Apple MBP A1278 820-2530 - Brak reakcji

Witam

A1278
820-2530-A

Brak reakcji. Klawiatura/włącznik, gniazdo zasilania podmienione na sprawne. Restart SMC nie pomagał, nie włącza się też w trybie trzymanie włącznika 3s podpięcie zasilania, 3s i próba włączenia.
Zauważyłem nadpalony R6905 (opór był w porządku 47Ohm ale był delikatnie nadpalony więc go wymieniłem), nie dało to efektu jednak przy pomiarach zauważyłem dziwną rzecz że gdy dotknę sondą miernika n2 C6995 czy n2 R6995 lub n1 R6996 płyta zaczyna pobierać 140mA dotknę drugi raz pobiera 300mA.
Rozgrzewa to R6905 do takiego stopnia że "pływa".
Proszę o pomoc w naprawie.

Hello!

Do you have a green light on MagSafe?
Measure the voltage to ground on fuse F7000.
Measure the voltage to ground on coil L6995.
Measure the voltage to ground on pin 1 of chip U5000.

matic ha scritto:Do you have a green light on MagSafe?

Yes

matic ha scritto:Measure the voltage to ground on fuse F7000.

12.66V

matic ha scritto:Measure the voltage to ground on coil L6995.

3.4V

matic ha scritto:Measure the voltage to ground on pin 1 of chip U5000.

3.4V

Motherboard with only MagSafe and RAM consumption 38mA

U6901
n1 3.2V
n4 3.4V
n5 3.4V

Measure the voltage to ground on coil L7770.

Measure the voltage on capacitor C5710 in the following cases:
a) Power button released.
b) Power button pressed.

matic ha scritto:Measure the voltage to ground on coil L7770

0V

matic ha scritto:Measure the voltage on capacitor C5710 in the following cases:
a) Power button released.

3.4V

matic ha scritto:Measure the voltage on capacitor C5710 in the following cases:
b) Power button pressed.

0V

Measure the voltage on signal line "PM_PWRBTN_L" in the following cases:
a) Power button released.
b) Power button pressed.

Measure the voltage to ground on signal lines "PM_SLP_S3_L" and "PM_SLP_S4_L" in the following cases:
c) Before pressing to the power button.
d) After pressing to the power button.

matic ha scritto:Measure the voltage on signal line "PM_PWRBTN_L" in the following cases:
a) Power button released.

0V

matic ha scritto:b) Power button pressed.

0V

matic ha scritto:Measure the voltage to ground on signal lines "PM_SLP_S3_L" in the following cases:
c) Before pressing to the power button.

0V

matic ha scritto:d) After pressing to the power button.

0V

matic ha scritto:"PM_SLP_S4_L"

c) Before pressing to the power button.
0V

matic ha scritto:d) After pressing to the power button.

0V

Measure the voltage to ground on pin 1 of Q7800 with connected battery + power supply.

matic ha scritto:Measure the voltage to ground on pin 1 of Q7800 with connected battery + power supply.

Q7800
n1 0V
n2 0V
n3 3.3V

Measure the voltage to ground on pin 2 of resistors R2120, R2121.
Measure the voltage to ground on pin 5 of U2801.
Measure the voltages to ground on both pins of quartz Y2810.

matic ha scritto:Measure the voltage to ground on pin 2 of resistors R2120, R2121.

R2120
3.3V

R2121
3.3V

matic ha scritto:Measure the voltage to ground on pin 5 of U2801.

pins 1,4 1.6V
pins 3,2 0V

matic ha scritto:Measure the voltage to ground on pin 5 of U2801.

This IC is missing
pad 5 3.3V

How about the measurements on quartz Y2810?

Measure the resistances to ground on all coils.

sorry little mistake

matic ha scritto:Measure the voltages to ground on both pins of quartz Y2810.

pins 1,4 1.6V
pins 3,2 0V

matic ha scritto:Measure the resistances to ground on all coils.

L7000 2.7MOhm
L7320 16kOhm
L7260 23kOhm
L7220 4.7kOhm
L7400 37Ohm
L7401 37Ohm
L7620 162Ohm
L9701 396kOhm
L7770 460Ohm
L7560 5.4Ohm
L6995 188Ohm
L5850 23kOhm
L5801 0.8MOhm

Try to diagnostically heat the Nvidia PCH/GPU chip.

matic ha scritto:Try to diagnostically heat the Nvidia PCH/GPU chip.

no effect

It is probably bad SMC or Nvidia PCH/GPU chip.
More likely Nvidia PCH/GPU. You can try to reflow it, if it does not change anything, replace it.