820-2915 PP1V5_S3RS0_CPUDDR problem

[geraymartha]

Hello guys i have a 820-2915 missing PM_SLP_S4_L no 5V_S3 , after some trouble shoot i find out that PP1V5_S3RS0_CPUDDR as soon as it gets into Q7950 send all to hell , if i remove R7954 , i get a PM_SLP_S4_L and working s0 rails , no fan spin , i did replace Q7950 no result , i did remove Q9607 and U9950 to see if problem was ahead , but no , i still dont check all resistors around q7950 , i did follow this problem to this location from long way , and i got burn. plz help.

 

[geraymartha]

i just check all resistors around Q7950 they are fine

 

[geraymartha]

with R7954 removed

ALL_SYS_PWRGD is 0.07v
PP1V05_S0 is present
PP1V5_S3RS0_CPUDDR is present
PP3V3_S0 is present
PP3V3_S5 is present

with R7954

fan spins then stops , then spins , then stop.
no 5v_s3

 

[geraymartha]

i did remove R7974 to disable the contact between U7400 and ALL_SYS_PWRGD problem is not on u7400 area since ALL_SYS_PWRGD remain 0v

 

[geraymartha]

i just try another U2800 becase of other duke post advice to do that if we see a fans that spins and stops , i did check current sense all resistors on u7000 they are ok

still nothing....

 

[geraymartha]

all i can think now is check all PGOODS and resitors? or maybe surrender jaja

 

[smiba]

This has nothing to do with PP1V5_S3RS0_CPUDDR, by removing this resistor to Q7950 the system will never make ALL_SYS_PWRGD good high resulting in the system never completing its power sequencing

Basically (with R7974 on the board) you will get ALL_SYS_PWRGD but the system is power cycling.

Bios area looking OK? U2800 area looking OK?
Resistance to ground (in Ohm) on PPVCORE_S0_CPU?

This could very well be a dead GPU as well, resistance to ground (once again in Ohm) on PPVCORE_GPU?

 

[geraymartha]

PPVCORE_GPU = 13.4ohm
​​​​​​PPVCORE_S0_CPU = 8.0ohm

u2800 area looks good , bios area looks good no red pobre points around

other detail is i removed some destroyed caps but i did not find shorts on those lines
C3701
C3730
C9710

the board was cleaned from other tec before i put my hand on it , he dont do soldering so im sure he did not replace anything
but he clean with paint tinner not ultrasonic.

i should try ultrasonic?

 

[dukefawks]

If the fan spins then ALL_SYS must be present and that also means 5V_S3 will be there. Go back and check your measurements.

 

[geraymartha]

i did re check is not there , fan spins and stops.
voltage is fluctuating.
i have no 5V_S3
i cant start all over again with readings {big mistake sorry i did want it to write : i can start all over again with readings , no i cant } , i want to find out if there is something that i can do because i have a pile of boards that do stuff like this now like 6 diferent models and i cant fix.

RTC is present
3V3_S5 is present
PPBUS_G3H is present
3v3_SUS is present
5V_SUS is present
5v_s5 is present
3.4v fo green l ight is present
ocilloscope lines look normal on clock circuit
there is no red probe points for extra clues
U2800 was replaced
i check current sense resistors

5V_S3 enable is not there

Fan dont spin do quarter fan

PPVCORE_GPU = 13.4ohm
​​​​​​PPVCORE_S0_CPU = 8.0ohm

Where do i go from here?
,

 

[smiba]

PP5V_S3 will be there but only for a split second until it power cycles again. Could very well be possible that your multimeter does not catch this
If the fan spins even for a split second it means you had ALL_SYS_PWRGD.

If you really believe there is no PP5V_S3, what is the resistance to ground in Ohms on this line?
With nowhere else to go you might just want to check the resistance to ground on all power lines, report back those with less then 100Ohm

 

[dukefawks]

The real question is does CPU Vcore pulse? If the fan moves all voltages are OK and the last one that needs to appear is CPU Vcore. Check carefully with a multimeter but the pulses are very short and on auto ranging meters pretty impossible to catch. Use a scope to see the pulsing.