Macbook pro A1278 820-2936 No light/turn on

[Adogabriel100]

Hey! how are you guys? i wonder if you could help me with this macbook 820-2936 that does not turn on. (Doesn't have green/orange light).

History:
this macbook came for a short on C6990 that blows D6990 and R6990 on his way. i re-placed the componets and it work again.

A month later comes back again and has the actual problem (no green/orange light and dont turn on)

The macbook can turn on with only the battery connected but in fact, dosent charge.

Voltajes:

PP3V42_G3H = 3.3v
PPBUS_G3H = 12.2V
PM_PWRBTN_L = 3.4V
PCH_SRTCRST_L = 3.4V
RTC_RESET_L = 3.4
PCH_INTRUDER_L = 3.1
PCH_INTVRMEN = 3.2
PCH_DSWVRMEN = 3.2
PP3V3_S5 = 0V
PP5V_S5 = 0V
PM_DSW_PWRGD = 0V
SMC_ADAPTER_EN = 0V

isl 625 (U7000):

(CHGR_AGATE) pin 1 = 0v
(CHGR_DCIN) pin 2 = 19.4v
(CHGR_ACIN) pin 3 = 4.7v
(CHGR_VFRQ) pin 4 = 3.4v
(CHGR_ICOMP) pin 5 = 1.2
(CHGR_CELL) pin 6 = 3.4
(SMBUS_SMC_BSA_SDA) pin 10 = 3.3v
(SMBUS_SMC_BSA_SCL) pin 11 = 3.3v
(PP3V42_G3H) pin 12 = 3.3v
(CHGR_RST_L) pin 13 = 3.3v
(SMC_BC_ACOK) pin 14 = 0.6v
(CHGR_CSO_N) pin 17 = 12.2v
(CHGR_CSO_P) pin 18 = 12.2v
(PP5V1_CHGR_VDD) pin 19 = 5v
(PP5V1_CHGR_VDDP) pin 20 = 5v
(CHGR_PHASE) pin 23 = 12.2v
(CHGR_UGATE) pin 24 = 12.7v
(CHGR_BOOT) pin 25 = 16.5v
(CHGR_SGATE) pin 26 = 19.1v (i think that this one has to be 0v in order to enable)
(CHGR_CSI_N) pin 27 = 19.4v
(CHGR_CSI_P) pin 28 = 19.4v


¿Do i need first PP3V3_S5 - PP5V_S5 to have a U7000 funcional?
dont know what im missing on this
i appreciate your help.
really thanks in advance.

[mon2]

Re: Macbook pro A1278 820-2936 No light/turn on

PP3V42_G3H = 3.3v

>> Start with this one, it should be 3v42.

What is the input voltage to this regulator?

Then, remove all power. Check the resistance of the feedback resistors used by this regulator. Do not power on while checking resistance and do not power on if these parts are removed.

[Adogabriel100]

Re: Macbook pro A1278 820-2936 No light/turn on

i'm sorry. i was measuring with my cheap multimeter

PP3V42_G3H = 3.44v
PPBUS_G3H = some times get 12.22 and 12.55

input voltaje on U6990 (3.425V "G3Hot" Supply)

from D6990 PPVIN_G3H_P3V42G3H to pin 7 of U6990
PIN 7 (VIN) = 19.77v

R6990 = 46.5 Ohms
R69951 = 0.85 Mohm

[mon2]

Re: Macbook pro A1278 820-2936 No light/turn on

PPBUS_G3H = some times get 12.22 and 12.55

SMC is waffling.

Remove the fuse on this line @ F7040.

Then power up again and check the voltage to ground at F7040, pin #1 (producer side).

What is the voltage measurement?

Next, power down, meter in resistance mode.

Measure the resistance to ground of F7040 PCB pad, pin #2 (consumer side).

What is the resistance mode reading ?

[Adogabriel100]

Re: Macbook pro A1278 820-2936 No light/turn on

Thanks for the help, mon2.


F7040, pin #1 (producer side). = 12.24v
F7040 PCB pad, pin #2 (consumer side). = 360kohms

[mon2]

Re: Macbook pro A1278 820-2936 No light/turn on

F7040, pin #1 (producer side). = 12.24v

Is this voltage stable or fluctuates upto 12v55 ? The resistance to ground reading is ok and there is no short on the PPBUS_G3H rail.

The voltage of PPBUS_G3H is configured using the SMBUS (SCL & SDA) lines by the SMC. The same SMBUS interface is shared by the battery back's BMS (battery management system). If either the SCL or SDA line is shunted due to a transient event, then all communication will halt.

Carefully measure the voltage to ground of the following points of interest:

SMBUS_SMC_BSA_SCL
SMBUS_SMC_BSA_SDA

Post the measurements.

[Adogabriel100]

Re: Macbook pro A1278 820-2936 No light/turn on

Is this voltage stable or fluctuates upto 12v55?

The voltaje just stay stable, 12.24v

SMBUS_SMC_BSA_SDA = pin 10 = 3.44v stable on pin 10 of u7000
SMBUS_SMC_BSA_SCL = 3.44v stable on pin 11 of u7000

[mon2]

Re: Macbook pro A1278 820-2936 No light/turn on

What is the voltage to ground of SMC_RESET ?

[Adogabriel100]

Re: Macbook pro A1278 820-2936 No light/turn on

SMC_RESET = 3.25v

[mon2]

Re: Macbook pro A1278 820-2936 No light/turn on

This is a good value.

Remove all power. Meter in diode mode. Touch your meter probes and confirm the tone beep.

Then one meter probe on the

SMBUS_SMC_BSA_SCL

And other meter probe to the closest point of the smc chip for the same trace. Do inspect for any corrosion.

Repeat for:

SMBUS_SMC_BSA_SDA

Want to confirm the SMbus traces reach their destination. The SMC chip is the SMbus master and the ISL chip is the smbus slave. If there is a broken trace, the voltage cannot be boosted for ppbus_g3h.

[Adogabriel100]

Re: Macbook pro A1278 820-2936 No light/turn on

there is not close test point or IC close to the SMC to check continuity. either way. i check the points and every point does its beep.

i check for corrosion (under microscope) and looks normal.

[mon2]

Re: Macbook pro A1278 820-2936 No light/turn on

What is the voltage to ground of ALL_SYS_PWRGD ?

[Adogabriel100]

Re: Macbook pro A1278 820-2936 No light/turn on

ALL_SYS_PWRGD = 0v

[mon2]

Re: Macbook pro A1278 820-2936 No light/turn on

What is the voltage to ground of SMC_BC_ACOK ?

[Adogabriel100]

Re: Macbook pro A1278 820-2936 No light/turn on

SMC_BC_ACOK = 0.69

some times the macbook turn on (im using BY-3200) and when i disconect the cable just dont turn on again.

i already change the U7000 and the SMC (before ask for help) and got the same behavior.

the u7000 from a know working board (yes, just for test) and the SMC from a donnor board.

[mon2]

Re: Macbook pro A1278 820-2936 No light/turn on

That is too low.

What is the voltage to ground of CHGR_ACIN ? Measure @ between R7010 & R7011. Post the measurement.

Remove all power. Meter in resistance mode.

Measure the resistance to ground of SMC_BC_ACOK. If the resistance is too low, this can cause this signal line to be with a low voltage.

Next, locate R5087. Check the resistance of this part across the 2 sides of the resistor. Is it ~470k ohms ? This resistor is required to pull-up the signal line to park to 3v42.

Next, meter in voltage mode. Confirm the voltage to ground on each side of the same resistor @ R5087. One side must be ~3v42.

[Adogabriel100]

Re: Macbook pro A1278 820-2936 No light/turn on

SMC_BC_ACOK = 400 Kohms

R7010 pin 1(PPDCIN_G3H) = 19.98 / PIN 2 (CHGR_ACIN) = 4.73v

R5087 = 415k ohms (measurement before taking it out of board)

R5087 pin 1(SMC_BC_ACOK)= 3.07v / pin 2(PP3V42_G3H)= 3.44v. (measurement after put another resistance)

OKAY. now... this happens; I take out R5087 from the board to measure the resistance. next thing. it blow from my tweezers. i put another one and the macbook it's turning on without any problem again (at least for now).

im not sure if that was the problem. maybe was the heat that i apply under SMC? really dont know. hope that this macbook dont come back

now im going to test it and see what happen.
thanks again for your time and help mon2. i really appreciate

[mon2]

Re: Macbook pro A1278 820-2936 No light/turn on

Awesome! See, that is a good omen for the resistor to fly away. This line was low and this resistor is needed to pull it high. Perhaps a bad solder joint. Run YouTube videos to stress test it. Hope it is stable for you. Reflowing the SMC is one of the suggestions for such cases.