Rebuild / Repair PSU for Dell 960 SFF? (Code 3)

Is there anyone that rebuilds Dell power supplies? We have about 220 small form factor Dell 960 desktops that were bought in about 2009. They are still good machines, bought with 4gb (2gbx2) with room to grow, and Core 2 processors, but we are starting to see the power supplies fail one after the other.

It's always the same thing, computer won't turn on, press the power button and Code 3 lights up on the front. Dell manuals suggest it's a motherboard failure but my testing has demonstrated it's really a power supply problem. Replacing the power supply with a new unit, always fixes it.

The problem is, it costs around $120 or more for a new OEM Dell power supply, and this gets quite expensive to be replacing 10-20 power supplies per year, always for the same exact situation.

At this point I assume all Dell small-form-factor power supplies share a common defect. Some part just doesn't hold up to the heat of these compact low-fan-speed machines, and becomes erratic. It wouldn't surprise me at all to discover it's a failing capacitor that's gone out of tolerance due to the heat.

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I've started holding onto the failed power supplies. If I can find what the exact component failure reason is, I can start repairing them myself for the individual component cost of $1-2 each, rather than constantly having to buy whole new $120+ power supply units, which are becoming increasingly uncommon as the system ages.

Has anyone else out there tackled this problem? Any leads on what exactly the failed component is in the PSU?

(I'm familiar with the hazards of testing and repairing PSU's, such as big capacitors can hold a potentially hazardous charge after the device is unplugged, etc.)