Macbook Air Early 2015 820-00165 No Backlight

[Constantinos]

Hello everyone.
I am trying to repair a friend's macbook air.
The initial problems were that there was nothing on the display.
The board was water damaged.
After disassembly, I noticed that the fuse was still ok but there was a burned capacitor.
After cleaning the entire board with IPA and replacing the capacitor (L8304 on schematics), I now have the picture without backlight.
The macbook boots and everything works, except for the backlight
There was considerable water damage around the u7701 chip
I haven't repaired macbooks before, but after watching some videos and reading a few articles, I tested for voltage between L7701 and ground. I got 0.0v
I also tested for PPBUS_G3H and found 8.58v
I honestly don't know what to do.
Also, I found c7711 looked a bit black, so I tested it and it was shorting to ground on both sides
After removing, the short went away on one of the sides
But still no backlight
I put the capacitor back on as I was unsure if it was the issue
That is now shorting again
Could anyone help me or guide me on what I need to probe/replace?
Many thanks.

[reformatt]

Re: Macbook Air Early 2015 820-00165 No Backlight

Depends where the water got to. Check the LCD connector J8300 closely for burning around the backlight pins 3/4 (on the LCD cable itself and the board connector). Usually I have to change out this connector along with U7701. BTW, check that the backlight pins aren't shorted when the LCD connector is plugged in, had one recently where the connector had also burned internally IN the screen assembly itself. F7700 would be open circuit if that is the case.

If you had liquid damage around U7701, that's an automatic replacement as you get burning etc around pin 5. Note if you are working on the board on the bench, backlight won't be enabled without a display actually connected. You should at least see 8.6V on C7797 if F7700 is ok and display is connected. If that is the case, then U7701 is stuffed as it should be boosted to 25V.

[Constantinos]

Re: Macbook Air Early 2015 820-00165 No Backlight

Depends where the water got to. Check the LCD connector J8300 closely for burning around the backlight pins 3/4 (on the LCD cable itself and the board connector). Usually I have to change out this connector along with U7701. BTW, check that the backlight pins aren't shorted when the LCD connector is plugged in, had one recently where the connector had also burned internally IN the screen assembly itself. F7700 would be open circuit if that is the case.

If you had liquid damage around U7701, that's an automatic replacement as you get burning etc around pin 5. Note if you are working on the board on the bench, backlight won't be enabled without a display actually connected. You should at least see 8.6V on C7797 if F7700 is ok and display is connected. If that is the case, then U7701 is stuffed as it should be boosted to 25V.

Hi mate
Thanks for your message
The connector J8300 looked fine, no burns and the screen ribbon cable connector looked fine, no burns
There was no shorts between the pins and f7700 is working fine (I have continuity)
I'm going to order a u7701 chip and attempt to solder it on (first time doing bga).
What do you recommend for the other cap that I removed them put back on?

[mon2]

Re: Macbook Air Early 2015 820-00165 No Backlight

Remove all power -> check the resistance across C7711. If the resistance is low, the part is shorted and should not be used.

[reformatt]

Re: Macbook Air Early 2015 820-00165 No Backlight

Hi mate

I'm going to order a u7701 chip and attempt to solder it on (first time doing bga).
What do you recommend for the other cap that I removed them put back on?

If it's your first time doing BGA, then order 5 as they're relatively cheap. Very common fault on A1466 and easy to fix. Once the chip is off, check the pads for damage (pins 5, 11, 16 most common as these pull the most current). In some cases I've had to run jumpers as the pad is often wiped out.

That cap is across PP5V_S0, so I'm surprised it boots if that line is shorted. Normally liquid damage in this area the IC comes off, and any components where the end caps discoloured/black get removed and swapped with those off a donor. Don't bother reballing a donor IC.

[Constantinos]

Re: Macbook Air Early 2015 820-00165 No Backlight

If it's your first time doing BGA, then order 5 as they're relatively cheap. Very common fault on A1466 and easy to fix. Once the chip is off, check the pads for damage (pins 5, 11, 16 most common as these pull the most current). In some cases I've had to run jumpers as the pad is often wiped out.

That cap is across PP5V_S0, so I'm surprised it boots if that line is shorted. Normally liquid damage in this area the IC comes off, and any components where the end caps discoloured/black get removed and swapped with those off a donor. Don't bother reballing a donor IC.

Indeed, most of the caps around that area were quite black, but they mostly cleaned up
I will test c7711 and let you know

[Constantinos]

Re: Macbook Air Early 2015 820-00165 No Backlight

Hello everyone.
Tested a few things, found stable 3.30v to pin 2 of q7706
With regards to c7797, when the laptop is turned on, the voltage slowly increases until it gets to 1.55v, then slowly decreases back to 0v
What does this mean?

[Constantinos]

Re: Macbook Air Early 2015 820-00165 No Backlight

Also, should let you know, the apple logo on the back of the screen does not light up either. Not sure if this is related or not.

[reformatt]

Re: Macbook Air Early 2015 820-00165 No Backlight

If the backlight is enabled, you should have 8.6V on the output of Q7706 so 1.5V is too low. It gets boosted to 25V via L7701/D7701/IC7701.

Apple logo is just an opening on the lid and just allows the backlight to shine through.

[Constantinos]

Re: Macbook Air Early 2015 820-00165 No Backlight

I received the u7701 chip today, and I'm going to attempt to replace it over the next few days (when I have time)
Because I've never done BGA chips before and this chip is tiny, can anyone give any tips.

[reformatt]

Re: Macbook Air Early 2015 820-00165 No Backlight

You need to work out first what temperature and air flow works best for your hot air station. This varies from board to board, your station, and the nozzle you use. This is something that takes a bit of practice, so it's best to work on some donor boards first. These boards require a lot more heat than the newer T1/T2/Mx boards as they are much thicker.

For this BGA, I pre-heat the board first with hot air for about 20 secs. Apply a small dab of no-clean flux on the pads, then line up the chip (correctly orientated) in the approx right position relative to the pads, and hold with tweezers. Apply a small burst of heat to get it to 'stick' into place. Release tweezers (chip should stay in place), then apply your heat proper. Solder should melt and pull the chip onto the pads. Once it moves, you give it a slight nudge to see if it pulls back into position.

[mcplslg123]

Re: Macbook Air Early 2015 820-00165 No Backlight

Hmm, as per post#1,OP claims he replaced L8304 with a capacitor and thats a coil.

[reformatt]

Re: Macbook Air Early 2015 820-00165 No Backlight

Thought that was a typo! OP, could it be that you've replaced an inductor with a cap? Can't tell from the original post as that is obscured by the LCD connector flap.

If that 3V is missing, then the display won't be detected and backlight won't be enabled. Sounds you are on the money as he wasn't getting 8.6V.

[Constantinos]

Re: Macbook Air Early 2015 820-00165 No Backlight

Hmm, as per post#1,OP claims he replaced L8304 with a capacitor and thats a coil.

Hello
It was a typo unfortunately, I just found what component it was from the schematic and I ordered it.

[Constantinos]

Re: Macbook Air Early 2015 820-00165 No Backlight

Hi everyone
I’m in the process of replacing the u7701 chip
Just wanted to let everyone know, after removing the chip, I now have over 8 volts on l7701
I’m going to try and put the new chip on now
Wish me luck!

[Constantinos]

Re: Macbook Air Early 2015 820-00165 No Backlight

So, replacing the chip was a success!
The laptop backlight now works perfectly.
Unfortunately, after using it for a day or two, the keyboard backlight suddenly stopped working.
I have tried cleaning the connector, disabling the light setting in settings and an SMC reset, all to no avail.
Any suggestions?

[reformatt]

Re: Macbook Air Early 2015 820-00165 No Backlight

You can vary the brightness of the keyboard backlight by pressing F5/F6. These only work when the ambient light is low enough, so I just my finger over the screen camera area (where the sensor resides) to test it. So confirm that you get this first before tackling the electronics.

[Constantinos]

Re: Macbook Air Early 2015 820-00165 No Backlight

You can vary the brightness of the keyboard backlight by pressing F5/F6. These only work when the ambient light is low enough, so I just my finger over the screen camera area (where the sensor resides) to test it. So confirm that you get this first before tackling the electronics.

Already tested this, to no avail
Still no lights on the keys

[reformatt]

Re: Macbook Air Early 2015 820-00165 No Backlight

As the MAC was originally water damaged (likely a spillage through the keyboard), check for a short on the keyboard backlight connector (or try another KB backlight - they are pretty cheap). Then check operation of U7750.

[Constantinos]

Re: Macbook Air Early 2015 820-00165 No Backlight

Hi everyone
Forgot to finish off this thread.
The keyboard backlight not working was merely due to the ribbon cable becoming too fragile after inserting/removing it too many times.
I replaced it and now everything works perfectly.
Thank you to everyone for their help