820-2936 no green light

Yoel Ren

Member
Hi, this board came in with no magsafe light. I track down the problem to u7000, q7030, and q7035. replaced all, and magsafe green light come.
a few days later customer came back, no green light. i see ppbus is 12.2v. I have tried replacing smc 3 times.but still ppbus 12.2v and no green light. I test my smc to my sure working board and smc is good. so problem should be on board side.
i noticed smc_bc_acok is low at 0.7v at u7000.
its not shorted, diode mode is 0.473.
so to sum up
I have ppbus 12.2v
pp3v42 : 3.4v
smc_bc_acok 0.7v.

u7000 got proper dcin 16v, acin 4v, vdd 5.1v, and vddp 4v.
any pointer ? thanks..
for info, i have replaced u7000 a few times too, and quite sure its not the isl problem.
the whole board is kinda *not corroded,but oxidized. all probe point is dark.
 

2informaticos

Administrator
Staff member
The machine can work without Magsafe light; even with 12.2V at PPBUS_G3H.
Please post accurate information; no green light AND not turning on???

Check SMC_RESET_L first.
 

Yoel Ren

Member
yeah, no green light and not turning on.
smc_reset_l 3.3v good
these machine can turn on without green light ok, but these machine doesnt turn on automatically ( it should be )
 

2informaticos

Administrator
Staff member
Yeah U6901...

Sometime SMC_BC_ACOK drops when measure it, but no usual.
Resolder U6901 and check voltage at pins 4 & 5.

Do you have continuity between U6901, U7000 and R5087?
 

Yoel Ren

Member
continuity between u7000 pin 2 to u6901 is like 2 ohm.
I have tried measuring connectivity between sda scl smc to r5280 and r5281, its like 1 ohm. it should be as close as possible to 0 ohm. but everything is kinda not rly 'tightly' connected. maybe the board has some kind of flexion damagE ?
 

Yoel Ren

Member
i force it with 100k, but voltage is still pulled to 0.7v
I tried wire it directly, now I got green light and machine is turning on
any side effect ?
 

2informaticos

Administrator
Staff member
U5010 can be bad now.
Never force a pull-up resistor lower than 0.47-1 Kohm.
This value will prevent a sink current higher than 3-6 mA.
Sometime 100 ohm, even direct connection, can be used, but depends where.
 

Yoel Ren

Member
wow, ok. i actually ignore u5010 which have a oxidized feet because i thought smc_Bc_acok doesnt have anything to do with u5010, and I have pp3v42 anyway.
i replaced u5010, remove jumper and put proper r5087, and now green light and turning on.
thanks a lot man!
this should be the 'proper' way now.
care to elaborate how smc_bc_acok pulled down got anything to do with u5010 ?
 
Top