Question Fixing old Z97-C, Rear i/o not working,

[BolivianGamer]

Hi!,
I have an ASUS Z97-C Board working with an i5 4690k processor, they have been paired for a long time
a few years ago by mistake my fan rails shorted, and almost killed everything, fortunately, a computer technician managed to get it booting again.
however, the motherboards rear USB ports do not work, nor do front USB 3.0 and 2/3 front usb.
it is now working using a PCI-USB extension card

the rear USB ports get voltage, but no data, nor recognition from the OS.

i tried to get the schematics/board-views for this motherboard, but i only managed to get board-views for a similar model. this indicated that all rear i/o is connected to the south-bridge.
i hope that the fact that ethernet works correctly is a sign that the silicon is working correctly.

i wish to understand a bit better what could be the source of this problem, and if i would be able to fix it.
I'm not afraid of a bit of smd soldering if needed

Thank you

 

[punkncat]

This cutsheet:

4th-gen-core-family-mobile-product-brief-v2.indd (intel.com)

indicates that the USB support is integrated into the CPU/Chipset. It might be worthwhile to see if you can source a really cheap 4th gen processor to test in place to see if the issue persists.

 

[BolivianGamer]

This cutsheet:

4th-gen-core-family-mobile-product-brief-v2.indd (intel.com)

indicates that the USB support is integrated into the CPU/Chipset. It might be worthwhile to see if you can source a really cheap 4th gen processor to test in place to see if the issue persists.

Thanks!
i ve been looking for 4th gen cpus, in the mean time i managed to solve the problem, kinda

i began guessing that the chipset was not damaged, because that would stop almost everything from working, (SATA, audio, some USBs) and also, the usb controller were recognized by the OS. That focused me onto the port and the surrounding components,

This is the boardview i managed to get (there is no Z97-C boardview, but the z97-e has the similar layout, and same value components in the io and audio traces)

i checked the way the LAN port is connected and, how the USB ports are connected. basically drawing a little schematic of how its working,
i observed that LAN and USB shared a component (UD102, L1D1, L2D2)

because the LAN port is working, i compared the values of diode voltage drop in pins 5 and 2

Lo and behold, non working ports had, a voltage drop of 0.1V, to 0.056V and working ports had ~0.3V

this diode array is connected in parallel to the data connections to the chipset, and is used to protect against esd spikes. desoldering it would not cut the data lines

I desoldered them and now they are working!

I have to source replacements, but in the mean time its working correctly



Now i got to make the audio work

I been stuck there because the OS recognizes the chip, but says there is no device connected to the jacks, however i have confirmed that the mechanical jacks and traces are alright.

Any ideas on how i could diagnose that problem, or where i could ask about it?