[SOLVED]820-2936-B ALL_SYS_PWRGD problem

[macfix]

Hello Everybody

First problem is no PPBUS_G3H replaced U7000, Q7080,Q7085 , PPBUS_G3H come back but fan doesnt spin. After check voltage , I didn't see PM_SLP_S4 so dedicate replace U1800 and bingo!! PM_SLP_S4 come back and S0 rails come . But now no CPU Vcore enable
When checked cause see ALL_SYS_PWRGD signal isnt there... Injected ALL_SYS_PWRGD line 3v CPU VCore comes,fan spin and usb mouse light is ok but no internal and external screen

So i thing first problem is ALL_SYS_PWRGD why isnt there... measured Q7950 around all voltage is ok. replaced Q7950 nothing change.

Any idea for next step...

Thanks

 

[aprendiz]

If ALL_SYS_PWRGD is never present a secondary power supply is not comming high, keep injecting voltage on ALL_SYS_PWRGD and check for the missing voltage...
ALL_SYS PWRGD does not come from Q7950 but from R7967!!! (pull up resistor)
You have replaced PCH so now you need to reprogram bios with a clean ME region....

 

[macfix]

Thank you for answer aprendiz . My board is BJT version so u7960 place is empty ( i ll check R7967 not sure) .
Also measured power rails when injecting fake ALL_SYS_PWRGD, only T29 line 0 volt but I know this line for thunderbolt so if i didnt connect anyting this port its will be off...is it corect? T29 line must be any voltage when port is empty ?

 

[arghhh]

yes 10 char

 

[dukefawks]

There must be a voltage rail missing, find it. Also you replaced the PCH so now the BIOS must also be flashed with a clean ME!! Only needed after you get it to work of course.

 

[macfix]

Thank you dukefawks but voltage is looking fine.Only T29 rail is 0V but i didn't find any connection about ALL_SYS_PWRGD

And one note: when checked to ALL_SYS_PWRGD to ground resistance 1Kohm ( some time 0.5KOHm) at this board but known good board this resistance is 15KOhm is it problem ?

 

[dukefawks]

A bunch of PGOOD signals are connected through resistors. Remove them and see when that 1K goes up. R7965-68 etc.

 

[macfix]

thanks you everybody, after replace SMC all_sys_pwrgd turned back ( maybe wrong smc soldered board before come my desk). What ever now board is working without problem.