Troubleshooting ATX Power Supply

[GAVolunteer]

Have eMachines T2862. System will not power up. LED on Motherboard lights up. Fans do not run. HDD does not powerup.

Checked ATX power supply. ATX-250-12E Rev:P7.

Red and Yellow are under voltage stds.
Orange shows 0 volts

Actual Voltage as follows:

On P2, P3, P5, P7 Red = 2.8v & Yellow = 7.8v (vs 5v and 12v)

On P8 Y = 7.8v vs. 12v

On 20 pin Motherboard connector:
Pin Actual Should Be
1. Orange +0.0 +3.3
2. Orange +0.0 +3.3
3. Black
4. Red +2.8 +5.0
5. Black
6. Red +2.8 +5.0
7. Black
8. Gray +0.0 ??
9. Purple +5.0 +5.0 Standby
10. Yellow +7.7 +12.0
11. Or./Brown +0.0 +3.3
12. Blue +2.6 ??
13. Black
14. Green +2.3 ??
15. Black
16. Black
17. Black
18. White +0.0 +5.0
19. Red +2.8 +5.0
20. Red +2.8 +5.0

Questions:
1. What do these numbers indicate as to the type of problem that exists with the power supply?
2. Can the power supply be repaired (by me) or should I just replace it?
3. Any other observations or troubleshooting ideas?

Thanks.

[racraft]

Do not attempt to repair a power supply. You won't be able to do so unless you have a schematic and can understand it and have the proper diagnostic and testing tools.

Besides, with the price of power supplies, it's not worth the time.

Those numbers may or may not mean anything. Without knowing how you tested and the specifics of the power supply ANY numbers are meaningless.

All of your symptoms point to the power supply.

[jmnew51]

The only sure fire way to test any power supply voltage is to do it with a load on it. The voltages you posted do seem to be off, but there's no way of knowing for sure if that's what your problem is.

Yes new PSU are cheap, not worth fixing. Go online $30 for 300 watt.

[ctmal]

The orange light being on can be caused by a couple of issues. First thing to try is to pull the memory, unplug the power from the drives, pci cards, etc. This is just to test if there is a short in any of those. If the power light is green, plug each back in 1 by 1. When won't turn on again, you've found your problem.
If that doesn't resolve the problem, if you have another power supply(maybe from another computer), plug that in. If that resolves the problem, buy a new power supply and put it in. If not, then the issue is most likely the motherboard or the cpu. After that, it would depend on the age of the computer on whether you would want to go any further.