820-00850 dead 20v amp pulsing

[yair37]

very small water damage near UB300:
corrosion on: CB300 - PP3V3_G3H_RTC and CB308 - PP3V3_UPC_TA_LDO
replace both, all the voltage ok around UB300.
charger with battery: 20v and pulsing Amp 0A - 0.8A
charger without battery: 20V 0.04A stable.

 

[2informaticos]

Did you try DFU mode?

 

[yair37]

i was came this morning I assembled the board, suddenly i sew the empty battery icon on the screen i was connected the charger but the same(dead)
i put it in DFU mode tried Revive and Restore and get the error:
GAVE UP WAITING FOR DEVICE TO TRANSITION FROM DFU STATE TO DFU STATE (4005)
there is Trackpad activity when it try install.
tried also PRAM but nothing...

 

[2informaticos]

Do not confuse trackpad click with activity.

Did you try DFU with charger and battery, both connected?
With charger alone, do you get all AWAKE and SLPS2R voltages?

 

[yair37]

PP3V3_AWAKE pulsing 0v-3.3v

 

[yair37]

all AWAKE and SLPS2R voltages pulsing every 10-14sec

 

[2informaticos]

Shouldn't pulse if battery is connected; you've said to get battery icon image.

 

[yair37]

i measure with just board and charger.
i get the battery icon just one time..i dont get it anymore..

 

[2informaticos]

So test if you get stable voltage with battery and charger connected.

 

[yair37]

yes the same....pulsing also with charger and battery connected.

 

[2informaticos]

What about F7000 and L6900 voltage?
Test with charger alone and charger + battery.

 

[yair37]

L6900 - charger alone and charger + battery 3.4V stable!
F7000 - charger alone: 12.6v-12.3v pulsing
charger+battery: 12.8v -10v pulsing(stay at 10v for few sec and then up to 12.8v and then down to 10v and repeat.

 

[2informaticos]

There must be something else affected by liquid.
Inspect and reflow U7800 area.

 

[yair37]

i was reflow U7800 no change.. small water damage was just on CB300 - PP3V3_G3H_RTC and CB308 - PP3V3_UPC_TA_LDO. all the rest are very clear..
can it be UB300?

 

[2informaticos]

All USB ports have the same behavior?
An issue located on USB-C, shouldn't stop the board to work with battery.

 

[yair37]

yes all of them doing the same...what else can be?

 

[yair37]

all the port pulsing Amp from 0.070a to 0a just board and charger

 

[2informaticos]

I can only think to something elese affected by corrosion.
Not easy to find where...

 

[yair37]

succeed to enter DFU mode
one of the dots on the area i didnt notice that after the clean it was unconnected(PP1V8_MESA_FILT_CONN) its goes to the power button and because that it doesn't enter in DFU mode.
but dont pass the reviving.
also notice that AUD_CONN_RING2/SLEEVE full short.. should be like that?

 

[yair37]

suddenly it was turn on work for 2-3min then again shout off and back to 20v 0.04a...can i replace U7800?