820-3437 PM_SL_S4_L 0v.

[MUUK]

History: Dog piss on logic board (yes, customer admitted to dog piss).

Was turning on but no backlight, had major damage to the backlight and intMD/lvds area. Stripped the intMD/lvds connector and replaced all the components (fuse, 1012 caps, coil etc) until i got 0.542 diode mode reading on backlight output. Checked for shorts to ground on all replaced components. Lp8550 feedback was fucked so ran a wire, that was all good.

Plugged in AC (known good Apple original 85w) got fan spin for 2 seconds then powered off. Now when AC power applied machine does not spin fans or go on from S4 > S4 state.

Checked backlight fuse (still good), re-checked backlight area for shorts, still good.
Removed the backlight fuse to see if anything further up was causing it, but no change.

Then back to testing power rails (results below) i've tried to follow this back through the schematic as far as i can but i'm getting a bit lost. Here are the readings i have taken so far.


S5 rails

PPBUS_S5_HS_COMPUTING_ISNS present
PPBUS_G3H present
PPBUS_S5_HS_OTHER_ISNS present
PPDCIN_G3H_ISOL 16.6v present
PPVRTC_G3H 3.3v present
PP3V3_S5 3.3v present

PP5V_S4RS3 missing
PP3V3_S4 missing

U8080 0v at pin 2/3 (enable pin)
5v present at pin 29 of U7501
Q7520 pin 1/3 8.5v all other pins 0
U7501 pin 4 P5VS4RS3_EN_R is 0v)
U7501 pin 21 P3V3S5_EN_R is 3.4v

so i believe the problem is on U7501 not turning P5VS4 on
R7551 is showing as 0.5ohm
C8175 appears to be missing from the board - is this so ?
R8177 is missing also....
R8179 is present on the board (PM_SLP_S4_L) and is 0v
R1461 (PM_SLP_S4_L nearest SMC) 0v

SMC_ONOFF_L is 3.4v at C4834 and at R5170.

I realise these PM_SL_S4_L issues are tricky but am hoping the Rossman / Duke gods can suggest anything that can help before i move on.

 

[larossmann]

Is PM_DSW_PWRGD present, was there corrosion at all around the U1950/ALL_SYS_PWRGD areas? Corrosion on backlight area puts you close to corrosion on SMC area. What does J6100 look like?

 

[MUUK]

Thank you Louis.

the dog piss was very localised in the LVDS area as far as i could see, but it made a right mess.

PM_DSW_PWRGD measures 3.4v at R8141, R8141 measures 93K ohm (vs 100k on schematic so ok).

No corrosion around U1950 that is obvious, here are the pin voltages / diode mode in case that helps

U1950

pin voltage diode mode rail

pin 1: 0v 0.411 ALL_SYS_PWRGD
pin 2: 0v 0.668 CPUVR_PGOOD_R
pin 3: 0v 0.646 SYS_PWORK_R
pin 4: 0v 0 GND
pin 5: 0v 0.634 PM_S0_PGOOD
pin 6: 0v 0.667 SMC_DELAYED_PWRGD
pin 7: 0v 0.635 PM_S0_PGOOD
pin 8: 3.42v 0.303 PP3V42_G3H


working backward from U1950

looked at CPUVR_PGOOD_R
R1951 (not present)
R1955 0.03v either side resistance 10k ohms.
then noticed it says NO STUFF on schematic so presume that the only input to U1950 is ALL_SYS_PWRGD as CPUVR_PGOOD_R is no stuff.

J6100 looked very clean but i have removed it anyway.

followed schematic back on ALL_SYS_PWRGD but this lead me to U8160, R8164-r8167 but these seem to be produced when in an S0 state, which we are not in.

R5100 SMC_RESET_L is 3.42v

thank you again.

 

[MUUK]

Further testing:

u7501 pin 12 is 3,42v
SMC_LSOC_RST_L =3.42v
SMC_RESET_L 3.42v at R5100 and at R7100
SMC_ADAPTER_EN R5185 3,42
SMC_PM_G2_EN is 3.42
SMC_CLK32K is 0v

PP3V3_SUS is 0.7v not 3.42 at R6101
U8020 area C8020 PP3V3S present 3.39v
following back to P3V3SUS_EN
R8190 is 3.3v
pin 1 of R8020 PP3V3_SUS_FET_R 3.4v (not present resitor)
looking at U6100
R6102 0v

am i following this in the right direction do you think ? is 0.7v at R6101 PP3V3_SUS due to PM_SLP_S4_L being low or could it be causing it.
Could i jumper R8020 pin 1 to R6101 for testing ?

 

[dukefawks]

So 3V3_SUS is present at R8020. It is not present at R6102 so there must be a corroded trace somewhere. Run a wire from R8020 to R6102.