Do you have a fan plugged to the CPU fan header? There were a few boards wouldn't start without one.

When the system is powered on can you turn it off by holding the power switch down?

Oh btw, another quirk, some of these Slot era Asus, if the power is set to soft on or something in the confusing power menu, they don't start until you press keyboard power or wake button or hammer the space bar.

Thank's for the tipps.

Unfortunately the system is not power down if i hold the power switch (i removed the paperclip after booting).

Wake on keyboard is disabled in BIOS and the jumper on the mainboard for the feature is not soldered. It has revision 2.04.

Fan is plugged in the CPU fan header and spins.

very strange mainboard.

EDIT:
I tried to enable wake on keyboard (space bar) in BIOS which also did not work. Maybe the board is damaged.

The backside of the connector looks very strange.

Corrosion? but there is no barrel battery etc. What happened to this mainboard!?

Maybe you have a problem on the 5V SB rail of the board .

'Wake on keyboard is disabled in BIOS and the jumper on the mainboard for the feature is not soldered. It has revision 2.04.'

Check if you have 5 volts on both ends of the jumper .

If you haven't done so already, try a new CMOS battery, or if you have a meter, verify that the battery has the correct voltage. There are motherboards that won't POST without a CMOS battery.

Repo Man11 wrote on 2023-03-03, 17:06:

If you haven't done so already, try a new CMOS battery, or if you have a meter, verify that the battery has the correct voltage. There are motherboards that won't POST without a CMOS battery.

I thought about mentioning that, but was guessing that it would show up on the POST screen above... but yeah ASUS are really, really, highly, extremely, ridiculously picky about having good CMOS batteries in.... and by good, not even "but it holds settings and time on my other machine even though it was only new last year" .... hell, give that machine batteries when the ASUS is done with them, but literally almost factory fresh... though they don't seem to "eat" them per se, it's weird like they need high volts to initialise a new setup or something.

From my experience with Asus boards , yes , some have a problem POSTING with a bad CMOS battery but not a no PSU on/no fan spin .

CrazyChris wrote on 2023-03-03, 16:29:

The backside of the connector looks very strange.

Corrosion? but there is no barrel battery etc. What happened to this mainboard!?

Hey bro, nice board! That definitely looks like corrosion. I have seen that kind of damage on older x86 boards. It could have been in contact with corroded batteries from a different source.

My advice is to gently scrape/sand those compromised contacts, use vinegar on them to dissolve the residue and then re-solder or add fresh solder to the joints to end up with nice looking joints.

Then measure the continuity between the PSU connector pins on the board and some traces to see if there's a broken trace somewhere.

And probably this will solve your problem... scratch the surface of the pins where the power switch is on the front panel. They could be corroded too, or dirty. To be sure, check the continuity between one of them with ground and the other with the correct pin on the PSU connector.

Is there a generic circuit diagram how the power button pins are working with an ATX power supply?

bogdanpaulb wrote on 2023-03-03, 16:31:

Maybe you have a problem on the 5V SB rail of the board .

'Wake on keyboard is disabled in BIOS and the jumper on the mainboard for the feature is not soldered. It has revision 2.04.'

Check if you have 5 volts on both ends of the jumper .

Such a diagram would be useless because there are many implementations/variables involved , you need one for you motherboard . The basic way that the power on circuitry works on a ATX board is : you have 5V SB (standby) from the atx power supply which is a different 5v rail ( it basically provides 5v continuously to the board/system even when it is shut down ) then the 'usual' 5v one . That voltage usually goes in to the chipset trough a voltage regulator, depending of the chipset ( south bridge in your case ) were it feeds the system power management block ( to which the pw on connector leads to ) , also that 5v SB is feeding the super i/o chip/chips so you can be able to turn your system on via kb or mouse . When you press the power button , the chipset 'senses' that and 'pulls the 'power on' pin of the power supply to ground' , which turns on the main rails of the PSU , if 'power good' checks out , keeps the system powered on , which makes the system start . That's why i asked you in the previous post if you can confirm that you have 5v SB present on your board . Without it , none of the above can happen .

If 5v SB is present on the board , then the next step is to check if 'power on' from the atx connector on the board leads to something , because i saw some corrosion and the trace might be damaged ( cant tell that from the pic you posted ).

bogdanpaulb wrote on 2023-03-09, 14:02:

bogdanpaulb wrote on 2023-03-03, 16:31:

Maybe you have a problem on the 5V SB rail of the board .

'Wake on keyboard is disabled in BIOS and the jumper on the mainboard for the feature is not soldered. It has revision 2.04.'

Check if you have 5 volts on both ends of the jumper .

Such a diagram would be useless because there are many implementations/variables involved , you need one for your motherboard . The basic way that the power on circuitry works on a ATX board is : you have 5V SB (standby) from the atx power supply which is a different 5v rail ( it basically provides 5v continuously to the board/system even when it is shut down ) then the 'usual' 5v one . That voltage usually goes in to the chipset trough a voltage regulator, depending of the chipset ( south bridge in your case ) were it feeds the system power management block ( to which the pw on connector leads to ) , also that 5v SB is feeding the super i/o chip/chips so you can be able to turn your system on via kb or mouse . When you press the power button , the chipset 'senses' that and 'pulls the 'power on' pin of the power supply to ground' , which turns on the main rails of the PSU , if 'power good' checks out , keeps the system powered on , which makes the system start . That's why i asked you in the previous post if you can confirm that you have 5v SB present on your board . Without it , none of the above can happen .

If 5v SB is present on the board , then the next step is to check if 'power on' from the atx connector on the board leads to something , because i saw some corrosion and the trace might be damaged ( cant tell that from the pic you posted ).

example diagram Re: Problem with ATX Soft Power Switch (Possible Fault on Motherboard) but for much older motherbaord

do you have a multimeter? PowerOn connector should have around 5V on one of the pins (pullup), then it goes thru few resistors all the way under PCI slots to the Winbond W83977TF chip. I dont know the exact pin number for P2L, on P2B its pin 72.

Winbond W83977TF will not start if it doesnt have good 5V power from 5Vsb, and will refuse to start if it cant detect PowerGood signal and in general few other conditions it likes like aforementioned cpu fan