Macbook A1708 - 820-00840 20v 50ma

[obelix24]

Re: Macbook A1708 - 820-00840 20v 50ma

Ok cpu is probably dead i've removed U7650 cleaned pads and put it back if it will help bude then i noticed that the cpu was only getting hot. Now the board takes only 20v and 50mA again but there is no short on ppbus_g3h (i'm getting stable 13,08v) is there something how can i confirm that the cpu is dead ?

[mon2]

Re: Macbook A1708 - 820-00840 20v 50ma

Check the resistance of the CPU power rail to ground.

..

[obelix24]

Re: Macbook A1708 - 820-00840 20v 50ma

Resistance on test point (PPVCCCPU_S0G) to ground is 7ohms

[mon2]

Re: Macbook A1708 - 820-00840 20v 50ma

Measure the voltage to ground of PP1V_S5G.

[obelix24]

Re: Macbook A1708 - 820-00840 20v 50ma

there is 0V (I've connected power and USB is taking 20V 0,02a)

[mon2]

Re: Macbook A1708 - 820-00840 20v 50ma

From repair wiki for A1708:

Constant low power draw (10–20 mA): Short to ground on power rail (can be PPBUS_G3H, PP3V3_S5, PP3V3_S4,...)
Example: https://www.youtube.com/watch?v=jYa7KaPkZvg (19–20 mA draw, 0.7 Ω short to ground on PPBUS_G3H caused by bad capacitor, 1 Ω resistor of current sensing circuit from U7000 (ISL9239) also blown)

Missing PP3V3_S5G missing due to missing PM_EN_P3V3S5G, caused by bad (solder of) U7800 (PMIC), or corroded capacitors near it
Example: https://www.youtube.com/watch?v=ssTL3pKda54 (Short to ground on PP3V3_S4, PPBUS_G3H 13.7 V, bad capacitor, also damage to USB-C port, replaced CD3215 + other problems)

Power cycling 10–30 mA at 20 V: Check for short to ground on PP5V_S4

[obelix24]

Re: Macbook A1708 - 820-00840 20v 50ma

I'm missing PM_EN_P3V3S5G is there any place where i can securely inject voltage to find short ?

[mon2]

Re: Macbook A1708 - 820-00840 20v 50ma

First, remove all power. Measure the resistance to ground of PM_EN_P3V3S5G.

What is the resistance measurement?

As a confirmation, then switch to DIODE mode on your meter. Red meter probe, yes RED to ground. Black meter probe to PM_EN_P3V3S5G.

What is the diode measurement?

[obelix24]

Re: Macbook A1708 - 820-00840 20v 50ma

PM_EN_P3V3S5G Resistance to ground 9M ohms
Diode mode - 0,478V

[mon2]

Re: Macbook A1708 - 820-00840 20v 50ma

So the ENABLE to this power rail (PP3V3_S5G) is not shorted so no point to inject any voltage onto this enable signal line.

Review using the same method, the PP3V3_S5G power rail. If this power rail is shorted, then the enable line will follow and disable this power rail due to an excessive current draw.

What is the resistance on the PP3V3_S5G to ground ?

[obelix24]

Re: Macbook A1708 - 820-00840 20v 50ma

resistance to ground on PP3V3_S5G is 2,3M ohms
diode mode 0,340V

[mon2]

Re: Macbook A1708 - 820-00840 20v 50ma

No short here either. Is the current draw static or pulsing / cycling up / down ?

What is the voltage to ground of PPBUS_G3H ?

[obelix24]

Re: Macbook A1708 - 820-00840 20v 50ma

current draw is

Starts at 5V then it jumps to 20V (on both ports, all sides) it's approx 0,05A (it is slowly showing 0,052, 0,055, 0,057, 0,048) but it stays between 0,05 / 0,06A

Voltage on PPBUS_G3H (on F7000) is stable 13,09V

[obelix24]

Re: Macbook A1708 - 820-00840 20v 50ma

@Mon2 do you have any idea how to continue find problem ?

[mon2]

Re: Macbook A1708 - 820-00840 20v 50ma

Measure the voltage to ground of:

SMB_SMC_CHGR_SDA
SMB_SMC_CHGR_SCL

Post each measurement.

[obelix24]

Re: Macbook A1708 - 820-00840 20v 50ma

I'm not able to find this in board view for this board.
SMB_SMC_CHGR_SDA or SMB_SMC_CHGR_SCL

I'm only able to find
SMB_PMIC_SCL
SMB_PMIC_SDA

[mon2]

Re: Macbook A1708 - 820-00840 20v 50ma

See attached.

[obelix24]

Re: Macbook A1708 - 820-00840 20v 50ma

I've tested R5381 and R5380
pads : SMBUS_SMC_5_G3H_SCL and SMBUS_SMC_5_G3H_SDA

There is no test point or any component for SMB_SMC_CHGR_SDA or SMB_SMC_CHGR_SCL


both when charger connected show voltage 3.420V but it's not stable it drops to 3.3V and then back to 3.42V

see attached board view file

MOD Edit, boardview moved - https://www.badcaps.net/forum/showthread.php?t=69489
Reminder: rules and organization of this section - https://www.badcaps.net/forum/showthread.php?t=117483
.

[mon2]

Re: Macbook A1708 - 820-00840 20v 50ma

The 3v42 rail needs to be stable. Remove all power. Meter in resistance mode.

Measure the resistance to ground of the 3v42 power rail. Test anywhere you can.

What is the resistance?

[obelix24]

Re: Macbook A1708 - 820-00840 20v 50ma

resistance to ground on R5381 and R5380
pads : SMBUS_SMC_5_G3H_SCL and SMBUS_SMC_5_G3H_SDA

Is in Mega ohms (2Mohms and falling down)