820-00923-A S0 state, no All_SYS_PWRGD

Naevius

New member
I have a 820-00923-A board that gets into a S0 state, but no fan spin or image. Since I can't find the correct schematic and brd I'm using the 820-00239 one, seems to work ok with this board.

The board takes about 0.77A and CPU is getting hot, so seems to boot. I'm not getting All_SYS_PWRGD tho.
Some measurements:

PP3V0_G3H = 3V
PPVCC_S0_CPU = 1.098V
PP0V6_S0_DDRVTT = 0.6V
PP1V8_S0 = 1.8V
PP1V2_S0SW = 1.2V
PP1V0_S0SW = 1V
PP5V_S0_T139 = 5.12V
PP5V_S0 = 5.12V
PP3V3_S0 = 3.33V
SMC_PM_G2_EN = 3.4V
PM_PCH_PWROK = 3.31V
PP3V3_PMICLDO = 3.29V
PPBUS_PMIC = 13.03V
CPU_VCCST_PWRGD = 0.999V
S5_PWRGD = 3.25V
SMC_DELAYED_PWRGD 3.4V

Those rails look fine to me, still U7800 it not turning All_SYS_PWRGD on.

No visible liquid damage. I kind of suspect U7800, but the area around that chip looks just fine.
 

JohnB8812

New member
I?m pretty sure it?s not possible to have VCore but no ALL_SYS...double check that. Do you get any external video?
 

2informaticos

Administrator
Staff member
Recheck ALL_SYS_PWRGD signal.
Strange to get complete power sequence without it...

Check for USB activity and external video.
 

Naevius

New member
Rechecked ALL_SYS_PWRGD, still not present (0.0V). Tested on both R7103 and R7805

Also checked PP5V_S0_VCORE1/2, both are 5.12V.

No external image. Can't test USB activity since this board doesn't have actual USB-B connection, and I don't have a USB-C>USB-A convertor

I am noticing that if you leave power on for a while, and the CPU is getting really hot the fans start spinning. But no fan spin when you apply power to a cooled board

[edit]
I did find a USB-C->A convertor, but no USB activity it seems (tested with a USB drive with a flashing LED, no light at all on the USB drive)
 
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JohnB8812

New member
PP5v_S0_VCORE is not CPU Vcore. PPVCC_S0_CPU is Vcore. I'm assuming that is missing due to no ALL_SYS, but if the CPU is getting hot with no VCore, this is bad and probably a dead CPU.
 

Naevius

New member
PPVCC_S0_CPU is 1.098V as stated in my first post.

So apparently it's not surposed to get PPVCC_S0_CPU without ALL_SYS_PWRGD? Is it possible there is a line break in the ALL_SYS_PWRGD line, so U7800 is actually outputting voltage on ALL_SYS_PWRGD to the CPU, but not to other parts of the system? Would not be easy to check I guess

[edit]
Let's say just for testing purposes I manually wire 3.3V to ALL_SYS_PWRGD on R7103 or R7805, can something go wrong? Can I break more than already is?
 
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2informaticos

Administrator
Staff member
Is R7805 good?
Even if you get VCORE, missing ALL_SYS_PWRGD is "letal".
This denotes a PCH issue, as it shouldn't enable VCORE in this case.
 

Naevius

New member
Checked R7805, is 10k as it should.

So is it certain that it's a PCH issue? This pretty much makes the board unrepairable, right?
 

2informaticos

Administrator
Staff member
Do you get 3V at pin 1/R7805?

ALL_SYS_PWRGD is controlled by U7800 in this model.
It monitors other power rails and power good signals.
 

Naevius

New member
Yes, 3.3V on pin 1/R7805, but 0V on pin 2. So U7800 is very likely pulling it down.

On page 74 of the schematic it seems all the required voltages are present to enable ALL_SYS_PWRGD, even though I find this type of diagram kind of confusing, since it's not always clear what is an input or output. Would replacing U7800 still be a possible solution?
 

2informaticos

Administrator
Staff member
Should be U7800, but you cannot be 100% sure.
Internal damage on SMC can cause that too.
If you can cut off the trace for U7800, you can see which chip pulls down the signal.

Reflow U7800 with good flux.
Maybe bad contact for one supervised voltage...
 
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