820-3437 PP3V3_SUS pulsing

2click

Member
Hi, I have this board with a pulsing PP3v3_SUS @1,0-1,3v. U8020 and PP3V3_S5 and P3V3SUS_EN voltages are present and stable, changed U8020, no change... what can be causing this behavior? Any experience like this?
when I heat the pch a little it turns on... should I reflowit with flux?
 
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2click

Member
PP3v3_SUS = .530 (diode mode)
when removed F7140 PPBUS_G3H is 8,6
when F7140 in place PPBUS_G3H is not stable (aprox every 5 seconds varies from 8,6v as low as 8,10v)
Removed R5450 and PPBUS_G3H stays stable, when in place PPBUS_G3H gets unstable again
 
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2informaticos

Administrator
Staff member
Put back the resistor and check if board stays on in SMC bypass mode.
Check resistance between pins 17/18 and 27/28 of U7100.
Check for short on big coils from secondary power supplies.
 

2click

Member
now it is not turning on in smc bypass and was checking S4_PWR_EN and PM_SLP_S5_L is pulsing too...
SMC_PM_G2_EN is going low every 5 seconds guess thats why I can´t get stable voltage on secondary rails

coils diode mode
L7310= ,049
L7320= ,049
L7630= ,129
L7430= ,156
L7560= ,357
L7520= ,430
L7130= ,138
L3895= ,522
L7701= ,427

I don´t have a clue what is making PPBUS_G3H unstable... please help me!...
 
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2informaticos

Administrator
Staff member
I suppose SMC_PM_G2_EN varies at same time with PPBUS_G3H; check what happens with 3V42_G3H.
When the board stopped to stay on in SMC bypass?
What was the last thing you've done before that?
 

2click

Member
If I leave the PSU on, the board turns on after around 60 seconds @,300A and goes down to ,160A. CPU is not getting warm... no chime
 

2click

Member
when it turns "on", the pulsing on ppbus is gone and all the voltages that where pulsing stay stable... I´ll make the list of the rails present and let you know...
 
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