Asus X450LC no power (no PM_SLP_S4#)

[piernov]

Hi,
I don't have the laptop anymore, but I tried to diagnose an Asus X450LC this morning.
At first, the power LED would light up after pressing power button, but nothing happened.
I traced this back to a missing PM_SUSC# signal (PM_SLP_S4# coming from the PCH).
PM_RSMRST# was present, there was 3.3V on the power button.
I tried to flash the BIOS, same thing but now the power LED wouldn't even light up after pressing power button. Restored to the original BIOS, still no power LED.
I didn't have the time to check any more than this, I especially didn't check the RTC circuit but since RSMRST was present, I hoped (probably wrongly) it was ok. The CR2032 was at 3.1V though, so it's ok.

If anyones has an idea… It does not really matter anyway, the owner will probably replace the motherboard, but this still had me confused.

Original BIOS, repair guide and boardview attached.

Link to boardview & repair guide - https://www.badcaps.net/forum/troubl...d-repair-guide

[caspian]

Re: Asus X450LC no power (no PM_SLP_S4#)

it is possible that the SIO got damaged during your measurements, as it happened to me before.

[piernov]

Re: Asus X450LC no power (no PM_SLP_S4#)

I didn't measure on the SIO pin's directly, and the change in behaviour happened just after the BIOS flash. However this time I used a SOIC clip for in-system BIOS programming. That's the first time I try this on a laptop, and I had some difficulties to get the BIOS to be read at first. Maybe I did something wrong there. (though I checked multiple times that I didn't reverse the pinout)

[caspian]

Re: Asus X450LC no power (no PM_SLP_S4#)

I have read a similar problem during in-system BIOS programming yesterday in a thread that you have read too:
www.badcaps.net/forum/showthread.php?t=66760

It seems in-system BIOS programming will damage the mainboard sometimes, even if the adapter is connected properly to the Bios chip. this is probably because of the fact that SIO and other components which are connected to the Bios chip, are not made in a way to accept in-system BIOS programming. this is just my guess and I am not sure.

[zoltor]

Re: Asus X450LC no power (no PM_SLP_S4#)

I have read a similar problem during in-system BIOS programming yesterday in a thread that you have read too:
www.badcaps.net/forum/showthread.php?t=66760

It seems in-system BIOS programming will damage the mainboard sometimes, even if the adapter is connected properly to the Bios chip. this is probably because of the fact that SIO and other components which are connected to the Bios chip, are not made in a way to accept in-system BIOS programming. this is just my guess and I am not sure.

I think modern SPI Ic's are designed for 1.8 volts, when you connect the programmer it can supply 3.3 volts to this line. This can damage the elements in this chain. I never use in-circuit programming and do not recommend it to you.