Nuvoton NCT5535D SIO

[прямо]

Hi guys, I have an ASUS P8H61-MX USB3 motherboard that can't turn off the power supply because the PSON signal generated by the SIO chip always goes back to and stay at low state (below 5V) half a second after it went to high state (5VSB)

Also worth mentioning that the PSON signal will randomly switch to low state and therefore turning on the power supply and the computer as if a ghost has pressed the power button 🤣

The SIO chip is Nuvoton NCT5535D. Can't find a datasheet for it, only for NCT5532D (more or less the same though, just different pinout)

Is the SIO faulty?
Can it be replaced?
Do I need to program the replacement IC?

[DynaxSC]

Re: Nuvoton NCT5535D SIO

Hi, generally a quite difficult problem to diagnose. You can naturally replace the chip w/o any problem, but it must not be the reason for the failure. Programming is not needed.

But check first the PWRBTN circuit, if there is no cap getting shorted, and you should check whether the VIN voltage monitoring inputs of the SIO have stable voltages when mobo is running. A drop/unstability on these lines will trigger the SIO to power off ATX power with PSON. Check also stability and right voltage of the SIO power.

I can check if I can get a boardview for you, which board revision do you have ?

[прямо]

Re: Nuvoton NCT5535D SIO

I already have the boardviewer file because previously it had a USB device over current issue. I wasn't able to solve it on the hardware level. Checked the USB OC detection voltage (ok), voltage divider resistors also ok, also tried removing the ESD protection diodes then fuse one by one, no joy. Decided to hack the BIOS to ignore USB OC.

Anyway, that's the old story. The behavior that I'm still getting from this board is as I explained in my previous post. It will randomly turn on the power supply and the fans, but the board doesn't post and boot into Windows until I press the power button.

When the board is running, all voltages are stable. I left it on for 24/30 days test mining and played some AAA games, never crashed, never hang up on me.

I gave it to my niece. I still would like to be able to solve the random turn on issue though. Thought maybe it's related to the Nuvoton SIO, but with Aliexpress being banned from exporting goods to this country, I suppose that ship has sailed. No way of getting any replacement chip whatsoever, not anytime soon.

[DeXXter]

Re: Nuvoton NCT5535D SIO

Hi, generally a quite difficult problem to diagnose. You can naturally replace the chip w/o any problem, but it must not be the reason for the failure. Programming is not needed.

But check first the PWRBTN circuit, if there is no cap getting shorted, and you should check whether the VIN voltage monitoring inputs of the SIO have stable voltages when mobo is running. A drop/unstability on these lines will trigger the SIO to power off ATX power with PSON. Check also stability and right voltage of the SIO power.

I can check if I can get a boardview for you, which board revision do you have ?

Is it really not needed to program? I have an asus h81m-k board that I wanted to replace the pch, but also found out that the 3v line is like 8ohm, and is the nuvoton ec that gets hot. I found the replacement, quite cheap, but Idk if just replacing will solve the issue. Thanks in advance.

[DynaxSC]

SIO's don't need to be programmed, u can replace it as is. On more complex mobos they may have an small external eeprom attached, but this is no issue, as long as it is not demaged. Pay attention to make the tin good liquid when taking off the SIO, its very easy to rip off the pads.

[DeXXter]

SIO's don't need to be programmed, u can replace it as is. On more complex mobos they may have an small external eeprom attached, but this is no issue, as long as it is not demaged.

Nice, thanks for the answer, already ordered the replacement.