820-00840 dead 19.7v and 0.01A

[kingskie]

Hi all,

i am working on macbook pro A1708 820-00840-A.
no history..customer just brought and say cannot turn on.

i plugged usb c amp meter and got 19.7v and 0.01A
check PPBUS_G3H 0.425V..check PPBUS_G3H but no short...but when measure for resistance i got 110 ohm on PPBUS_G3H..check for other rail but no short. can someone help?

[mon2]

Hi. Do not have a schematic in front of me at this time but often the PPBUS_g3h regulator is powered from a dual common-cathode diode. Search for it and post the voltage on each of the pins.

One pin is from the 20v adapter.

One pin will be from the battery.

Output pin will be to this regulator. This output pin must be close to the input rail value.

Post the measurements.

[kingskie]

Originally Posted by mon2

Hi. Do not have a schematic in front of me at this time but often the PPBUS_g3h regulator is powered from a dual common-cathode diode. Search for it and post the voltage on each of the pins.

One pin is from the 20v adapter.

One pin will be from the battery.

Output pin will be to this regulator. This output pin must be close to the input rail value.

Post the measurements.

hi mon2,

here i attached the schematic

[mon2]

Thanks. Post the voltages on each pin of D6905.

My bad, confirm that the 3v42 voltage is stable.

Then measure the voltage on both sides of F7000 fuse (ppbus_g3h). Still low voltage?

If yes, power down and remove F7000. Do NOT bypass it.

Just want to confirm that the power switching circuit is working to produce the ppbus_g3h rail ok.

What is the voltage if this rail without F7000? You will be measuring the voltage directly at pin #1 of F7000 pad.

[kingskie]

Originally Posted by mon2

thanks. Post the voltages on each pin of d6905.

My bad, confirm that the 3v42 voltage is stable.

Then measure the voltage on both sides of f7000 fuse (ppbus_g3h). Still low voltage?

If yes, power down and remove f7000. Do not bypass it.

Just want to confirm that the power switching circuit is working to produce the ppbus_g3h rail ok.

What is the voltage if this rail without f7000? You will be measuring the voltage directly at pin #1 of f7000 pad.

d6905:
Pin 1 0.43v
pin 2 20.1 v
pin 3 19.8v

pp3v3_g3h 3.4v

took off f7000
pin ppbusg3h 0.4v
pin ppvbat_g3h_chrg_reg 13v

[mon2]

Post the voltage readings on each pin of Q7030. Interested to know the voltage of SOURCE, DRAIN and GATE. Note there are 2 mosfets inside each.

Do the same for Q7040.

[mon2]

Adding to your list...

with F7000 removed, meter in resistance mode, no power to the logic board,

check & post the resistance to ground for the F7000 pad # 1

check & post the resistance to ground for the F7000 pad # 2

This is to allow us to check which side of the fuse is causing this heavy load.

[kingskie]

Originally Posted by mon2

Adding to your list...

with F7000 removed, meter in resistance mode, no power to the logic board,

check & post the resistance to ground for the F7000 pad # 1

check & post the resistance to ground for the F7000 pad # 2

This is to allow us to check which side of the fuse is causing this heavy load.

resistance to ground for the F7000 pad # 1 OL
resistance to ground for the F7000 pad # 2 115 ohm

[kingskie]

Originally Posted by mon2

Post the voltage readings on each pin of Q7030. Interested to know the voltage of SOURCE, DRAIN and GATE. Note there are 2 mosfets inside each.

Do the same for Q7040.

these measurements without remove the mosfet

Q7030
PIN 1-3 ------20V
PIN 4 ----------0V
PIN 5-6 -------GND
PIN 7-10 ------0V
PIN 11 --------0V
PIN 12 --------0V
PIN 13 ------20V
PIN 14 -------GND

Q7040
PIN 1-3 --------0.4V
PIN 4 -----------0V
PIN 5-6 --------GND
PIN 7-10 -------0V
PIN 11 ---------0V
PIN 12 ---------0V
PIN 13 ---------0.4V
PIN 14 ---------GND

[mon2]

Power down. Meter in resistance mode.

Please post the resistance readings for these same mosfets:

source to drain
source to gate
gate to drain

Review the resistance chart from this website for guidance:

http://electronicsbeliever.com/how-t...-is-defective/

[kingskie]

Originally Posted by mon2

Power down. Meter in resistance mode.

Please post the resistance readings for these same mosfets:

source to drain
source to gate
gate to drain

Review the resistance chart from this website for guidance:

http://electronicsbeliever.com/how-t...-is-defective/

i assume the mosfet is broken and replace it but still low on ppbus...could it be U7000 ?

[kingskie]

update for this problem, i replaced U7000 but still no luck..checked again and found out that PP3V3_TBT_X_F is shorted but i check the others PP3V3 line are not shorted..

any suggestion?

[kingskie]

update.. i found the short..it is C2977. but i lost some components when i open the shield. it is D3411, C3408 and D3403..is it ok if i dont replace the missing components regarding is is a supported components for usb C