Acer Aspire E5-772G fails to reach ALL_SYS_PWRGD

[shortcut7000]

Hi everyone,

I have an Acer Aspire E5-772G with mainboard: Wistron Brook BH 14276-1M
Schematics are in this post: https://www.badcaps.net/forum/showpo...82&postcount=2
Boardview .brd file I found here: https://drive.google.com/file/d/15-n...Kw6L76hDj/view

The laptop is not powering on.
When pressing the power button, the power LED quickly flashes once and then goes off.
System seems to try running the power up sequence for 10 seconds getting stuck at step 6 [1.05V or 1.5V rail] before reaching S0 state (schematics sheet 102), then turns off.

What I did so far:

Initial checks:
- Charging circuit is working. Battery is charging until full.
- 19V power rail present; 1st/2nd mosfet + current resistor all ok

Config for testing:
- Battery removed
- RAM removed
- SSD removed
- all peripherals + display disconnected
- Bios battery present and full
- Chassis switch pressed
- Lid switch (Hall sensor) is high (= lid open) and working

Current draw:
Current draw when power adapter plugged in = 2 mA
Current draw after PWRBTN pressed = 23 mA (for ~10 seconds, then back to 2 mA)

Check test points (schematics sheet 89):
AFTP1 (3D3V_S0) = 1 pulse after PWRBTN
AFTP7 (3D3V_AUX_S5) = 3.29V always
AFTP8 (3D3V_S5) = 3.39V after PWRBTN for ~10 seconds, then off
AFTP9 (5V_S5) = 5.15V always
AFTP10 (PM_PWRBTN#) = 3.39V after PWRBTN for ~10 seconds, then off
AFTP11 (H_CPUPWRGD) = 0V always
AFTP12 (S5_ENABLE#) = 3.25V after PWRBTN for ~10 seconds, then off
AFTP13 (PLTRST#_PCH) = 0V always

PGOOD signals:
PU4501 (3.3V & 5V regulator) = 3.25V after PWRBTN for ~10 seconds, then off
U4601 (TPS51624_CPUCORE) = 1 pulse after PWRBTN
PU4801 (1.05V_VTT_PWRGD; pin10) = 1 pulse after PWRBTN
PU4801 (PWR_1D05V_VDDQ; pin5) = 1 pulse after PWRBTN
PU4901 (RT8231 for VDDQ 1.35V) = 0V always
PU8501 (RT8812A_VGA_CORE) = 1 pulse after PWRBTN
PU8601 (RT8231 for VGA VDDQ 1.5V) = 0V always

Other checks:
PM_RMSRST# = 3.25V after PWRBTN for ~10 seconds, then off => normal
RTC_RST# = 3.12V always => normal
LOWBAT# = 3.39V after PWRBTN for ~10 seconds, then off => normal
PM_SLP_S3# = 1 pulse after PWRBTN
PM_SLP_S4# = 1 pulse after PWRBTN
ALL_SYS_PWRGD = 0V always

So it looks like BIOS and EC are working fine.
I checked all coils and caps around the power regulators. Everything seems ok.

Any ideas what could be the problem or what to do next?

Thanks so much for any hint!

[mcplslg123]

Re: Acer Aspire E5-772G fails to reach ALL_SYS_PWRGD

It could be PCH dry solder. Put a lot of flux around PCH and gently heat it up around the PCH and not on top of it.

[piernov]

Re: Acer Aspire E5-772G fails to reach ALL_SYS_PWRGD

PU4901 (RT8231 for VDDQ 1.35V) = 0V always

Should pay attention to that before messing with the PCH.

[shortcut7000]

Re: Acer Aspire E5-772G fails to reach ALL_SYS_PWRGD

Thanks guys for the swift responses! Really amazing how reactive this forum is!

And yes, I would like to rule out everything else before trying a reflow.

Being not an expert, I am not completely sure if I understand the power sequence in the schematic correctly.
To me it looks like 19V, 5V and 3.3V are all fine and it must indeed be something going wrong when trying to enable the 1.35V or 1.05V rails.

I will try to investigate a bit more around PU4901 when I am back on Thursday.

Will keep you posted...

[shortcut7000]

Re: Acer Aspire E5-772G fails to reach ALL_SYS_PWRGD

Ok, I did some more research on PU4901 (1.35V regulator) and PU4801 (1.05V regulator).
The voltages are as follows:

PU4901 (1.35V)
pin1 (GND) = GND
pin2 (PWR_VTT) = 1 pulse after PWRBTN
pin3 (GND) = GND
pin4 (PWR_VDDQ_VTTREF) = 1 pulse after PWRBTN
pin5 (PWR_VDDQ_SENSE) = 1 pulse after PWRBTN
pin6 (PWR_VDDQ_FB) = 1 pulse after PWRBTN
pin7 (PWR_VTT_EN) = 1 pulse after PWRBTN
pin8 (PWR_VDDQ_EN) = 1 pulse after PWRBTN
pin9 (PWR_VDDQ_TON) = 18,25V in standby / drops shortly to ~12V on PWRBTN
pin10 (RUNPWROK) = 0V always (!)
pin11 (PWR_VDDQ_VCC5) = 5.15V always
pin12 (PWR_VDDQ_VDDP) = 5.15V always
pin13 (PWR_VDDQ_CS) = 1 pulse after PWRBTN
pin14 (GND) = GND
pin15 (PWR_VDDQ_LG) = 1 pulse after PWRBTN
pin16 (PWR_VDDQ_PH) = 1 pulse after PWRBTN
pin17 (PWR_VDDQ_HG) = 1 pulse after PWRBTN
pin18 (PWR_VDDQ_BOOT) = 4.69V in standby / 5.15V pulse after PWRBTN
pin19 (PWR_VDDQ_VTTIN) = 1 pulse after PWRBTN
pin20 (PWR_VTT) = 1 pulse after PWRBTN

PU4801 (1.05V)
pin1 (GND) = GND
pin2 (UNCONNECTED) = not connected
pin3 (GND) = GND
pin4 (PWR_1D05V_VTTREF) = 1 pulse after PWRBTN
pin5 (PWR_1D05V_VDDQ) = 1 pulse after PWRBTN
pin6 (PWR_1D05V_FB) = 1 pulse after PWRBTN
pin7 (PWR_1D05V_S3_EN) = 0V always
pin8 (PWR_1D05V_S5_EN) = 1 pulse after PWRBTN
pin9 (PWR_1D05V_TON) = 18,25V in standby / drops shortly to ~12V on PWRBTN
pin10 (PWR_1D05V_PG) = 1 pulse after PWRBTN
pin11 (PWR_1D05V_VID) = 5.15V always
pin12 (PWR_1D05V_VDD) = 5.15V always
pin13 (PWR_1D05V_CS) = 1 pulse after PWRBTN
pin14 (GND) = GND
pin15 (PWR_1D05V_LG) = 1 pulse after PWRBTN
pin16 (PWR_1D05V_PH) = 1 pulse after PWRBTN
pin17 (PWR_1D05V_HG) = 1 pulse after PWRBTN
pin18 (PWR_1D05V_BOOT) = 4.69V in standby / 5.15V pulse after PWRBTN
pin19 (VLDOIN_1D05) = not connected to anything
pin20 (VTT_1D05) = not connected to anything


So, it looks like the RUNPWROK signal from PU4901 (1.35V) is not there.
Does this mean PU4901 is broken and PCH is fine (hopefully)? Is there any way to check this?
The two mosfets and coil on the VDDQ power line seem to be ok. No short to ground or something. Do I need to have the RAM installed for the RUNPWROK signal?

For the moment I will not touch the PCH...anyway scared of this, since it comes in the same BGA package as the CPU...

Thanks for any further hint!

[shortcut7000]

Re: Acer Aspire E5-772G fails to reach ALL_SYS_PWRGD

Ok, some progress here, but no good news:

First I replaced PU4901 which resulted in a completely dead laptop.
Then I realized that PU4902 (one of the mosfets of the 1.35V rail) got killed (shorted). I replaced it.

Then some success: the power LED stayed on after pressing the power button and after a while the fan started spinning full speed. Battery was charging. However, no display and AFTP11 (H_CPUPWRGD) still 0V always.

After some powering on and off I am now back to the same situation as in the beginning. Power button only gives one pulse of the power LED.
In addition I do now have a short to ground behind the 1.35V coil PL4901.

I guess that is bad news, right?

[shortcut7000]

Re: Acer Aspire E5-772G fails to reach ALL_SYS_PWRGD

I tried now to isolate the short to ground behind coil PL4901.

I opened the jumpers PG701-706 and unfortunately the short is on the side towards the CPU. To be specific: 1D35V_CPU_VDDQ_S3 is shorted to ground.

Does anybody know if there is still a small chance that this CPU is not dead and how to find it out? There are still some caps on that side, but I did not yet dare to do any voltage injection to check them. Also I am not quite sure if injecting such a low voltage would result in any component heat up at all.

Any last words from the experts? :-)

(just for learning purposes I would also be interrested if there is anything I obviously did wrong on the way...)

[mon2]

Re: Acer Aspire E5-772G fails to reach ALL_SYS_PWRGD

What is the resistance to ground of the suspected CPU rail?

No power. Meter in the lowest resistance scale to measure.

[shortcut7000]

Re: Acer Aspire E5-772G fails to reach ALL_SYS_PWRGD

Hey, thanks for keeping this thread alive!

The resistance to ground of 1D35V_CPU_VDDQ_S3 is almost 0 Ohm. It is the same as holding the multimeter probes together.

As a reference I also measured the resistance of 1V_CPU_CORE which is around 1 Ohm which should be normal.

Thanks!

Edit: Actually, what I suspect is the following: Since mosfet PU4902 got shorted after raplacing PU4901, the 1.35V rail might have seen the 19V_DCBATOUT which probably killed the CPU. But I do not want to believe it yet...

[piernov]

Re: Acer Aspire E5-772G fails to reach ALL_SYS_PWRGD

1 ohm to ground is way too low on Haswell-U/Broadwell-U.

[shortcut7000]

Re: Acer Aspire E5-772G fails to reach ALL_SYS_PWRGD

Thanks piernov,

indeed, I just read it on the logiwiki. So I guess the CPU gave up after all (or I killed it). That is very sad.

I think I will just still measure around a bit and then slowly let it go...

Thanks anyway for all your help!