820-3435 Missing ALL_SYS_PWRGD

[ALB-Repairs]

I have a 3435 board here im working on thats got me stumped. It is missing ALL_SYS_PWRGD, All power rails required for ALL_SYS_PWRGD are present
However PP1v05_S0 is lower than it should be. it is only making 0.95V for some reason. I have replaced the feedback resistors and the IC. checked all resistors and i cant figure out why its output is lower than a known good board!

 

[dukefawks]

Removing R8164 should bring or at least start pulsing ALL_SYS. Is 1V05 resistance to GND low?

 

[ALB-Repairs]

Removing R8164 should bring or at least start pulsing ALL_SYS. Is 1V05 resistance to GND low?

It is not low resistance to GND.

I have had ALL_SYS_PWRGD come up a couple times after messing around (and even got 1v05 up at some point temporarily) but it seems to be related to the heat of replacing random components. When 1v05 came up so did ALL_SYS_PWRGD, but it never actually posted. The current draw was doing wierd stuff, fan would start-stop, start, current would stick at 0.3A with all rails, then after 20 seconds would jump to 0.55A and then 0.7a and back down to 0.55

Im not even sure what it was i did to get the 1v05 up correctly but its gone since i cleaned the flux off properly. Im stumped.

 

[dukefawks]

So no 1V05 at all right now? Any other rails present?

 

[ALB-Repairs]

So no 1V05 at all right now? Any other rails present?

ahh, sorry i was unclear, it dropped back to 0.95. al other rails there but v-core.

 

[dukefawks]

Remove R8164 and see if at least ALL_SYS will come up so you can be 100% sure we are looking at the correct problem rail.

 

[ALB-Repairs]

Remove R8164 and see if at least ALL_SYS will come up so you can be 100% sure we are looking at the correct problem rail.

Yes, ALL_SYS_PWRGD comes high if R8164 is removed.
Fan spins up twice, V-Core present.ect No post

 

[dukefawks]

Must be around U7600 then. FET also replaced? Check the VREF and VTTREF lines, leaky cap pulling them down?