Macbook Pro A1706 820-00923 no power after replacing top cover and keyboard

[johnbeton]

Hello,

I have a A1706 with 820-00923-A board. The laptop came in with non-working keyboard. I bought a new top-cover with keyboard and transfered everything to the new topcover.
Since then the macbook will not charge or power-up. Before replacing top cover, I started the macbook to test, and it worked fine apart from keyboard. Then shut it down and did replacement.
This is what I measure so far:


Resistance from F7000 to ground is 123 Ohm on pin 1 and 2

PPBUS_G3H = 0,79v
PPBUS_HS_CPU = 0,79v
PPBUS_HS_OTH5V = 0,79v
PPBUS_HS_OTH3V3 = 0,79v
PPBUS_S4_HS_TPAD = 0,79v
PPDCIN_G3H = 20,02v
PP3V3_G3H = 3,42v
PP3V3_G3H_SMC_ISNS = 3,42v
PP3V0_G3H = 0,37v
PPVCC_S0_CPU = 0v
PP5V_S5 = 1,07v
PP5V_S4 = 0v
PP5V_S4SW = 0v
PP5V_S4SW_ISNS = 0v
PP5V_S0 = 0v
PP5V_S0_KBD = 0v
PP3V3_S5 = 0v
PP3V3_SUS = 0v
PP3V3_S4 = 0v
PP3V3_S0 = 0v

[mon2]

Flux and remove F7000. Do not lose the fuse.

Then check the resistance to ground again using the PCB pads for F7000. Which side is with the low resistance? Producer side (ISL) or the consumer / downstream side ?

[reformatt]

I'd try first disconnecting everything external to the board, like keyboard and trackpad, then recheck your PPBUS_G3H resistance to ground. A bad trackpad can cause this, especially if it's liquid damaged.

I've also managed to knock some components off the board one time when I was being impatient refitting it to the chassis and dragging out some of the connectors that were caught underneath. Tip: Use sticky tape to hold these cables back when you are fitting the board!

[johnbeton]

I removed F7000 and the low resistance is on side of pin 2 PPBUS_G3H
Can I inject voltage on this pin to search for short ?
PS everything is disconnected and the board is disassembled.

[johnbeton]

I injected 1v 3A on pin 2 of F7000 but the system only draws 0.02 amps.
What would a normal resistance to ground be on F7000 pin 2 with fuse removed ?

[mon2]

With no power. Meter in red mode. Measure the resistance to ground of each pin on the battery connector. Checking if the smbus lines are defective.

[johnbeton]

- is 0,01Ohms
+ is NC

[mon2]

Need the vitals on the other pins of this battery connector. We are investigating specifically the pin # 2 and # 3 details which are the communicaton lines to the logic board and also linked to the PPBUS_G3H controller.

[johnbeton]

pin1 = 3,1 Ohm
pin2 = 10,2 KOhm
pin3 and 4 = variable from 35 KOhm - 125 KOmh (keeps going up and down)
pin 5 - 8 = 1,2 Ohm

[mon2]

What is the voltage to ground on F7000 pcb pad (ISL / producer side) with the fuse removed? Use only the power adapter.

[johnbeton]

I'm sorry, which side is ISL / Producer side ?
Pin1 = 13.08v
Pin2 = 0v

[mon2]

which side is ISL / Producer side ?
Pin1 = 13.08v

Pin # 1 on the removed fuse. Now you have a proper PPBUS_G3H voltage to ground. This confirms that the producer side = ISL9239 is working ok. The ISL9239 is the buck / boost regulator that accepts the 20V from the external power adapter and converts this to a lower voltage needed to power the logic board.

Respectively, the fault remains on the downstream or consumer side of the F7000 fuse, pin # 2. With a low resistance to ground on pin # 2, the ISL9239 is able to sense this heavy load and powers down the PPBUS_G3H rail.

With no power to the board, what is the resistance to ground again on pin # 2 of this removed fuse (F7000)?

[johnbeton]

at this point 119 omh

[mon2]

Remove all power. Suggest to measure the resistance to ground of each inductor. Searching for any inductor that may be close to this value of ~119 ohms. Post all suspects. If and when found, then place one meter probe onto F7000, pin # 2 (the downstream side) -> other meter probe onto the inductor that shows a similar resistance.

[johnbeton]

L8050 has the exact same resistance to ground. (other inductors have different values).
Resistance between F7000 pin 2 and L8050 is 1,8 Ohm.
Could U8050 be the suspect ?

[mon2]

Still working on my beauty sleep so do not have the schematics up at this time. This can be trouble as this usually implies that the high side mosfet that is on this found inductor is leaky. That is, if leaky, then the high voltage of ppbus_g3h has travelled onto the low voltage rail created by L8050.

Locate all high side mosfets on L8050. Check their resistance across:

source and drain
source and gate
gate and drain

Suggest to flux and remove the mosfet to test in the same way when the mosfet is on your table. The measurements should be high K ohms or more if not defective. Replace if lower resistance. Test again by as noted, often means the low voltage parts on this rail have been spiked by the high voltage leak.

[johnbeton]

ok, I will do so while you have your sleep :-)

[johnbeton]

I removed U8050: measured on the mosfet on table:
I have a 2 Ohm resistance from pin 3 to pin 9 (switching probes is same resistance)
And 1.6 Ohm resistance from pin 6 + 7 + 8 to pin 9

With U8050 removed, there is no continuity from F7000 pin 2 to L8050.
With power to the board I now have 13.08V on both sides of F7000.

So I think U8050 is bad.

[mon2]

Yes. Replace this part and test again. The transient that nuked U8050 may have caused additional damage. TBD.

[johnbeton]

I replaced the U8050 and PPBUS_G3H stays 13.08v, I have 13.08v coming in on pins 1 + 2 on U8050, but no output.
My probes of my multimeter are not small enough to measure pin 3 and 4 on U8050 without touching other parts.
Pin 5 to 8 are 0v.
I'm not a pro in reading schematics, but if I'm right, U7800 is switching the gates on U8050.