Asus Prime Z270-A shuts down

[xebbmw]

Hi all,

I started looking into motherboards repair after watching lots of videos on dicky96's channel. Thanks for your work!

I have this Asus Prime Z270-A motherboard with the following symptoms: motherboard will turn on, then it executes its own tests, passes CPU and DRAM and then shuts down by itself. It is doing it no matter if memory module(s) are inserted or not. I checked for shorts, but I could not find any. I checked VCORE = 0.9V, but it shuts down itself very quick so really impossible to check for other voltages.

I was reading on the web that this symptom might has something to do with a corrupted firmware. So I desoldered the flash chip 25Q128A and I tried to read it with CH341A programmer. But I can't read it, the chip does not return any ID (I cannot test my 1.8V adapter, I am not sure if it is working correctly or not; although I tested the programmer with another 3.3V chip and I get good results). Thus I assume it is faulty, I will try to order a new one.

Also once the motherboard shuts down, I cannot power on again using the regular power button. I have to shut down the power supply from the button, then turn on power supply and then turn on motherboard from power button.

If there are people more experienced with such symptoms, I would like to confirm the following:

1. Should I assume that all voltages are there if the motherboard reaches its own tests, as it passes CPU_LED and DRAM_LED tests? (I have the repair guide for Z270-A but without boardview it is rather difficult to identify for signals).

2. A faulty flash chip would shut down the motherboard? Or could be some other issues with the board.

Thanks!

[RJARRRPCGP]

Re: Asus Prime Z270-A shuts down

Sounds like it's activating thermal shutdown or it shorts the PSU.

[xebbmw]

Re: Asus Prime Z270-A shuts down

Ok, I did further tests. As I mentioned I removed the flash chip and now when powering the board, CPU fan spins a bit, then turns off and then turns again on and ... then no more shutdown.

First I checked for any sign of shorts on USB connectors but there are none. Further from the power supply connector, I checked +12V, +3.3V and +5V and all are fine.

Then I was able to measure some voltages: VCORE = 0.936 V. There are two other coils on the upper part of CPU and these have 1.097 V (not sure what are these for).

I got some instructions (from another website) how to measure DDR4 voltages. And these are showing as follows:
VDD - 76 = 1.209 V
VTT - 77 = 0.597 V
VREF - 145 = 0.604 V
VDDSPD - 284 = 3.393 V
VPP - 288 = 2.501 V

I tested PCH chip, in one of the corner there is 3.3V (after removing the heat sink). I did not keep it long without heat sink, the chip becomes warm, not hot. The heat sink has a kind of rubber for heat transfer, this looks fine without wear.

Also the CPU get warm, not hot. Thus I assume everything should be fine from CPU side, this gets supplied with the required voltages.

Let me know if you have any other ideas.

[szdnkx]

Re: Asus Prime Z270-A shuts down

You'd better find the drawing of the motherboard.
Find then signal named shutdown#
It often controls then Temperature
Remove the triode of this control signal

[DynaxSC]

Re: Asus Prime Z270-A shuts down

This should help you. It's not the same, but should be very similar.



Check if you have a TPM header, if yes get a boot code debug card like TL611PRO on Ali, look for the last bootcode which is displayed before restart. This might narrow down the search.
Sometimes there is only a place for the pinheader for TMP module, then you need to McGuyver a pin header there (deisolating the pads, drilling & soldering necessary).
You may put the boot code card also into a PCIe x 1 slot, but it not always work there.

LINK to boardview https://www.badcaps.net/forum/troubl...boardview-need

[anikin73]

Re: Asus Prime Z270-A shuts down

as you had said, it shut down when it is doing ram checking. you should be checking on DRAM slots for missing voltages....or signal. If i am you, i clean up the ram slot first...

also i check pcie x1 slot at a13 whether there is a 3.3v reset signal. this signal will only appear when all critical voltage appear.

a damaged program in bios will shut down the system.

[anikin73]

Re: Asus Prime Z270-A shuts down

pin a11 should be the reset signal. I realise in your case, there could be 3 possible things happening.
1) one of the chips when power up shorted.
2) bios corrupted.
3) PCH issue causing shutdown.

[DynaxSC]

Re: Asus Prime Z270-A shuts down

Try to boot only with one DRAM module, in all 4 slots one after the another.
Try another RAM stick brand, sometimes some RAM's are not 100% compatible.
If you manage to boot try to increase RAM Voltages, this might help if rams not fully supported.

[xebbmw]

Re: Asus Prime Z270-A shuts down

Hi all,

Thanks for your reply, I worked more on the board and here are my latest findings.

It seems that around the flash chip W25Q128A I am missing some resistors, the missing resistor pads are square and shows a bit of solder compared to others that are showing round and flat. These are shown F1R16 and F1R15 in the attached schematics which is coming from a Asus Prime Z390-A R1.02 board. These resistors are also showing with the same ID in the attached boardview Asus STRIX Z270E GAMING R1.02A.

I ordered some 0402 resistors for the moment, I am waiting for them to arrive. Once I have them I will try to install them.

I do not have a debug card, I ordered once from Aliexpress but it never arrived.

I will keep you posted when I have more news.

LINK to boardview https://www.badcaps.net/forum/troubl...ew#post1834572

[SMDFlea]

Posted link to boardview

[pavski]

Thanks for posting this, have you managed to solve the problem? I have something similar, the board starts, then stops after a second, then tries to start again and nothing happens.

After resetting CMOS I have managed to get to BIOS but after a minute or so it froze.

Could this be corrupted BIOS or something wrong with BIOS power supply?

BTW I cannot locate this 25Q128A chip on the board, do I need to remove a heat sink to find it?

[DynaxSC]

Missing meaningful parts around bios chip is very unlikely, as the boot process starts normally. I'd suspect mostly a corrupted Bios. Backup the current Bios and program a stock bios by hw programmer, eg ch341. If the board will boot correctly, you will need to reconstruct the Bios NVRAM and Gbe regions, provided the NVRAM and Gbe regions in original Bios are not corrupted. Gbe contains the LAN MAC address, NVRAM contains all personalisation data of the board, eg. UUID, serial number, and many other stuff. A default MAC in the stock Bios might make Windows networking not working fast and stable so this is essential to be restored. The rest is not mandatory for such an old board (might make it impossible to register the board on ASUS site). MAC, serial, UUID may be also found on stickers on the board or on the board case.

Could also be a bricked/missing Management Engine in the PCH. On Asus boards programming the first=oldest available stock Bios might restore the ME back into the PCH.

BTW the Bios chip must be somewhere in the pcb quarter where the PCH is, look carefully, it might be under the PCH cooler or somtimes at the board edge or even under the pcie slot locker. Vendors sometimes deliberately put them in difficult to solder places, eg. hidden under the pcie slot locker, or very close to pcie slot, making it difficult to desolder with hotair, or access with a clip to read/write in-circuit the Bios by hw programmer.

[pavski]

Thanks for the info, after a few attempts I have managed to go to the bios and flash it using Asus tool. Things slightly improved, but the board is still temperamental.

Sometimes it doesn't boot, sometimes it does, but soon after window blue screens appear with different errors.

On occasion, the board works perfectly, and I can use windows for a few hours without any issues.

I'm pretty confident that this is a hardware issue

I thought this may be related to the temperature, the board seems to work better after a few booting attempts when presumable is warmer.

I have bought a freeze spray for electronics and tried to freeze some parts of the board, hoping to pinpoint the problem but was not successful, the board is too volatile for it to work (like worming it will not improve things, etc.)

Any ideas what might be wrong to explain this weird behaviour?

[DynaxSC]

This is the kind of failure probably most difficult to trace.

But sometimes we tend to look for a very complicated reason, but maybe this is something very simple ?

Have you tried to clean the LGA pins and processor pads?

Have you tried to clean the momory sockets and memory pads?

Have you a GPU installed? If yes did you try to run Windows with another GPU, or without GPU provided your processor has an IGPU (if your processor does not have an IGPU, you can run the machine without an GPU at all, and acces the GUI with remote desktop from another machine in the same network address space, remote desktop access must be enabled first) ?

Did you try other processor and other memories ?

What else you could do is to play a little bit with BIOS settings, eg. supply voltages / power plans for processor, memory controller, memories, PCH etc. Sometimes altering these one by one may change the board behavior/stability, what will indicate where is the problem. Altering can be done as well as lowering, or increasing the voltages in small steps, effect can be: no effect, improving stability or reducing stability. Maybe worth to try.
Once I had a board, which did not like to boot very reliably. Increasing memory supply voltage by 0.05V compared to default solved the issue.

The BIOS is relying on the SIO, CPU VRM and maybe other VRM's in terms of measuring most important voltages on the board, and dependent on the readings is correcting the voltages to nominal. But SIO/VRM's may have or have resistor voltage dividers between the power line and VIN measuring input. These dividers can be unprecise, so you get significant measuring error, so the output voltage will have the same error difference. Eg. SIO will read 1.05 as PCH supply voltage, and in reality there will be only 1.00V or 1.10V.