840-00840-A 20V 0.01A S5 rails jumping

[linedot]

Hello, first time poster here - not a repair shop owner - just decided to try and fix a macbook I acquired recently.

Unfortunately, I don't know the MacBooks history - just purchased it as defective for cheap with the only info given "It suddenly didn't turn on anymore".

The case seems eerily similar to https://boards.rossmanngroup.com/threads/820-00840-s5-rails-not-steady.50493/ but the thread seems to have died without reaching a conclusion

Here are some not-quite-highres pictures of the board:

SMC bypass did not work. Here are some measurements I performed so far:

PPDCIN_G3H_CHGR = 20V
TBA_AUX_DET = 4.97V
TBA_VDDA = 5.20V
TBA_VDDP = 5.20V
PM_EN_P3V3_G3H = 5.20V
PP3V3_G3H = 3.41V
SMC_AUX_OK = 3.41V
SMC_RST* = 3.41V

D6905:
Pin 1: 13.04V
Pin 2: 19.92V
Pin 3: 19.66V

F7000: 13V both

P3V3S5_EN = jumps between 0V and 3V
PP5V_S5 = jumps between 3V and 5V
PP3V3_S5 = jumps between 0V and 3V
PP3V3_S5G = 0V
PP3V3_S5_S0R = jumps between 0V and 3V
PP1V8_S5G = jumps between 0mV and 23mV
PP1V_S5G = jumps between 0mV and 10mV

PPVCCPCH_S5G = 0V

PP3v3_S5_SMC_VDDA = 3.40 V
PP1v2_S5_SMC_VDDC = 1.22 V

PP5V_S4 = 0V
PP3V3_S4 = 0V

PP1V_S3 = 0V
PP1V2_S3 = 0V

PP5V_S0 = 0V
PP3V3_S0 = 0V

PP1V2_S0G = 0V

P5VS4_EN = 0V


U7890:

1 (SSD_PWR_REQ): 1.51V
2 (PMIC_EN_P3V3S5): jumps between 0V and 3V
3 (GND)
4 (PM_EN_PVXS5): jumps between 0V and 3V
5 (NC)
6 (PP3V3_G3H): 3.41V

PP5V_S0 = no short
PP1V8_S0 = no short
PP3V3_S0 = no short

PP1V_S3 = no short
PP1V2_S3 = no short
PP1V8_S3 = no short

PP5V_S4 = no short
PP3V3_S4 = no short
PP3v3_S4_WLS = no short

PP5V_S5 = no short
PP3V3_S5 = no short
PPVCCPCH_S5G = no short

PP3V3_S5G = no short

PP1V_S5G = short (Or just inductor (L8060,L1250,L1252,L1253,L1254) ?)
PP1V8_S5G = short (Or just inductor (L7930) ?)

PP3v3_S5_SMC_VDDA = no short

PM_SLP_S5_L = 0V
PM_SLP_S4_L = 0V
PM_SLP_S3_L = 0V

Considering I am seeing a small voltage on PP1V_S5G and PP1V8_S5G with the charger connected, I assume that those aren't shorted? Otherwise I would proceed by lifting the inductors and checking if the short remains. Can you help me with how I should proceed?

 

[2informaticos]

First of all, welcome to the forum!

"PP1V_S5G = short (Or just inductor (L8060,L1250,L1252,L1253,L1254) ?)
PP1V8_S5G = short (Or just inductor (L7930) ?)"
Post exact ohm value (NOT diode) to ground; measure 10-15s after power is removed.

 

[linedot]

Thanks for the welcome!

PP1V8_S5G ~ 0.2 Ohm (1.2-1.3 measured, 1.0-1.1 Ohm with just the probes (is my multimeter trash?))
PP1V_S5G ~ 0.4 Ohm

 

[2informaticos]

Almost pure short, not good.
Lift L7930 and L8060; check where the short remain.

 

[linedot]

L7930 and L8060 lifted.

Both shorts still there. Same measurements.

Anything to try before injecting voltage into the rail?

 

[2informaticos]

Which side of coils remain these shorts???

 

[linedot]

L8060:
Pin 1 (BANJO_SWVR1): no short, diode mode: out of range, resistance: OOR (>20MΩ)
Pin 2 (PP1V_S5G_REG): short, diode mode: 0.004, resistance: 0.4 Ω

L7930:
Pin 1 (BANJO_SWVR2): no short, diode mode: 1.930, resistance: 890kΩ
Pin 2 (PP1V8_S5G): short, diode mode: 0.003, resistance: 0.2Ω

PP1V_S5G measured from pin 1 of C8071: short, diode mode: 0.004, resistance: 0.4Ω

 

[2informaticos]

CPU is the common point for both power supplies.
99% dead CPU...

 

[linedot]

Well... French University of Christian Kings...

Thank you for the help!

Maybe I can find a repairable board for cheap somewhere