macbook 820-00239 20v no power missing pp3v3_s5

[manusg]

hello everyone
this is my first time posting
i want to thank everyone for everything because i found a lot of solutions in here
i have repaired a lot of macbook logic boards and i consider i have some experience but a lot to learn still

this time i couldnt find the solution anywhere so here i am
this a1706 logic board i have was taking 20v and 120mA stucked

i opened it up and did a visual inspection and it was all good except from U7650 which had some corrosion between the ic and C7651 i tested C7651 and shorted
so i removed C7651 and U7650 and replaced with new ones
now i have 20v and 20mA so i started testing that area
I have:
pp5v_s5 - 5V
pp5v_s4 - 0V
pp3v3_s5 - 0V
pp3v3_sus - 0V
p5vs5_en - 3.4V
p3v3s5_en - 3.4v
PPBUS_HS_OTH3V3 - 13v

i know i must have all my s5 in order to have s4 so since i dont have pp3v3_s5 i dont have pp5v_s4

what im not understanding is why if im having power Vin in U7650 also i have p3v3s5_en why im not having the output of pp3v3_s5 ?
any help would be really appreciated
i have osciloscope so i can test anything you suggest
thanks!

[mon2]

Re: macbook 820-00239 20v no power missing pp3v3_s5

What is the voltage at PPBUS_G3H ?

[manusg]

Re: macbook 820-00239 20v no power missing pp3v3_s5

What is the voltage at PPBUS_G3H ?

ppbus_g3h is ok - 13V

i also forgot to mention pp3v3_s5 is not shorted

[mon2]

Re: macbook 820-00239 20v no power missing pp3v3_s5

Are you confident of the replacement and soldering of U7650 ? They commonly fail -> consider to flux the device -> low air pressure but high heat and allow the part to swim onto the pads. 'Make it dance' to confirm the device is properly seated onto the pads.

Do so with patience so that no parts go flying or any SMD pads get damaged. Use a tweezer to slightly nudge the part when the solder is liquid. The part should bounce away with the small push but will bounce back, naturally. This creates a good bonding onto the PCB.

[manusg]

Re: macbook 820-00239 20v no power missing pp3v3_s5

Are you confident of the replacement and soldering of U7650 ? They commonly fail -> consider to flux the device -> low air pressure but high heat and allow the part to swim onto the pads. 'Make it dance' to confirm the device is properly seated onto the pads.

Do so with patience so that no parts go flying or any SMD pads get damaged. Use a tweezer to slightly nudge the part when the solder is liquid. The part should bounce away with the small push but will bounce back, naturally. This creates a good bonding onto the PCB.

yes yes i know how to solder properly
i been doing boards repairs iphone and mac for 5 years
and i tried two different u7650
that is not the problem

[mon2]

Re: macbook 820-00239 20v no power missing pp3v3_s5

Good.

Measure and post the voltage values of the following:

P3V3S5_CSN2
P3V3S5_CSP2

Remove all power. Meter in resistance mode. Confirm the resistance of the network for the P3V3S5_VFB2 are matching the schematic.

Specifically, confirm the resistance of:

R7697
R7698
R7699

Still with no power to the logic board, meter in resistance mode, check the resistance of the switching dual mosfet @ U7660.

Check the resistance of U7660 as follows:

pin #1 & pins # 6-7-8
pin #1 & pin # 3
pin #3 & pin # 6-7-8


pin #4 & pin # 9
pin #4 & pin # 5
pin #5 & pin # 9

Post the readings.

[manusg]

Re: macbook 820-00239 20v no power missing pp3v3_s5

Good.

Measure and post the voltage values of the following:

P3V3S5_CSN2
P3V3S5_CSP2

Remove all power. Meter in resistance mode. Confirm the resistance of the network for the P3V3S5_VFB2 are matching the schematic.

Specifically, confirm the resistance of:

R7697
R7698
R7699

Still with no power to the logic board, meter in resistance mode, check the resistance of the switching dual mosfet @ U7660.

Check the resistance of U7660 as follows:

pin #1 & pins # 6-7-8
pin #1 & pin # 3
pin #3 & pin # 6-7-8


pin #4 & pin # 9
pin #4 & pin # 5
pin #5 & pin # 9

Post the readings.

Ok thank you! Will do that tomorrow and come back with the info you requested

[manusg]

Re: macbook 820-00239 20v no power missing pp3v3_s5

Good.

Measure and post the voltage values of the following:

P3V3S5_CSN2
P3V3S5_CSP2

Remove all power. Meter in resistance mode. Confirm the resistance of the network for the P3V3S5_VFB2 are matching the schematic.

Specifically, confirm the resistance of:

R7697
R7698
R7699

Still with no power to the logic board, meter in resistance mode, check the resistance of the switching dual mosfet @ U7660.

Check the resistance of U7660 as follows:

pin #1 & pins # 6-7-8
pin #1 & pin # 3
pin #3 & pin # 6-7-8


pin #4 & pin # 9
pin #4 & pin # 5
pin #5 & pin # 9

Post the readings.

ok this is becoming a nightmare
i have a fully working 820-00239 board so i compared all the measurement you asked me and everything was ok

when i was taking all those measurement you asked i noticed something weird on U7660 so i changed it after that i powered up the board again and it was taking 20 mA more than before but still not booting of course

i unplugged and measure PP3v3_S5 again and now its shorted to ground
i removed u7660 and the short is still there
so out of the blue now PP3v3_S5 is shorted giving me 1 ohm to ground

so now i know if i have a short i inject voltage and look with the thermal camera for the hot spot the problem is nothing get warm

im injecting 1.5v in PP3v3_S5 and my power supply is consuming 2amps so i should get some heat somewhere in the board but im not

i even removed the heat sink thinking that maybe cpu was getting hot but no its cold as a stone

so now this is my problem PP3v3_s5 shorted injecting 1.5v getting 2amps but NOTHING gets warm

i looked for shorts many times ago and everytime something gets warm i never had a case like this before

[mon2]

Re: macbook 820-00239 20v no power missing pp3v3_s5

Remove (carefully) UB600 and check the resistance of this rail again. It is a DFN package so should be ok to return back if it is not the fault.

UB600 is a load switch for this rail.

This same rail is also used to power the SSD. Are you able to check the thermals of the SSD devices?

Another thought is to remove the LIFEBOAT connector @ J9600 which will then isolate the connection from pins 45 to 46. With this 'top hat' shunting jumper block removed, you can check the resistance to ground again to sub-divide the vicinity of the short.

[Pedro147]

Re: macbook 820-00239 20v no power missing pp3v3_s5

Hi @mon2, I just wanted to thank you for the info in this thread. It just helped me fix an 820-00923 board that I was having trouble with. I looked at U7650 because of what you said here and after measuring the PP3V3_S5 and PP5v_S5 outputs and the enables for those outputs, I thought that it might well have a faulty U7650 which it did. So thanks again for all the help that I have seen you give to people in here, I for one greatly appreciate it

[mon2]

Re: macbook 820-00239 20v no power missing pp3v3_s5

Excellent ! Thanks for positive feedback.