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[SOLVED] 820-3435 PM_SLP_S4_L 0.9v

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M

MUUK

Member
dry board. Green light on charger CPU cold, no light on USB fan spinning.


Found exploded cap C7600
replaced it and U7600 to be safe.
Checked for shorts to ground then tried powering.
Get green light but no fan spin

Missing PP5V_S4RS3
checked U7501 was missing P5VS4RS3_EN_R and SMC_PM_G2_EN


SMC_RESET_L 3.3 - OK
PM_SLP_S4_L 0.9v - BAD

R1481 measures 10k not 100k replaced it - STILL reads 10k.


Does this mean PM_SLP_S4_L pulled low by dead PCH ?

Grateful for any help.
 
Gurmon

Gurmon

Member
MUUK said:
Does this mean PM_SLP_S4_L pulled low by dead PCH ?
Click to expand...

No not necessarily.

You've got more measuring and inspection to do.

So, you have ppbus_g3h, PP3v42_G3H &, PP3v3_s5 & PP5v_s5 ?


There's plenty of paths to ground for PM_SLP_S4_L to escape other then through the PCH.

I would still look for corrosion somewhere, the amount of times I've found corrosion on a board that looked clean.......
 
larossmann

larossmann

Administrator
Staff member
0.9v is not a valid state. 3.3v makes sense. 0v makes sense. very quick, barely readable pulses from power cycling make sense. But 0.9v - that isn't valid at all.

Is PP3V3_S5 present?

R1481 doesn't exist on this board. Either way, resistors used in these circuits fail to a higher resistance, not a lower resistance, so this doesn't count. Don't bother replacing resistors if they measure a lower resistance than their stated resistance and do not appear damaged. If something else is connecting point A to point B in other sections of the board you are measuring everything around the resistor as ell and of course if these paths exist you will see a lower resistance.
 
M

MUUK

Member
My apologies. It was R1461 mentioned incorrectly as R1481 above. Thank you for telling me about the lower resistance.


started again and re-checked power rails today.




PPBUS_G3H 8.6v
PPBUS_S5_HS_COMPUTING_ISNS 8.6v
PPBUS_S5_HS_OTHER_ISNS 8.58v
PPVRTC_G3H 3.32v
PP5V_S5 4.99v
PP3V3_S5 3.32v


PP3V3_S4 0.03v
PP5V_S4RS3 0v


SMC_RESET_L 3.38v
PM_SLP_S4_L 0.19v (different to yesterday)


U7501

pin4 (EN1) 0.06v
pin23 (VIN) 8.6v
pin20 (S5_PWRGD 3.3v
pin21 (P3V3S5_EN_R) 3.46v
pin 12 (SMC_PM_G2_EN) 3.4v (this was missing yesterday)


So I have all S5 rails present, PPBUS_G3H is at 8.6 and the SMC seems to be working.


Checking back on P5VS4RS3_EN_R
R7551 0.04ohm
R8179 0.2ohm

PM_SLP_S4_L at R8179 0.19v
 
M

MUUK

Member
Hi Duke,

Resistance to ground (red probe on cap, black probe on gnd) starts 4.83kohm then rises quickly and keeps going.

Diode mode to ground (black probe on cap red probe on gnd) 0.455v drop.
 
M

MUUK

Member
Did some further checking. C7601 and PP1V05_SO is shorted to ground. Removed C7601 U7600 and short is still present. Would this stop the machine going to S4 ?
 
M

MUUK

Member
Lifted the coil L7630 - short is on system side (boo). Removed C7623, C7648 & C7649 short still present.
 
M

MUUK

Member
Resistance to ground 0.9ohm. Diode mode 0v drop to ground.
If i lift the coil L7630 i get 0.9ohm system side (pin2) and 470k other side - which matches the reading on my donor board.
 
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