Hi guys ! When the computer mainboard can’t be powered on, you have to check the power supply again, check if the clear CMOS jump is correct? Replace 32.768 KHz quartz. Check to see if the source circuit is in any form, in the South chip, in the ISO and if there is an inverting amplifier light…. You can refer to the article: The steps to fix the mainboard can’t hit the source that I mentioned. However, many times we have done all those steps but still can’t activate the source
I would like to share with you my experience of fixing Asus mainboard that cannot be activated, which I have done successfully. When we have done simple steps such as replacing the quartz, checking the CMOS jump and measuring, we know the source circuit goes to the SIO chip. I made the following measurements:
Check the RTC circuit: There is an OK voltage source.
3.3v power supply for the Southbridge chip: Ok, can be measured at the A14 pin of the PCI slot or measured near a few small children next to the South chip.
The power cord (green) on the 20 or 24 PIN power jack connects to pin 72 of the IO chip: Good.
Pin 68 of IO when the source is not activated has 3.3v. When conducting the source, the pin 68 loses voltage >> OK. Some Aus Mainboards do not design power jacks directly to the IO chip, but through the children, so do not measure directly.
Pin 61 SIO (source before 3VSB) has 3.3V: Sufficient power.
Pin 75 SIO (RSMRST) has 3.3V : Good
Pin 73 SIO (SLP_S3) has only 0.8V : Undervoltage. Pin 73 of the IO must have a standard voltage of 3.3v. This is the cause of the mainboard not being able to power. Pin 73 receives the SLP_S3 command from the male chip, so the error may be caused by the male chip or IO.
If we proceed to eliminate it by trying to replace the SIO chip or the South chip, it is too time consuming and expensive. To be fast and economical, we just need to connect pin 61 ( 3VSB ) to pin 73 to fake the command. And as a result, the mainboard was powered on and booted up normally.
This way I have successfully done on Asus P5G41T – MLX mainboard using Winbond W83627DHG-A IO chip, Asus P5GC-MX/1333 mainboard using W83627EHG IO. And some Asrock mainboards use IO chips as above. Wishing you success
