White Powder Around Back Of Motherboard

Hi @josephcour78263

A short time in an ultrasonic cleaner may be more beneficial as this would get rid of any corrosion in hard to get at places e.g. CPU socket.

The board is looking fairly clean so hopefully there's not too much water damage but given that it was in the trash, you don't know what's wrong with it.

I would gently clean it all over with Isopropyl Alcohol 99%+ but just make sure that you don't get the board too wet as the traces may lift off from the board. Also be gentle with the brush you don't want to remove any components from the board either.

The CPU has been removed (presumably not by you) so maybe the original was OK and that there were other problems with the board that the owner couldn't resolve.

Do you have a DMM (digital multimeter) and know how to use it?

If so, here's the schematic for the motherboard series i.e. MSI 7C95 that may help.

Once you're satisfied that the board is clean etc, go to p.62 in the schematic and view the ATX power connector connections on the board. Use the DMM to make sure that there's no short circuit i.e. 0.00 Ohms, when measuring between ground and all of the voltage rails shown that are connected there. Some may have a low resistance but it shouldn't be short circuit.

If all seems OK, connect the PSU but without the CPU installed and turn it on and check if the debug LED on the board indicates that the CPU is not detected. (You need the power button cable from the case inserted into the appropriate board socket to turn it on - see p.vii 7 of 357 of the user manual) Be alert for any smoke, components showing heat glow etc etc coming from the board so that you can quickly turn off the power to the PSU.

If all appears to be OK, try the CPU and see what happens.