony Vaio VGN-NR series model VGN-NR350f & both VGA, HDMI external monitor ports are in functional condition still. So I'm completely at a loss for finding the cause to the backlighting issue. Does anyone know where exactly the power to the backlight inverter is delivered from & if this is repairable without having to replace the entire motherboard since the VGA chip is integrated to the board? Thanks for any input on this matter.
February 2, 2012 7:19:24 AM

Your mobo supplies the power to the inverter, have you checked the cable between the mobo and inverter ? If you have checked all this and done a full check with another laptop i would imagine that your MOBO is not giving enought power to the inverter. This could be a small chip on the board seperate from the GPU.

You could go through the rouble of removing the mobo and examine for defects, however it would be difficult to fix. I would price up a new MOBO and see if its worth the hastle of fixing / buying a new laptop.

Hope this helps
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February 2, 2012 10:42:53 PM

Yeah, that's where I'm at with it now. It's only a year old Vaio VGN-NR350f, paid $300 for it & found MOBO for around $175-$225, so it would still be worth replacing, since the chip is integrated to the MOBO & can't be repaired, thanks for the feedback, much appreciated
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February 3, 2012 12:20:38 AM

The power to the inverter is supplied via a switching FET which may be faulty also it is not uncommon for the inverter to be supplied its power via a surface mounted fuse that looks like all the other surface mounted components but slightly larger and normally has an identification of an F on it. I hope that this helps
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February 3, 2012 5:29:11 AM

Thanks, I will research that next, prior to ordering a new MOBO yet, much appreciated
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a c 249 D Laptop
February 3, 2012 8:24:16 PM

Hi :) 

I own a laptop repair company....

What makes you think its not the screen ?

All the best Brett :) 
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February 3, 2012 9:03:29 PM

Ty, I've tested all components from flex cable, LCD, inverter, & backlight, on another fully operational unit. As well as tested the GPU via both VGA & HDMI ports, that is how I'm currently using my laptop in the meantime. Thus illuminating the GPU or LCD as the issue, the screen backlight will make an attempt to illuminate for less than a sec. about every 10 min. It seems that there is some sort of overheating element of some kind. I just don't know what else to check & might as well go ahead & replace the mobo, to be done with it. Would you by chance happen to have a MBX-218 A1747083A for my VGN-NW series Vaio?
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a c 249 D Laptop
February 3, 2012 11:33:12 PM

l3l2YAN said:
Ty, I've tested all components from flex cable, LCD, inverter, & backlight, on another fully operational unit. As well as tested the GPU via both VGA & HDMI ports, that is how I'm currently using my laptop in the meantime. Thus illuminating the GPU or LCD as the issue, the screen backlight will make an attempt to illuminate for less than a sec. about every 10 min. It seems that there is some sort of overheating element of some kind. I just don't know what else to check & might as well go ahead & replace the mobo, to be done with it. Would you by chance happen to have a MBX-218 A1747083A for my VGN-NW series Vaio?



Hi :) 

I am in the UK ...and we buy in mobos to order...to be honest when a lappy needs a mobo with our labour cost added, we tell the customer its rarely worthwhile...unless its a £2000 laptop...

Umm.... HOW precisely did you test the screen itself ?

All the best Brett :) 
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February 11, 2012 2:12:21 AM

It works fine, I can even still use it when I plug the inverter into my other vaio's connector, just run the backlight from that unit. It's just a pain to have to use both units to get one screen to display fully, lol.
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