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In a question posted recently here on SU the answer came up saying to "Never open a power supply, it has no user servicable parts".

Mine has a cable barely touching the PSU fan (I recon) and I dislike this greatly. What actions should I take to dislodge this annoyance?

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I have repaired many PSU's I guess it depends on your skill level. – Moab Oct 10 '11 at 3:24
I have gutted a few PSU's in my time but they were all already dead/old. This one I want to keep haha – Kurru Oct 10 '11 at 3:29
up vote 6 down vote accepted

You can of course open the PSU, but you must observe some precautions. First (obviously), unplug the unit. Leave it unplugged for 15 minutes or so. In most PSUs there are bleeder resistors that will bleed down the stored voltages inside over time BUT THERE ARE NO GUARANTEES!!

When you open the unit, understand that there are two hazards:

  1. Stored high voltage (200V or so) on the "input" side of the unit.
  2. Stored high currents (tens of amps) on the "output" side of the unit.

The high voltage represents an electrocution hazard. The high current represents a burn hazard should something metal (such as your ring or watchband) touch the wrong terminals.

If you just need to move/secure a loose wire, you should be able to do that without touching any bare wires or terminals inside the box. If necessary use an insulating stick (eg, a tongue depressor or chopstick) to probe and move things around. Be wary of using something like a pencil (the lead is conductive) or a ball-point pen (which has a metal tip and often other metal parts). And, of course, screwdrivers are almost always metal and a hazard inside.

Be sure to close the unit back up before you apply power again. It's too easy to "jump ahead" and apply power with the unit open, then "remember something" and reach inside the live unit without thinking.

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+1 for a good summary. Also worth mentioning that this will void any warranty. – Linker3000 Oct 10 '11 at 12:23
The warranty on all my computers expired 5-10 years ago. – Daniel R Hicks Oct 10 '11 at 12:49
Opened the psu case to find no wires able to reach the fan so a little confused what the cause was. In anycase the noise has now stopped, so thanks for your help! – Kurru Oct 12 '11 at 4:33
It could be the fan itself making noise -- they tend to produce a "playing card in the spokes" sort of sound when the bearings are going out. I've replaced PSU fans several times, and it's a relatively easy job in most cases. – Daniel R Hicks Oct 12 '11 at 22:37

Buy a new one. Or RMA it. What you describe doesn't sound like it is safe to use, especially if the cable touching the fan is making a noise.

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No need to be so dramatic. Unless it's a crap no-name chinese PSU (which you shouldn't use anyway since they're more like fireworks than PSUs), there is no risk even if the fan is stuck, the overheating protection will turn off the unit before any damage can occur. – user256743 Dec 1 '14 at 5:11

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