Need help in repairing a dead motherboard

[stealthjoe]

Hello,

I have a Pentium 3 motherboard (iWill VA133plus) and yesterday I took it out from storage to test a processor. However, the board does not power on. Normally, the standby LED is illuminated when the PSU is connected. In my case, the LED is still off despite connected to the PSU in ON state. So due to this, I am unable to boot/post the motherboard. The voltages across the MOSFETs are also zero as the motherboard is not receiving any power.

Attached below are the images of the board specifically around the ATX connector. Could someone please share their experience with such an issue and the troubleshooting steps? Thanks.

 

[sagor1]

Did you check F3? It is a fuse that probably feeds some of the power to Q15 and Q14.
Remember that the PSU needs a "start" signal (usually the green wire to ground) to in effect turn on.
Try a different power supply if possible...

 

[rjenkinsgb]

If there is no standby power, it's likely a PSU fault.

With the PSU not connected to the motherboard but powered on, do you get 5V between the purple 5V standby wire and one of the black ones?

 

[ahsrabrifat]

Hello,

I have a Pentium 3 motherboard (iWill VA133plus) and yesterday I took it out from storage to test a processor. However, the board does not power on. Normally, the standby LED is illuminated when the PSU is connected. In my case, the LED is still off despite connected to the PSU in ON state. So due to this, I am unable to boot/post the motherboard. The voltages across the MOSFETs are also zero as the motherboard is not receiving any power.

Attached below are the images of the board specifically around the ATX connector. Could someone please share their experience with such an issue and the troubleshooting steps? Thanks.

Use a multimeter to test the purple wire (pin 9) of the ATX connector for +5V relative to any ground pin (black wire).
This voltage must always be present when the PSU is plugged in and turned on. If there’s no +5V on pin 9, the power supply may be faulty or not turning on.
.Sometimes solder joints on the bottom of the board become oxidized, cracked, or dry. Check the bottom of the ATX connector under magnification. Reflow any questionable joints.
Unplug the board and visually inspect for burn marks or damaged components near the ATX connector.
Leaking or bulging capacitors, especially the ones around the power input and CPU VRM area.
Corrosion or insect residue if stored in a humid or dirty environment.
With the board disconnected from power, use a multimeter in continuity mode measure across +5VSB to GND at the ATX socket. If it beeps (short) — there's likely a shorted capacitor or failed IC.
If you are interested in making any type of computer motherboard by yourself, you can see this:

Omega Home Computer Motherboard (MSX2 Compatible) - Share Project - PCBWay

ORIGINAL GITHUB: https://github.com/skiselev/omega

www.pcbway.com