820-3115 ppbus_g3h keeps shorting

Gmorb

Member
Ppbus_g3h keeps shorting. I get a green flickering light on charger then it will go away ppbus_g3h will short on r6905 short goes away when removed if i replace component same thing repeats. What could be wrong?

seems like the shorting has stopped but im only getting 1.5v on ppbus_g3h and ppdcin_g3h fluctuates from 15.80v to 16.80v
 
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JohnB8812

New member
Ummm so yeah both current sensing circuits are blown lol and likely the ISL as well. Replace current sense resistors and ISL but check that the traces are good from the ISL throughout the sense resistors or it won't fix anything.
 

Gmorb

Member
So replaces all the components on those circuits as well as isl and board turns on but wont charge battery.
 

JohnB8812

New member
Does it see that battery in the OS or do you get an X in the battery? If it sees the battery, check resistance between 17/18 and 27/28 again to make sure they measure properly I suspect something may still be wrong there
 

Gmorb

Member
i realized the board is powering on but its brain dead? i get no cpuvcore current sensing. Could be why its not charging but if not then Lgate on isl is only getting .600v everything else checks out.
 

aprendiz

Moderator
ok lets see, you say:

3v42 is present
17/18=32mohm
27/28=22mohm

You mean Megaohm?? if yes, both are absolutely wrong and if you already replaced resistors the problem could be a broken trace on sense circuits, if you mean Ohm the first is wrong the second is fine, so, what is it....
 

Gmorb

Member
u7000
17/18=3.6 ohm
27/28=20.9 ohm

i think that circuit is good. the next issue i found was cpuvcore is not getting any voltage after doing some digging i found that CPUIMVP_BOOT1 on u7400 is only outputting 4.85v LGate and UGate output nothing. ive already tried replacing u7400 but results are the same. so cpu is not powering on any help appreciated.
 

dukefawks

Administrator
You cannot just measure LGATE/UGATE, they are switching outputs and will not read anything useful on a multimeter. ALL_SYS present?
 

dukefawks

Administrator
U7400 is not being told to output by the CPU. Could be anything, crap under SMC, dead CPU, etc. All depends on where the liquid was.
 
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