Dell Inspiron 5567 (LA-D801P) turns on, and back off after a few seconds

[Seot]

The schematics are here: https://www.badcaps.net/forum/showthread.php?t=69873 .

So, long story short, some tiny bit of water damage, and some visible corrosion around UC5, QC2 and some audio controller. Removed some of the corrosion with alcohol, but still no luck.

So all in all, the laptop turn on (screen stays black), but fans and leds start, for about 10s , then goes back off. After a few turning ons, the indicator led beeps an error code, which stands for "CMOS battery failure". I checked with another battery and still fine. The original battery has 3.36V so it's also fine.

So I started checking some voltages, I have 3.3V, 5V, 19V VIN.

I tried to follow the power on sequence, from page 38 in the schematics but I don't quite understand it.

Any tips on how to proceed?
There's this EC MEC1404-NU, which supposedly all the signals are going through, it gets powered. Initially I thought the PCH_RSTRSM# signal might be the issue, because of the water damage area on UC5, and the signal was 3.3V when powered-off, but it's an active low line so that doesn't seem to be it.

Thanks. (will keep this updated)
(I should note that I'm currently in the process of studying electronics, so I've built stuff like voltage regulators, buck converters, so I have a basic understanding of how some of the components work, but it's still very much a WIP (i'm using the Art of Electronics book). I realised that I need to further my understandings at a lower level so I started studying electrodynamics from Morrin Purcell book first. I'm a programmer by trade, but never had a lot to do with electronics before, other than physics competitions).

[piernov]

Re: Dell Inspiron 5567 (LA-D801P) turns on, and back off after a few seconds

RSMRST# should be 3.3V. If it was low it would prevent the system from getting out of S5 state and reaching S0 state (where the fan can spin).
Just follow the power sequence to note voltage for each step. At least make sure you get CPU VCore and PLT_RST#.

[Seot]

Re: Dell Inspiron 5567 (LA-D801P) turns on, and back off after a few seconds

> Just follow the power sequence to note voltage for each step. At least make sure you get CPU VCore and PLT_RST#.

So my question is then: is there a time interval in which to check certain signals (i.e. do I need an oscilloscope?) or are they always on after the power button has been pressed ? (for instance PLT_RST#)?
Also, why are they passing signals like the PCH_PLTRST# and PCH_RSMRST# through AND-gates?(uc4, uc5) in the schematics.

Also, the UC4, the and-gate where I'm checking PCH_PLTRST# (which then gets transformed into PCH_PLTRST#_EC) is not even powered, even after I push the power-on button and the power led is on. So clearly the PCH_PLTRST#_EC (which I figure goes into the superIO chip/ MEC1404-NU) is not active. In the schematics, it should be powered by +3VS, so I think it should be powered after pressing the power button.

[Seot]

Re: Dell Inspiron 5567 (LA-D801P) turns on, and back off after a few seconds

Apparently, Intel's PCH documentation contains a wealth of information on all these signals and how they are driven: .

[piernov]

Re: Dell Inspiron 5567 (LA-D801P) turns on, and back off after a few seconds

+3VS is enabled by SLP_S3# on UZ3, so check if SLP_S3# is present, and check if +5VS is present as well (they both should be if the fan is spinning). And check if you get +3VALW on UZ3.
Those signals should be always present after pressing power button. So just checking with the multimeter after pressing power button is fine. Sometimes an oscilloscope may help but not here.
Before pressing power button the board is in an S5 state, and all G3H/S5 power rails should be present (not the same on battery so always use AC adapter). In the power sequence, it gets as far as RSMRST# being high, following is PWRBTN#, triggered by pressing the power button and it will tell the PCH to get out of S5, and then go to S4-S3-S0.

[Seot]

Re: Dell Inspiron 5567 (LA-D801P) turns on, and back off after a few seconds

Thank you very much for your help, piernov. (I've also recently stumbled upon your youtube videos, those were helpful as well to a degree, although only as general information, not directly related to the issue at hand).

So I don't have +3VS or +5VS out of UZ3, and since I've been running without the fan connected, I also on't have any fans. I used to have fans some time ago, but apparently they're not being powered on anymore.

So I realise that I need to do this troubleshooting more carefully, but now I've got enough knowledge about the interaction between the EC and PCH, and all the power rails, and have all the datasheets, it should be a straight-forward job (but will take some time for a beginenr like me).

So I'm checking again if the EC (mec1404-nu), is being powered on (VTR). It does get 3.3V.
So next step is to check if the SIO_PWRBTN# signal gets sent from the SIO (but first I need to read about this ME_SUS_PWR_ACK thing).
LE: So apparently no ME_SUS_PWR_ACK gets to the EC chip (if I read it correctly, I was sitting with the probe on it while powering it on).

So one level before that comes the PWROK signal. This is what I'll be checking now.

LE: Boy, I could really use a boardview for this board. The 0402 capacitors are not labeled on the board but are on the schematics. So I suspect the problem lies with missing RTCVCC supply to the PCH, due to the beep code the motherboard sends through the indicator led (mentioned in the first post), and that the tiny water damage is not far from some capacitors near the CPU+PCH package.

But I need to figure a way to test this.

[Seot]

Re: Dell Inspiron 5567 (LA-D801P) turns on, and back off after a few seconds

So as it turns out, +RTC_CELL is also connected to the SIO pin, and it is fluctuating heavily at a capacitor near pin #122, between 1.2 to 1.5V, so even more evince pointing towards this being the source of the issue.

The pcb track from the RTC_CELL is probably damaged somewhere, leading to some voltage drop.

LE. Actually, not really, after plugging in the AC, it is a steady 3.14V.

LE. One other interesting observation is that QC2, a MOSFET sending the PCH_RTCRST# signal has a 1.06V on its gate with AC on. The gate is supposedly connected to RTCRST_ON on the SuperIO/EC chip, but on that chip, the pin is 0V. So where is it getting that 1.06V from?

[Seot]

Re: Dell Inspiron 5567 (LA-D801P) turns on, and back off after a few seconds

It was my mistake, the MEC1404 chip also has 1.06V on its pin (which is a GPIO pin). So I wonder why that is. Theoretically it is below the Vol level, so the signal isn't asserted.

[piernov]

Re: Dell Inspiron 5567 (LA-D801P) turns on, and back off after a few seconds

RTCRST# and SRTCRST# are pulled up by the coin cell voltage since they must be always high. (same for INTVRMEN# and INTRUDER#) RTCRST_ON should be low to prevent RTCRST# from being asserted. This is most likely supplied internally by the EC, from its VBAT pin since it must be in the RTC well too.
When the computer is plugged in, the RTC well voltage should be taken from a 3.3V LDO. When the computer is unplugged and without battery, the coin cell supplies the voltage. I did not look search in the schematics, but usually a dual diode selects the input source. Therefore, the voltage on the RTC well should never be below 3V (except when AC adapter and battery are unplugged, and the coin cell is empty or disconnected).

[Seot]

Re: Dell Inspiron 5567 (LA-D801P) turns on, and back off after a few seconds

So that's 95% the issue. The PCH_RTCRST# is continuously being asserted ( and this doesn't let the initialization happen), probably due to the tiny water damage in the QC2 region. (that's the n-channel mosfet getting RTCRST on its gate).

There's a 20k 0402 resistor (rc78 in the schematics ) connected between drain, the PCH pin and rtc_cell. That resistor was also slightly affected by corrosion, and when I test it with my multimeter, it seems to be open.

I'll post pictures tomorrow. Today I did put some rosin in the area, to clean and isolate everything from air, but that obviously didn't help.

So I'll think more about this tomorrow, and maybe I'll replace that resistor. What's strange is that one of its pins is supposed to be connected to +RTCCELL, but I can't get that with the multimeter.

Piernov, again, your contribution was very valuable. Thanks. (Maybe you should set up a.patreon page).

(And as a side note, today I was recycling a few 0402 resistors from some old mobos, and I dropped some on the ground. I never found them again, the things are like dust specs.)

[piernov]

Re: Dell Inspiron 5567 (LA-D801P) turns on, and back off after a few seconds

If RTCRST# is low the PCH won't work at all, the board will stay in the S5 state and SLP_S5#/SLP_S4# will not come up.
You should get approximately 3.3V at both sides of RC78, it's the pull-up resistor. Check at RC77 as well. If replacing RC78 doesn't solve the issue, QC2 may be dead, you can take it out and see if the voltages come back as they should be (it may even work without it).
Also since it's water damage, look closely to see if the pads on the components are not corroded and they are making contact.

Yeah 0402 are small, but 01005 is where it gets really hard, on iPhone boards for example. Without a microscope it's almost impossible to work with them…

PS: no patreon (2 people contributing 2€ isn't worth it), but I've got a paypal.

[Seot]

Re: Dell Inspiron 5567 (LA-D801P) turns on, and back off after a few seconds

So indeed, Rc77 has 2.97V on one pin and 2.87 on another. (With the ac on, 3.14v).

Rc78 still nothing. I will replace it and update here (probably will only get around to doing that tomorrow).

[Seot]

Re: Dell Inspiron 5567 (LA-D801P) turns on, and back off after a few seconds

So, only today have I really got around to replacing that resistor, and despite some encouraging signs, still no cigar. (I first had to practice smd soldering and other things got in the way).

So it's back in the original state, fans spinning, it beeps the error code for no memory. After inserting memory it looks like it's going to boot, but stops with the error code "CMOS battery failure", as before.

So this operation clearly fixed some things (fans among other things), but it's still not working.
Also, now I have 2.95V on RC78 as well.

[Seot]

Re: Dell Inspiron 5567 (LA-D801P) turns on, and back off after a few seconds

And now, for some strange reason, it works. I haven't put it all back together, but I turned it on again, and the error code was "Bad LCD", while the screen was unplugged. So I plugged the screen in, and I had an image.

I'm not 100% sure it works, but I had something on the screen, which I didn't before. So I'll put it back together and report back.

[piernov]

Re: Dell Inspiron 5567 (LA-D801P) turns on, and back off after a few seconds

About the CMOS battery failure code, it caught me as well. Had to unplug the CMOS battery, plug it back in and eventually it worked.
If it works now, I guess it's all good. Good job!

[Seot]

Re: Dell Inspiron 5567 (LA-D801P) turns on, and back off after a few seconds

It works just fine. I'm writing from it right now.
The issue hasn't occurred anymore, so I assume plugging in the main battery solved the problem completely.

Thank you again, piernov, your help was instrumental. (maybe I'll make up for this one day).

[Madhusha]

Re: Dell Inspiron 5567 (LA-D801P) turns on, and back off after a few seconds

any body know howto program mec1404-nu ????

[vedoza]

Re: Dell Inspiron 5567 (LA-D801P) turns on, and back off after a few seconds

It works just fine. I'm writing from it right now.
The issue hasn't occurred anymore, so I assume plugging in the main battery solved the problem completely.

Thank you again, piernov, your help was instrumental. (maybe I'll make up for this one day).

hi brother

I encountered the same problem
POWER_SW # _MB 3.3 v no problem
I changed the rtc battery
I'll be glad, if you help me