While everyone is out of ideas I think I'm going to try simulating a debounced button with a microcontroller to see if it will help.

The only thing connected to power button on P2Bx so most likely also P3Bx are 3 resistors and one capacitor
one resistors pulls it to 5V
two resistors between button and 2 pins of Super I/O
capacitor to the ground - this is for debouncing

tldr - look for small ceramic smd capacitor

r00tb33r wrote on 2024-08-12, 10:50:

While everyone is out of ideas I think I'm going to try simulating a debounced button with a microcontroller to see if it will help.

I put this to the test with an Arduino. Arduino pulls the POWER_SW pin LOW for 4.5 seconds, the machine shuts off, but as soon as the pin goes HIGH (equivalent of button released, because of pull-up), the machine turns on again. This should not happen. There is a fault on this motherboard. (And I honestly didn't believe it was a debouncing problem, even though it looked like it.)

Also, I think it drains the CMOS backup coin cell battery too fast, I replaced it, but it loses settings even if I switch off the power supply even for minutes.

Ideas regarding what would cause these faults?

I removed the motherboard from the case and found a damaged SMD component.

I have difficulty reading the marking. It's 30-something? I think silkscreen corresponds with D13. Anybody got a schematic?

Soldering is not a problem, both iron and hot air. I may be able to correct this one, or replace it.

Can someone help me identify the component? I would like to identify it before I try soldering it because it might make reading it even more difficult.

In the meantime it seems I have fixed the broken component. Two pins were completely broken off, I used a grinding pen to expose more metal so I could solder to it. Then built up the pin connections with solder blobs to connect to the pads. Seems to have worked.

So soft power off with the button seems to work now.

Not sure about the CMOS backup battery yet. Do these boards charge them or is it a one way trip with these if it dies?

Just replace the coin cell?

The diode probably handles the 5V standby line, so the RTC has been running off the battery the entire time...

ux-3 wrote on 2024-08-22, 11:20:

Just replace the coin cell?

I don't have any fresh spares around. But I removed it and it measures 3.1V with no load, so I guess it's not quite bad yet, but not fresh either (Google-fu says they can be as high as 3.6V no load when fresh).

I guess I'll just have to test some more after I fixed that diode...

its a dual diode
OnP2B there is a diode for VBAT near AS99127 and it looks like this is what was ripped on your board.

>Two pins were completely broken off

How did it hold cmos before ?? the only connection to battery is thru that diode
Sounds like only one pad was ripped - between 3V and Chipset | SuperIO | AS99127 VBAT inputs. Its possible those chips keep VBAT consumption in extreme low power mode when turned OFF, but assume unlimited power on VBAT input when fully powered. This would explain battery draining quickly.

no, its definitely what jmarsh said:

jmarsh wrote on 2024-08-22, 11:24:

The diode probably handles the 5V standby line, so the RTC has been running off the battery the entire time...

diode links 3VSB to VBAT line

its weird this diode would break turning off tho
only p2b diagrams/ boardviews are available Re: Early revision ASUS P2B and Coppermine Pentium 3

r00tb33r wrote on 2024-08-22, 09:06:

I removed the motherboard from the case and found a damaged SMD component. […]
Show full quote

I removed the motherboard from the case and found a damaged SMD component.

The attachment IMG_20240822_050110.jpg is no longer available

I have difficulty reading the marking. It's 30-something? I think silkscreen corresponds with D13. Anybody got a schematic?

Soldering is not a problem, both iron and hot air. I may be able to correct this one, or replace it.

Can someone help me identify the component? I would like to identify it before I try soldering it because it might make reading it even more difficult.

looks to be 303. Might be wrong tho..

rasz_pl wrote on 2024-08-22, 11:55:

its a dual diode

Yeah, I figured that out by probing the pads, they're all connected to the circuit, so I knew it's a dual at that point. I suspect most SOT-23-3 dual diodes would have gotten the soft power off working, not sure about RTC backup though...

rasz_pl wrote on 2024-08-22, 11:55:

How did it hold cmos before ?? the only connection to battery is thru that diode
Sounds like only one pad was ripped - between 3V and Chipset | SuperIO | AS99127 VBAT inputs. Its possible those chips keep VBAT consumption in extreme low power mode when turned OFF, but assume unlimited power on VBAT input when fully powered. This would explain battery draining quickly.

It didn't. It would only keep settings while the power supply was on.

Two pins were completely broken, the pads on the board are fine though. Seems I fixed both problems though as it keeps CMOS settings now. Seems the replacement battery was still good.

rasz_pl wrote on 2024-08-22, 11:55:

its weird this diode would break turning off tho

Yeah, lucky me that it wasn't completely dead, I would have probably tossed it if it didn't power on at all (and I didn't spot broken components). This stuff is old and lived many lives before I got around to it. I actually saved it from going in the trash like way back in 2008. A repairman botched BIOS update on it and ended up buying a replacement for the customer... I flashed the BIOS chip and kept the board for future use when I will want to play with my ISA sound card collection. That came about more recently. It was stored in a pile of boards until then. So not sure at what point the diode got knocked off, possibly years ago.

rasz_pl wrote on 2024-08-22, 11:55:

only p2b diagrams/ boardviews are available Re: Early revision ASUS P2B and Coppermine Pentium 3

Thanks for the link. I haven't worked with this style of board views before, gonna be interesting.