[HELP] 820-02020 stuck @5v

[phantomEVO]

hi to all, please help.

motherboard is perfect, no signs of corrosion or anything else.

both usb ports stays at 5v@0,04/0,05amps


PP3V3_UPC0/1_LDO & PP1V5_UPC0/1_LDO presents
PPBUS_AON 12.28v
PP3v8_AON 3.8v
PP3v3_S2 "bootloop" 2,8/3,0/3,1
PP1V8_S2 0V
PP5v_S2 0v
PP1v25_S2 0V

On u8100 i have
PP1V2_S2 0v floating 1,2
PP3V3_S2_UPC floating 3v/2,5/1,6/0
PP1V8_AON_MPMU 1,7
PP1V5_VLDOINT_MPMU 1,5
MPMU_VREF_ADC is 0v (no shorts)

on u7700 i have only one ldo output: PP1V8_AON_SPMU and it is 1,7v

all others ldo are 0v

around uf400 i have

PP3V3_S2_UPC3 3,3v floating
PP1V25_S2 0v
PP3V3_UPC0_LDO 3,3
PP1V8_S2 1,7 floating
USBC0_3V3LDO_EN 1,7 floating
UPC0_SS 0v
PP1V5_UPC0_LDO_CORE 1,5v
PPVBUS_USBC0 5v
PPHV_INT0_AONSW 5v

[mon2]

Remove all power. Meter in resistance mode. Measure the resistance to ground of PP3v3_S2.

[phantomEVO]

i've removed lc710 (to isolate the line but removing it i've broken it...)

47 ohm

in diode mode 0,023

[phantomEVO]

If i inject some voltage, the Line takes 0,050A but I can't find anything under termal camera

how is it possible that i have floating voltages even if i have disconnected lc710 where the short is?

[mon2]

Here is a replacement (1210 SMD size component) for LC710:

https://www.digikey.com/en/products/...AProsHiygAsOoA

To me, 47 ohms to ground and the diode mode readings are too low. Also wish to confirm that this measured low resistance to ground is on the consumer side of this power rail? This is from PCB pad #2 of the removed LC710 ferrite bead inductor?

Suggest to flux well and carefully remove the 3 caps on this power rail as per attached. Take your time to allow for the solder to melt. Then check the resistance to ground again for this isolated rail. Being caps with a polarity for CC715 and CC717 - be sure to note the position of the + side of each. CC718 is a not a polarized cap and is a ceramic device.

If not done already, disconnect the trackpad / camera / lcd assemblies and confirm this resistance to ground again. This power rail is used to power numerous current sense amplifiers.

[phantomEVO]

I'VE DONE ALL MEASUREMENTS WITHOUT LC710

i've done the meaurements on pad 2...

i’ve removed All 3 caps without luck

[mon2]

Be sure to check for thermals on both sides of the board. I think it will be safe to consider to increase the injection voltage (from 1v0) but keep under the 3v3 max. Increase the voltage slightly and monitor for heat. Repeat the process if necessary. This rail is not linked to the cpu. To confirm, nothing is attached to the logic board?

[phantomEVO]

it's strange, at 3,3v i can clearly see the upper layer of wifi chip become hot

removing rd810, short is gone

[mon2]

Aha!! Remove it and test again. Did see a current sense amplifier for the wifi linked to this power rail. Not at my desk but the wifi device could be also powered by this rail.

[mon2]

PS: could a nearby part be causing the heat? Investigate.

[phantomEVO]

mon2 could you explain me better? what do you want
to know?

[mon2]

removing rd810, short is gone

I am out of sync (unlike the boy band) - what is the resistance to ground now after the above part removal?

[phantomEVO]

I'm outside but i have no short anymore!

and if i go with power supply I have no amp sink!

maybe Could it be this the problem?

https://logi.wiki/index.php/M1_MacBo...I_Module_death

[mon2]

Sure looks that way Interesting to discover on our own. Very curious to hear of your progress after you replace the LC710 inductor. This power rail should now be stable. Good job.

[phantomEVO]

so i should fix the wifi problem and then replace lc710?

i dont understand: is this problem related to the fact that i have unstable ldo and macbook cant switch to 20v?

[mon2]

You do not need wifi to test the logic board. Will review the details of the removed RD810 component but if the short is gone, it is all good. From the shared link, the wifi module replaced will be a chore and risky to not lose the delicate bga pcb pads. Perhaps consider use of a usb wifi solution. First confirm this power rail was the fault before reviewing the wifi repair.

we may have multiple faults to review but this is definitely one of them.

[phantomEVO]

without rd810 i have on PP3v3_S2. 0,200 in diode mode and 0,500k resistence to ground...is it ok?

because on openboardataproject i should have 0,400 and 40m

soldering an 1.5UH-20%-12.5A-0.01OHM (just for test) in the place of lc710, i have 0,430 diode mode and higher resistence (i'm not able to read the value because it change continously...like from M to K)


but 3,3 is not stable

https://www.dropbox.com/scl/fi/4p5z7...skhjonmjm&dl=0


p.s i 've no problem to replace wifi module...but from what i understand, it is paired with cpu...so i can olny cut traces,,,,but i cutting traces i will lost power signal...FURTHERMORE IT SAYS: Without WIFI IC macOs triggers KP and not able to boot into OS.

am i wrong?

[mon2]

Yes, just read about the wifi being locked to the board and about the kernel panics. Is this wifi module with a metal shield that can be removed for inspection? To view the discrete parts under the RF shield? Do not have personal experience with this wifi module so best to wait for other comments.

Does this board power now? Check the power rail list again.

[phantomEVO]

Like I said before soldering an 1.5UH-20%-12.5A-0.01OHM (just for test) in the place of lc710, i have 0,430 diode mode and higher resistence (i'm not able to read the value because it change continously...like from M to K)


but 3,3 is not stable

https://www.dropbox.com/scl/fi/4p5z7...skhjonmjm&dl=0

and can’t switch to 20v

[mon2]

Based on the assorted public details of this wifi issue - this may be a no-fix board. A replacement known good wifi module is confirmed to allow for the board to boot without kernel panic but it does not function as a wifi port.

What is the resistance to ground of PP1V8_S2 ? This non-working power rail is also used to power the defective wifi module.