[ 1. The PSU fan is not turning.
  2. The +/- 12 volt lines on the motherboard are not on their own the cause of the PSU fan not running (but could be a second problem - multiple shorted caps).
  3. There is no adequate load to test the power supply independently (to see if the PSU fan turns). ]



What Now?

We will now make some resistance measurements.
You will need a digital multimeter, and the knowledge of how to use it to make resistance measurements.

1. Turn off the power supply.

2. Disconnect both P8 and P9 from the motherboard.

p8_p9_removed.jpg


3. On the motherboard, measure the resistance between the ground line and the +5 volt line.

measure_plus_5.jpg
On the many good 5150/5160 motherboards that I have, this measurement ranges in value from about 200 ohms up to about 1300 ohms.

If your motherboard measures zero or a few ohms, then there is definitely a short circuit on the +5 volt line.
In either case, click HERE


4. On the motherboard, measure the resistance between the ground line and the -5 volt line.

measure_minus_5.jpg
On the many good 5150/5160 motherboards that I have, this measurement is so high that it it is beyond the capability of my multimeter. Initially, you may see a reading of some sort that slowly rises (as capacitors charge) but in the end, expect to see no reading.

If your motherboard measures zero or a few ohms, then there is definitely a short circuit on the -5 volt line.
In either case, click HERE


5. On the motherboard, measure the resistance between the ground line and the +12 volt line.

measure_plus_12.jpg
On the many good 5150/5160 motherboards that I have, this measurement is so high that it it is beyond the capability of my multimeter. Initially, you may see a reading of some sort that slowly rises (as capacitors charge) but in the end, expect to see no reading.

If your motherboard measures zero or a few ohms, then there is definitely a short circuit on the +12 volt line.
In either case, click HERE


6. On the motherboard, measure the resistance between the ground line and the -12 volt line.

measure_minus_12.jpg
On the many good 5150/5160 motherboards that I have, this measurement is so high that it it is beyond the capability of my multimeter. Initially, you may see a reading of some sort that slowly rises (as capacitors charge) but in the end, expect to see no reading.

If your motherboard measures zero or a few ohms, then there is definitely a short circuit on the -12 volt line.
In either case, click HERE



So you did not measure any shorts (or partial shorts) on the motherboard's power lines.

CONCLUSION:

Because:
1. there are no motherboard shorts, and
2. the power supply fan is not turning,
the logical deduction is that the power supply is faulty.