Do not have an Intel DH55TC board so can not check the part.
Assuming everything works as it should that part would be connected to 5VSB if it had voltage and you grounded it direct with the shield (5VSB would be the only volts present if ATX PSU was off).
Should not effect the PCIE AFAIK and since the board boots it did not effect the power on stuff. Sorry is all I have at a quick guess....

Well I plugged in my PCIe x16 video card and PCI sound card back in and they seem to work without issues. So maybe this goes to the onboard sound that I already had disabled in CMOS since I always had an Audigy installed in the PCI slot . The onboard LAN seems fine as well, but if it was standby voltage could it be for WoL ? Just trying to figure out what exactly I broke

There's another 22A17 which is not burnt in your pic, I guess it's a p-channel mosfet from those thick traces.

What would a p Channel mosfet purpose be in this section more than likely? If it is not stressing some other components on the board or the other 22a17 then i guess i can leave it as is, but i probably won't be able to stop thinking about it. So is 22a17 what i need to look for as a replacement?

This is dual 5v rail for the audio chip, 5v standby goes through this mosfet then a diode then it looks like to the input of the 5v regulator (78l05) and when pc is on, the input of 5v regulator should get power from 12v rail.

Does this look like a suitable replacement?

https://www.mouser.com/ProductDetail/Vishay-S … 13oxTStOQ%3D%3D

Yeah it should work fine, if you have a multimeter, measure the source pad of the mosfet when pc is off to confirm it's getting 5v.

Karbist wrote on 2024-05-17, 15:20:

Yeah it should work fine, if you have a multimeter, measure the source pad of the mosfet when pc is off to confirm it's getting 5v.

20240514_202603.jpg

Yes just confirmed there is 5 volts present on the pad when the machine is not on. I have a few motherboards laying around that are donor boards, gonna go look and see if I can find that component without having to put in an order to Mouser.

Well the only thing I can find on my parts boards seems to be N type Mosfets and not P type from google searching the few letters and numbers on these chips. Guess I may have to purchase a new one next time I put in an order for new components.

For kicks I reenabled the onboard audio and to my surprise it finds the hardware and it plays windows sounds normally. Fired up a game of Max Payne 2 and everything sounds normal there as well. I did measure the voltage on the pads where the component went while it was on and I have voltage on all 3 pads. The top single pad has 5.02v the bottom right has 5.07v and the left bottom pad shows 6.04v

Here is a few shots from my donor boards with the SOT-23 looking candidates that seem to be wrong for this application.