The paper clip test isn't the best test. It actually provides a false positive, in that you may be inclined to believe that the PSU is fine just because the fan spins. A PSU does two major things:
1. Converts the alternating current (AC) from the wall into direct current (DC), which all electric devices require to power up; and
2. Distributes DC power on demand from the connected components.
Use a digital multimeter to test the voltages of the P1 connector. Click on the link in my signature to navigate to the troubleshooting page, where you'll find the typical voltage range. You'll also find some helpful tips for troubleshooting.