MacBook Air A2179 - shorted trackpad, PPBUS_G3H stuck at 1,1v.

[Gueric]

Hello people !

I received an A2179 with a destroyed trackpad connector (all PPBUS_G3H_TPAD_FLT pads were destroyed). PPBUS_G3H was shorted to ground. I removed the trackpad connector, cleaned the area thoroughly, removed some bits of burnt copper, and short was gone. But PPBUS was stuck at 1,1v, even tho PPDCIN_G3H measured 5.2v So I replaced the 2 ISL's MOSFETs (Q7030, Q7040) in case they got killed by the short. Nothing changed.

I then replaced the ISL, still nothing. measured all its pads, good. resistors around the chip are also good. resistance on PPBUS was good, diode reading was a bit high (.510 instead of .410) and resistance was perfect.

Still nothing. absolutely no current draw, still 1v on PPBUS. so I removed the coil that connects PPBUS_G3H to these trackpad pads (PPBUS_G3H_TPAD_FLT), in case this mess was causing this, still nothing. I even replaced Q7680 and Q7660 just in case, absolutely nothing changed.

I've included a picture of the connector.

What should I do ? Maybe I've missed something? I'm out of ideas. Any help is appreciated.

[mon2]

Remove the fuse on PPBUS_G3H and test again. What is the voltage without the fuse on the isl side of this power rail? Is the voltage stable or cycling?

[Gueric]

Remove the fuse on PPBUS_G3H and test again. What is the voltage without the fuse on the isl side of this power rail? Is the voltage stable or cycling?

Sorry just to be sure, that fuse is F8400, one side PPBUS_G3H and the other side PPVIN_S0SW_LCDBKLT_F right? So just remove the fuse and measure its PPBUS_G3H pad?
Thanks for you reply

[mon2]

I am out of the office so do not have the schematics at this time. Locate the isl charger ic in the schematics. The fuse will be to the right side of this part and is on the main ppbus_g3h rail. We want to isolate the producer and consumer sides of this main power rail by removing the fuse.

[Gueric]

mon2 I just double checked, and there are no PPBUS fuses on the A2179 model. Only 2 fuses for the CD32s, one for the backlight circuit and one for the battery.

[mon2]

Test the vcore inductors L7210/L7220/L7230 in diode mode. Meter in diode mode. Remove all power. Red probe to ground. Black meter probe to the inductors. What are the measurements?

[Gueric]

mon2 all exactly 0.371

edit: if that helps, PPBUS_G3H reads 0.520 instead of 0.410 in diode mode

[mon2]

Cpu is not dead. Will post more once at the office.

[Gueric]

mon2 thank you very much. Will wait for your input

[mon2]

There are 2 versions of logic boards for the A2179. Which is yours?

820-01958 or 820-01055?


Check the diode mode measurements of all inductors onboard. See attached. No power to the board when testing in diode mode.

Red meter lead to ground.

[Gueric]

Here is your picture with the measurements I just made. mon2
Also this board is a 820-01958

[mon2]

Remove all power. Meter in resistance mode. Measure the resistance to ground of each pin on the battery connector @ J6950.

Post each measurement in ohms (not diode mode). Color of the meter probes does not matter in resistance mode.

We are checking if the SMBUS lines (used by the ISL9240) are shorted or not due to a transient on the battery connector (have seen this in the past).

[Gueric]

mon2

Pin 1: 2.8 Mohms
Pin 2: 2.8 Mohms
Pin 3: around 60 Kohms
Pin 4: around 360 Kohms
Pin 5: 3.3 Mohms
Pin 6 and 7 are ground.

I also checked in diode mode and they all match the values from OpenBoardData.

[mon2]

Measure the voltage to ground of pins 3 & 4 on the battery connector.

These are:

SMBUS_3V3_BATT_SCL
SMBUS_3V3_BATT_SDA

[Gueric]

Pin 3: 0V
Pin 4: 0V aswell

In case it's needed, Pin 1 and 2 read 1,1v (same as PPBUS) and Pin 5 reads 2,5v. mon2


Edit : left the board plugged for a minute, and Pin 5 reached 3,3v, and hovers around 3,1v to 3.3v.

[mon2]

Remove all power. Still in resistance mode. Measure the resistance to ground at L7690 = PP3V3_G3H.

[Gueric]

mon2 1 Mohms. slowly goes down

[mon2]

So not shorted but not on. In tracing this rail, the VIN for this rail @ pin 23 on U7650 and is fed from the missing PPBUS_G3H.

Measure the resistance across C7023.

[Gueric]

mon2 So across pin 1 and 2 of C7023 I get 2,50 ohm. To ground I get around 100 Kohms on both pins.

[mon2]

The input current sense resistance is ok and also not shorted.

What is the voltage to ground of PPDCIN_G3H? Is it stable?