kotel wrote on 2025-11-01, 21:40:

The testing CPU is a Duron 750mHz D750AUT1B. Don't have any plastic athlons I could use which work at the moment. The one that I […]
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The testing CPU is a Duron 750mHz D750AUT1B. Don't have any plastic athlons I could use which work at the moment. The one that I do have is dead, hangs the board at C0-- with IRDY and FRAME LEDs lit and the board goes into a reset cycle (tested CPU in another known good mainboard, same thing).
I remember this CPU not playing nicely with a A7V8X-VM since it would hang at garbadge POST codes, while a plastic athlon worked fine.

No replacement ICS93738 ICs on ali too, so no way I can replace it without getting another similar board in a scrap lot.

Nexxen, could you check the value of your resistor which is between the ATX20 and IDE connector? I can't 100% recall if it was a 0ohm and the boardview I use doesn't list the part values.

I have that cpu. We can compare the readings.
Will check today.

R454 = 0 ohm (o is the marking)
RP5 = R331 (331 ohms)
D4 is 75 kohms from upper side lead to both lower side leads, lower side leads are not connected between them.

shevalier wrote on 2025-10-28, 16:46:

https://www.alldatasheet.com/datasheet-pdf/vi … T/ICS93738.html
But I can't even imagine how to check this other than by replacing it.
Even with an oscilloscope set to the correct frequency.

I might be able to borrow an oscilloscope, so maybe that could be helpful for diagnosis of it. Unsure what settings to choose tho. (I know the basic operation and how not to destroy it)

On another thought, it could be the SIO somehow being more damaged than having broken power on logic and wrecking havoc on the fan side and potentially RAM. Think I'll desolder it and see if the mainboard stops auto-powering on as a last resort (there aren't any jumpers for auto-power on like on older boards).

As for nexxen's readings, they are similar to the ones I get.

kotel wrote on 2025-12-26, 18:04:

I might be able to borrow an oscilloscope, so maybe that could be helpful for diagnosis of it. Unsure what settings to choose th […]
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shevalier wrote on 2025-10-28, 16:46:

https://www.alldatasheet.com/datasheet-pdf/vi … T/ICS93738.html
But I can't even imagine how to check this other than by replacing it.
Even with an oscilloscope set to the correct frequency.

I might be able to borrow an oscilloscope, so maybe that could be helpful for diagnosis of it. Unsure what settings to choose tho. (I know the basic operation and how not to destroy it)

On another thought, it could be the SIO somehow being more damaged than having broken power on logic and wrecking havoc on the fan side and potentially RAM. Think I'll desolder it and see if the mainboard stops auto-powering on as a last resort (there aren't any jumpers for auto-power on like on older boards).

As for nexxen's readings, they are similar to the ones I get.

After holidays I'll have more time, if needed I can measure stuff again.

Unfortunately I just given up hopes on this and wrote it off as a lost cause.
Thanks to everybody for helping me.