820-2850 wont charge

[nate8organic]

Hi customer brought back a board i fixed the u7000 on. https://www.rossmanngroup.com/board...lved-820-2850a-shorted-out-on-the-u7000/page2

I retested the u7000

pin 1 - 4.1v
pin 2 - 4.47v
f7040 - 12.3v
u7000 res 27/28 - 21.3 ohms
17/18 3.1 ohms

Is this the isl again? and what would likely cause it to go out again?
thanks
nate

 

[2informaticos]

12.3V means SMC doesn't work correctly...
Do you get green light on magsafe?
Check battery bus lines to ground and voltages.

 

[aprendiz]

SMC_RESET_L is present??? If yes, this is a bad SMC.... Was this water damage in the first place??? Apply some flux and heat to see if it come back to life...

 

[dukefawks]

It is a data bus issue. Could be battery/ISL/SMC/battery indicator. Anything connected to SMBUS_SMC_BSA is suspect.

 

[nate8organic]

okay iv narrowed it down to the SMBUS_SMC_BSA_SDA. voltage there is varying from 115v up to 350v over and over.

im getting a solid 12v on the R5280. so is this the isl because im not 100% sure if the r5280 goes directly to the isl..

Also now wile i was testing near the isl the charger light has gone from green to nothing. but now im getting 114v on R5280 after the green light stopped working.

 

[dukefawks]

I have no idea what I'm reading.....350V seems pretty dangerous to me!

 

[nate8organic]

yeah same thing i was thinking. now that my green light is gone, i checked the probe for SMBUS_SMC_BSA_SDA and now im getting a solid 96mv. also the board wont power on anymore. i was testing voltage near the r5280 when the green light went off.

 

[dukefawks]

350V will kill you if you touch it! No idea what is going on there.

 

[2informaticos]

Stop using auto-range.
Use cheap multimeter in 20V scale, avoid any missunderstood this way...
Post PPBUS_G3H and 3V42 values now; voltages and resistance to ground too.

 

[nate8organic]

okay 2informaticos thanks for that!

3v42s @3.3v

ppbus_g3h @ .4v

r5280+ r5281 @ 0V

 

[2informaticos]

"and resistance to ground too"
In case if PPBUS_G3H is 0.4V only...

 

[nate8organic]

oh yeah sorry forgot to grab that.

res to ground

ppbus_g3h @ 0 ohms

3v42@ 1 ohm

 

[larossmann]

It seems like you have a short to chase on PPBUS_G3H. My guess is shorted Q7535/Q7530. Inject 1v on PPBUS_G3H, try and find what gets hot. I feel like full story is missing here, first you went from it turning on but SMBUS issue where SMC couldn't tell ISl what voltage to set, now it's dead...

 

[2informaticos]

3v42s @3.3v
3v42@ 1 ohm
This can't be real...
I hope you don't measure resistance to ground with power...

 

[larossmann]

I missed that. I'm glad we have our newly registered puppy to correct me. Your measurements make no sense and are fucked. I can't give you advice until measurements start to make sense again.

 

[2informaticos]

No power means battery removed too!!!
Is that the case?

 

[nate8organic]

i have no power connected to the board. no battery and no power supply just a board nothing connected. did you want me to test the voltage also with no power to the board? i am familiar with testing boards resistance/ voltage.

im not sure why i'm getting 1 ohm with proper voltage so i'm wondering if this may have something to do with things not working.

i also should note that when the green light stopped coming on when i'm guessing i shorted something together next the the u7000, it also fried the power i/o and when i was testing other boards i noticed this and swapped it out for a new one. i dont know if that helps shed any light on things, (i forgot to mention this in the intro)

 

[dukefawks]

It is impossible to have 3V42 present and have a 1 Ohm short. No idea what you are doing, please learn how to use a multimeter.

 

[nate8organic]

Okay im not sure what is happening. i am including videos of my test, please let me know what/if im doing something wrong here so i can improve/correct my mistake(s). As far as i know i know how to use a multimeter, iv only had 2 instances where the auto-range affected my results.