Came home from work, computer is off - not the way i left it!
It will not turn on at all. I tried a couple of different power cords and outlets - no luck.
I made sure the power switch on the PSU is on, and the wire from the case power button is connected to the motherboard.
No case fans spinning, no PSU fan spinning, no HDD spinup, and the LEDs on the mobo are off.
I haven't installed any internal hardware.
The computer is approximately 9 months old, and the power supply is an ANTEC Truepower 850 watt.
There have been no issues with the computer at all until today.
Is this possibly a motherboard issue? (I'm guessing not because the PSU fans are not even running)
It does sound like a PSU issue particularly if the fans on your PSU aren't going at all. Absolutely nothing happens at all yeah? I always thought those Antec models were pretty reliable... may have just been a bit of bad luck though. However it should still be under warranty so I would try that route first before you shell out for a new one.
If you can get your hands on a pair of voltage testers it may be a good idea just to test the output on the 24pin connector from your PSU just be sure.
Try to borrow a known good PSU of similar capacity. If you cannot do that, try to borrow a DMM to measure the voltages. Yellow wires should be 12 volts. Red wires: +5 volts, orange wires: +3.3 volts, blue wire : -12 volts, violet wire: 5 volts always on. The gray wire is really important. It should go from 0 to +5 volts when you turn the PSU on with the case switch. CPU needs this signal to boot.
You can turn on the PSU by completely disconnecting the PSU and using a paperclip or jumper wire to short the green wire to one of the neighboring black wires.
This checks the PSU under no load conditions, so it is not completely reliable. But if it can not pass this, it is dead. Then repeat the checks with the PSU plugged into the computer to put a load on the PSU.