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Super Technical Question about power inside a MacBook Air

I need to know what voltage the logic board gives out to the keyboard backlight. I know this is very technical but I'm hoping somebody maybe has 1 open or has checked this for themselves in the past. If you look at step 15 you can see what plug I'm talking about that I need a voltage reading for.

MacBook Air 11" Mid 2011 Logic Board Replacement

My MacBook Air keyboard had an issue and when I took it apart I found I needed a new 1. So instead of just getting the same 1 from early 2010 I found out that 2011 and latter are basically the same but have keyboard backlights. So I want to put a backlight in mine but my logic board doesn't have the plug for the back light so I need to know the voltage so I can supply the right power to the backlight from somewhere on my logic board or poss from the battery connector directly next to where it would normally plug in. Thanks in advance for any help.

Update (09/28/2016)

Dan you make a good point.

But, if the keyboard backlight lets just say uses 2 volts to make it a round number and the controller lets you turn it from 1v low to 2v high (full bright) and if I can find an accessible place on the logic board that I can get a steady 1.5v from (give or take) that powers up with the computer and down after shut down.

The only difference is, I won't be able to adjust mine from low to high. My computer without the backlight still uses the exact same battery as the MacBook Air with a backlight so my battery won't die any faster then a computer with a backlight.

I will find the links of the guy on here that did it and post them tonight or tomorrow.

Update (09/29/2016)

Dan,

Did you see my post up above connected to my original post? I understand you don't think it can work and it will be on all the time or kill my battery life.

I've been doing things my whole life that people tell me couldn't be done. Maybe it won't work and I'll burn up my computer or maybe I'll find a way to make it work just because everybody said I can't.

Either way is fine but it's going to be a little harder if I don't know how many volts a backlight takes to power up. I don't need to be able to adjust mine like on the newer models. It just needs to illuminate the keys a little bit so I can see them in a dark room. Like I said if the controller adjusts the brightness by supplying 1v for low and 2v for high I will find a spot that gets 1-1.5v when the comp is turned on and 0 when it's turned off so my keyboards backlight turns on and off with the computer.

Answered! View the answer I have this problem too

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Here's the link to the guy who did it on here. I've found others that have done it by searching google. I just need to know how much voltage the backlight uses so I can find my own spot to use or something somebody else already found.

upgrade keyboard to 2011 model with backlight?

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@jaydeeeze - Jay I've posted a better quality image of the circuit which will answer your questions.

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I believe the keyboard backlight circuit outputs up to around 27V for the LEDs. While theoretically it is totally possible to grab power from a power rail and solder a point onto the backlight connector, is isn't practical. First, you need to grab it from an S0 power rail (fully on state) unless you want the backlight turned on even when the laptops is sleeping or switched off. Most S0 rails are at 1.05, 3.3 or 5 volts which is too low. The LED backlight voltage would be the closest match, but the voltage is too high as it can go up to 50V. Additionally, if for any reason the keyboard backlight short circuits, it will cause a lot of damage to the motherboard. If I were you I would spend a dollar at the store and buy a USB keyboard illuminator!

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Sorry to say if your system's logic board does not offer a connector for the backlight you really can't add it.

Block Image

diagram

Micrel MIC-2292

As you can see there's more to it than powering.

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I know 2 people who have already done it and 1 of them is on here. He posted that he tried it and just had to find a good point on his board to solder a power and ground wire to and got it to work. He did it without the controller but he didn't say where he got his power and ground from. The backlight is just power and ground. All you have to do is find a stable power and ground source on the logic board or somewhere the battery supplies power to and make a power and ground jumper to the 3 positive and 3 negitive wires on the backlight plug. For some reason I can see your picture. It is blury. Can u post a link to it please.

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Jay D would you mind posting a link to your references?

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Jay - Sure I could solder a few wires to the ribbon cable and feed them out though the case to a 9volt battery. But I doubt thats what you want here.

If you tied to the power rail you'd have the backlight on all of the time drawing on the battery. Besides, you'd be cutting down the run time of the system without the power regulation. Which is why you really can't do it cleanly.

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Jay D will be eternally grateful.
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