MacBook A1278 820-3115-B does not work with adapter

hi
in MacBook A1278 820-3115-B lop top dose not start.i found C6405 shorted and after removing lop top turn on .
problem now, just working with battery.battery not charging .The MagSafe LED is off.with adapter P3v3S5_LL is ready.
and P5VS3_LL is zero(L7260).
in L6995 3.3v is ready.
please advise me for more test point.
tnx

Hello!

Perform the following measurements with the power supply connected:
- Measure the voltage to ground on pin 2 of fuse F6905.
- Measure the voltages to ground on pins 1, 4, 5 of chips U6900 and U6901.

hi
pin2 f6905=16.8v
pin1,4,5 u6900=3.4v
pin1,4,5 u6901=3.4v

Have you test the machine with a genuine Apple power supply?

Measure the voltage to ground on pin 2 of fuse F7040.

Please measure pin 5 (ADAPTER_SENSE) resistance to ground on J6900 connector and pin 4 of U6900 (DC-IN board disconnected).

hi
pin 5 (ADAPTER_SENSE) resistance to ground =1.8meg ohm
pin4 u6900=1.7 mega ohm
f7040=12v

Please now measure pin 5 (ADAPTER_SENSE) resistance to ground on J6900 connector while the DC-IN board is connected. Also, please measure the resistance between the central pin of DC-IN socket and pin 5 of J6900 connector.

both resistance(while the DC-IN board is connected) is more then 200 mega(open)
pin 5 with middle pin (dc-in not coneccted)=17k ohm
post update:
during measuring resistance ,magsafe led is turn on and every things is ok now :shock

Amir napisał(a):pin 5 with middle pin (dc-in not coneccted)=17k ohm

DC-IN board is faulty, should be 22Ω. Please post a clear photo of the solder side of your DC-IN board.

I hope you have the DC-IN board screwed tightly and correctly when testing the machine - if the DC-IN board is loose it won't work properly. Please re-measure the resistance between these 2 points (any direction):

hi
about 28 k ohm

Okay, please now measure the resistances between points marked 1 and, between points marked 2.

1=21k ohm
2=less than 10 ohm

Amir napisał(a):1=21k ohm

Measure this resistor directly on its pads - if you get the same value (21k), this resistor is faulty and should be replaced with 22Ω one (0402 footprint).


If this resistor does have the correct value of 22Ω, the PCB is damaged and you need to check traces under the microscope (you must get circuit continuity as shown below).

22 ohm is faulty.after Chang problem solved.
thank you very much Vogelek23 for support .