820-2936 short fan spin on charger only, runs on battery

grmacs

Member
This board ran on battery but had no green light. Found corrosion around Q5310 and that edge of the board and had .7V at SMC BC ACOK. Replaced Q5310 and got green light and PPBUS G3H and short fan spin but stops... PPBUS G3H stays steady at 12.62V once connected to power and after fan starts and stops.
 

grmacs

Member
It DOES. Never used that to test before... what does that imply? AFter poking around the posts a bit... being it runs ok on battery does this mean then that SMC current sensing related to the charging circuit is awry?
 
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2informaticos

Administrator
Staff member
Most likely.
Check resistance between pins 17/18 and 27/28 of U7000.
Also check SMC_DCIN/PBUS_VSENSE and SMC_DCIN/BMON_ISENSE.
 

grmacs

Member
85w Charger only connected:
17/18 resistance 3.0 ohms
27/28 20.9 ohms
dCIN VSENSE 2.8V
PBUS VSENSE 2.1V
DCIN ISENSE 0V
BMON ISENSE 3.4V
 

2informaticos

Administrator
Staff member
Aaaah, you get short fan spin in normal mode.
Then must be a SMC sensor from other rail.
Check all other sensor circuits from pages 49/50.
I bet for some corroded trace, or resistor.
 

grmacs

Member
lost a pad on the smc trying to reball it. DOn't have another 2936 board! I'll have to put this one on the shelf until I get a SMC for it. I was thinking it had to be SMC related being the battery op runs fine and charger sensors seem to be reading correctly? Idk. I couldn't identify any sensor issues related to the pages you referenced but I'll try again once I get SMC back on it.
 
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