Macbook Air A1466 No light on charger

[sircastor]

Hi everyone,

I have a MacBook Air 2015 (820-00165-02) that had some liquid damage. It was working for a while only on Adapter power, but that stopped working. Thunderbolt (external display) did not work. There was a bit of corrosion on the board, and I've cleaned that up. The adapter light does not turn on when I plug it in.

PP3v42_G3H: 3.42V
PPBUS_G3H: 0V
PPDCIN_G3H: 16.4V
PPDCIN_G3H_INRUSH: 0V

A lot of this is new to me, but following the schematic, I think that Q7180 is not producing the PPDCIN_G3H_INRUSH voltage, which in turn drives Q7130 to produce the PPBUS_G3 voltage. So my idea is to replace Q7180. My hesitancy (other than trying to find a replacement part) is that there might be some short somewhere else that damaged Q7180 in the first place.

There were a few spots of visible corrosion when I first got the board:

1. Where the wireless network card screws down, right next to D7005
2. To the Upper Right side of the SMC (U5000) near Y5110 and U3510
3. Around U3210
4. And around U3220 (Thunderbolt control)

I don't have a donor board to work off of. I'm sure I could get one off of ebay for relatively cheap, but then I risk just getting a board with components that also don't work. Any recommendations?

[mon2]

Remove all power. Meter in resistance mode. Measure the resistane to ground of PPBUS_G3H @ fuse F7140 (check both sides of this fuse). Post your measurements.

[sircastor]

Remove all power. Meter in resistance mode. Measure the resistane to ground of PPBUS_G3H @ fuse F7140 (check both sides of this fuse). Post your measurements.

I'm not particularly confident about these measurements. With a probe on ground (The shielding on the magsafe connector) and the other probe on either side of the fuse, I get the following readings:
PPBUS_G3H: ~3MOhm
PPVBAT_G3H_CHGR_REG: ~35KOhm.

However, in both cases the values roll up and down - I was really not able to get a reliable reading there. This makes me think I totally misunderstood what you were asking for - or the appropriate way to do it.
For what it's worth, the resistance on the fuse is negligible, but not infinite, making me think that it's still in-tact.

[mon2]

Suggest to use the negative side of a polarized tantalum (black body and rectangular in shape) capacitor for the ground.

Short the meter probes = should be a similar resistance across a fuse that is not blown.

[sircastor]

Suggest to use the negative side of a polarized tantalum (black body and rectangular in shape) capacitor for the ground.

Short the meter probes = should be a similar resistance across a fuse that is not blown.

Thank you, that was very helpful.

Either side of the fuse resulted in 0.3Ohm - it looks like it not blown.

[kevingill]

You'll need to get hold of a parts board if you're serious about repairing this. Otherwise you'll be paying more and spend your time waiting for parts.

[mcplslg123]

Thank you, that was very helpful.

Either side of the fuse resulted in 0.3Ohm - it looks like it not blown.

If resistance to GND on both pads of F7140 is 0.3 Ohms,then clearly PPBUS_G3H is shorted.

De solder the fuse and measure resistance to GND on both PCB pads again. One side will show high resistance and other side(system side) will show short To GND.

You need to inject 1V/5A on the shorted side and very likely tantalum cap near cpu will heat up.

[sircastor]

If resistance to GND on both pads of F7140 is 0.3 Ohms,then clearly PPBUS_G3H is shorted.

De solder the fuse and measure resistance to GND on both PCB pads again. One side will show high resistance and other side(system side) will show short To GND.

You need to inject 1V/5A on the shorted side and very likely tantalum cap near cpu will heat up.

This made me look at the Tantalum caps around the board to see if any of them were obviously blown or having trouble. They look okay, but I did notice some corrosion under the microscope that I hadn't seen before around C7140, C141, and C7143. I'll get out my hot air gun this weekend and take off the fuse as you suggest and see if that provides further clues.

I've got a parts board on the way to help me replace bad components.

And thank you!

[sircastor]

If resistance to GND on both pads of F7140 is 0.3 Ohms,then clearly PPBUS_G3H is shorted.

De solder the fuse and measure resistance to GND on both PCB pads again. One side will show high resistance and other side(system side) will show short To GND.

You need to inject 1V/5A on the shorted side and very likely tantalum cap near cpu will heat up.

Allright, I successfully got the fuse off (It was a struggle. All the youtubers make Hot air look like a cakewalk) and attempted to inject power (1V 5A from my Benchtop Power supply) and did not have any success. According to the PSU, it was drawing no current. I felt around the tantalum capacitors, searching for one that was heating up, but didn't find anything specific.

To be clear, I had my ground wire attached to a screw hole (easy to access ground) and the voltage wire on the PPBUS_G3H pin of the fuse footprint.



What can I look for next?

[kevingill]

With the fuse removed, do you get a voltage on pin 1 of F7140?
If not, I'd look at checking/replacing U7100

[sircastor]

With the fuse removed, do you get a voltage on pin 1 of F7140?
If not, I'd look at checking/replacing U7100

Are we talking about injecting voltage or through the normal power input?

[mcplslg123]

Share resistance to GND on both pads of F7140 while fuse is removed. No power attached while measuring.