820-2936 no green light ppbus cycling 15.8v to 4v

[Yoel Ren]

hi, this board came in with flux around smc, I have 3.3/3.4v at pp3v42, smc_bc_acok and vcc, continuity good to adapter sense at pin 5 of j6900 too.. tried reflowing smc, sometimes it give green light but with looping fan spin every 3 second, but after a while, green light will be gone.
board start in smc bypass. ppbus is cycling from 15.8v to 4v, should I change smc first ?

 

[2informaticos]

SMC should be reballed, at least.

PPBUS_G3H reaching 15.8V points to shorted Q7030.

 

[Yoel Ren]

the ppbus value is when I have changed the smc, looking at other post, I maybe have some issue with sensor..
i tried to reball and replace back the original smc, I have ppbus 12.6v , no green light, but start in smc bypass.. 3v3_s5_avref is 3.3v

 

[2informaticos]

Check exact resistance between pins 17/18 and 27/28 of U7000.
Also check CHGR_A/BMON levels.

Be sure SMC_DCIN_VSENSE signal is good.

 

[Yoel Ren]

17/18 : 3 ohm , 27/28 : 20 ohm, I have tried replacing u7000 too.
chgr_amon 50mv
chgr_bmon 300mv
smc_dcin_vsense : 2.7v

 

[2informaticos]

In normal mode, any pulse on coils at least?
Be sure AVREF_SMC is OK.
Also check SMC_DCIN/BMON_ISENSE levels.

 

[Yoel Ren]

in normal mode, I tried monitoring pulse on L7260, L7330, L7510, no pulse.
pp3v3_s5_avref_smc is 3.3v
smc_dcin_isense : 0v
smc_bmon_isense : 0v

 

[2informaticos]

In normal mode, trigger SMC_ONOFF_L and check for drop pulse at PM_PWRBTN_L.
If yes, check for pulse at PM_SLP_S4_L signal.

 

[Yoel Ren]

i leave the board for a few days, when I came back, there's no green light anymore, I think the green light only present when I charge other macbook and right away plugged it back to the board.
anyway, I already used smc from another board that surely have green light, but after replacing it, I srill doesnt have green light, even though I have sys one wire voltage. Ialready checked resistor R4901/09 and R4902/98/99., allgood

 

[2informaticos]

Try known good DCIN board.
Check continuity from U6900 to central pin of Magsafe connector.
Post exact voltage at pins 4 & 5 of U6900.

Do you get 3V42_G3H?
What about PPBUS_G3H voltage now?