820-3435 No power / light

[lebronballer]

Mac Air had a few drops of water spilled on keyboard. I opened it and saw slight corrosion on U7090. So far only cleaned it with a brush and alcohol.

Measuring voltages Here's what i'm seeing:
PPDCIN_G3H is giving me 15v (though it cycles between 14.9 to 15.0)
I also get 15v at the magport and dcin on the board, and also at PP18V5_DCIN_ISOL_R.

I thought those were supposed to be 18.5V?

Also, on PPBUS_G3H i only get 3mV @ R7006 which i think should be 8.6V?

Any ideas where to check next? I'm a beginner, so appreciate all the help.

[piernov]

Re: 820-3435 No power / light

Magsafe2 45W sends out 14.85V as written on the brick.
Check voltage and resistance to ground on L7095.
Check resistance to ground and voltage on both sides of F7140.

[lebronballer]

Re: 820-3435 No power / light

Magsafe2 45W sends out 14.85V as written on the brick.
Check voltage and resistance to ground on L7095.
Check resistance to ground and voltage on both sides of F7140.

Thanks.

On L7095- 0.1mV on both sides, 82.5kohm both sides.
On F7140- I get OL on both sides resistance to ground. And voltage with MagSafe plugged in was 0.7V and continuously dropping.

I also have 14.9v on c7090 /c7091 pin 1.

Does this suggest it's just u7090 that's either bad or not making a connection (must stilll have corrosion)?

[piernov]

Re: 820-3435 No power / light

Confirm that pin 6 and pin 8 of U7090 get 14V. Only then you can suspect something wrong with it.

[lebronballer]

Re: 820-3435 No power / light

Confirm that pin 6 and pin 8 of U7090 get 14V. Only then you can suspect something wrong with it.

Either i cant get the multimeter probes on pin 6/8 or they arent getting a reading, but i do measure 14.9v on both the test points leading to pin 6 and 8 right next to them (P3V42G3H_SHDN_L & PPVIN_G3H_P3V42G3H).

Do you think first try to heat it up to pull it off and clean then put it back, then replace it if that doesn't work?

[MobileXT]

Re: 820-3435 No power / light

Do you have a PP3v42_G3H?

[lebronballer]

Re: 820-3435 No power / light

Do you have a PP3v42_G3H?

Nope, nothing coming out of U7090. I measured PP3v42_G3H at L7095 and got nothing (0.1mV).

[MobileXT]

Re: 820-3435 No power / light

You need to fix your PP3V42_G3h first.

[MobileXT]

Re: 820-3435 No power / light

Nope, nothing coming out of U7090. I measured PP3v42_G3H at L7095 and got nothing (0.1mV).

Also check for shorted on that power rail. IF you don't have shorted then you can replace U7090

[lebronballer]

Re: 820-3435 No power / light

You need to fix your PP3V42_G3h first.

Isn't that originating at U7090? Since i have both the PPVIN_G3H_P3V42G3H & P3V42G3H_SHDN_L coming to the testpoints before pins 6 & 8 there?

[MobileXT]

Re: 820-3435 No power / light

Sorry Check first R7006 and R7005

[MobileXT]

Re: 820-3435 No power / light

Isn't that originating at U7090? Since i have both the PPVIN_G3H_P3V42G3H & P3V42G3H_SHDN_L coming to the testpoints before pins 6 & 8 there?

If you have 14.75V at Pin 6 U7090 replace U7090

[lebronballer]

Re: 820-3435 No power / light

If you have 14.75V at Pin 6 U7090 replace U7090

So i measure 14.9V at the testpoint next to pin 6 U7090. Pin 6 is the one that had corrosion on U7090 and i either dont get a reading on the actual chip, or i cant get the probe right on it so i was using the test point in the image attached.

i have 14.9-15v at R7005. I have ~0.7V at R7006 and it keeps dropping over time (maybe to 0, down to 0.4v now).

[MobileXT]

Re: 820-3435 No power / light

Your U7090 is dead you need to replace the chip

[MobileXT]

Re: 820-3435 No power / light

So i measure 14.9V at the testpoint next to pin 6 U7090. Pin 6 is the one that had corrosion on U7090 and i either dont get a reading on the actual chip, or i cant get the probe right on it so i was using the test point in the image attached.

i have 14.9-15v at R7005. I have ~0.7V at R7006 and it keeps dropping over time (maybe to 0, down to 0.4v now).

Check the resistance should be 10 ohms

[MobileXT]

Re: 820-3435 No power / light

Put your multimeter at Diode Mode and Red on ground and Black at Pin 6 U7090 or PIN 1 at C7091 check if you have shorted.

[lebronballer]

Re: 820-3435 No power / light

Put your multimeter at Diode Mode and Red on ground and Black at Pin 6 U7090 or PIN 1 at C7091 check if you have shorted.

Resistance on the resistors look right.
Pin 1 at c7091 in diode mode shows 0.343v. Can't get a reading on the corroded pin 6 of u7090. Guessing that connection is messed up even after I've cleaned it with alcohol.

Do you have to use hot air to do the replacement or can you use a soldering iron for this?

[piernov]

Re: 820-3435 No power / light

If the probe point, the track or the pad is corroded and broken, replacing the chip won't solve the problem. The problem would be rather solved by running jumper wires where necessary.
You need a hot air station to replace the chip, as well as a microscope to be able to work on those tiny components and traces and assess the damage, and fine multimeter probes. It sounds like you are lacking the proper equipment to perform Macbook logic board repair.

@MobileXT : please read the thread fully and try to understand where the problem lies with the information already given by the original poster before giving misleading advice.

[lebronballer]

Re: 820-3435 No power / light

If the probe point, the track or the pad is corroded and broken, replacing the chip won't solve the problem. The problem would be rather solved by running jumper wires where necessary.
You need a hot air station to replace the chip, as well as a microscope to be able to work on those tiny components and traces and assess the damage, and fine multimeter probes. It sounds like you are lacking the proper equipment to perform Macbook logic board repair.

Thanks piernov!

Yep, i don't have that equipment yet. Though I enjoy DIY and fixing things and would like to have them for any future repairs so i'll probably get them and try it out.