820-02020 stuck @5v

[phantom]

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



any hints? thanks

 

[2informaticos]

Check U8100 (SYM 3 OF 6) the 4 LDOs at page 33.

 

[phantom]

what do you mean with "4"...there are a lot of ldo on sym 3 of 6

PP3V8_AON_MPMU_ISNS_VIN 3,8v
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

 

[phantom]

PP1V2_S2 is not 0 but 1,2 floating

 

[2informaticos]

"there are a lot of ldo on sym 3 of 6"
Did you think what "NC" means in the name of other lines?

"PP3V8_AON_MPMU_ISNS_VIN 3,8v"
This is an input.
LDO means Low Drop Output...

MPMU_VREF_ADC still to check.

Now check U7700 LDOs (page 28).

 

[phantom]

I don’t know WHAT NC Means…

Is it normale that PP1V2_S2 is floating?

However i will check other ldo and mpmu thanks

 

[2informaticos]

NC menas Not Connected.

LDOs must be all stable.

 

[phantom]

MPMU_VREF_ADC is 0v
PP1V2_S2 and PP3v3_S2 are floating...
i've removed lc710 (and removing it i've broken it...) but still floating
0v on all u7700 ldo

about lc710..it is
1.5UH-20%-3.9A-0.048OHM

should i care about all specs? or for example only about uh? i cant find the exact type in my other motherboards

 

[2informaticos]

At least 1.5uH at 3.9A should match; 4-5A is good too.

"MPMU_VREF_ADC is 0v"
And diode mode?

 

[phantom]

0,570

 

[2informaticos]

You should try changing U8100.

 

[phantom]

very difficult to find isnt'it?

 

[2informaticos]

PMUs from 14" and 16" M1 boards are interchangeable.

 

[phantom]

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

all others ldo are 0v

 

[phantom]

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

 

[phantom]

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

I have 47 ohm resistence and 0,023 in diode mode on pp3v3_s2 Line..

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

 

[2informaticos]

Impossible to heat something with such low current.

You can think which components are most sensitive there.
Then try to remove one by one; is question of luck.

 

[phantom]

Do you think it’s a short Line?



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

 

[phantom]

i can clearly see that above wifichip become hot

removing rd810, short is gone...so now what?

 

[2informaticos]

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