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PC Power Supply Discussion Troubleshooting and discussion of computer power supplies

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Old 03-24-2012
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Default Fan still running after power is unplugged. For 15 minutes

I found this thread at OCN.

Quote:
I have the cooler master elite 430 case and it came with one blue led fan in front

It was originally attached to the motherboard and after shutdown, the LEDs are still on and the blade is running at minimum rpm. I even used my finger to stop the blade and it spun on. When I unplugged the fan from the motherboard, it immediately shut off.

Then I used a 3pin to molex connector and connected the fan directly to the power supply. The same thing happened. I switched off the power supply and unplugged it from the wall and the fan continued to spin for 15 min....and kept going before I got impatient and I unplugged the fan.
One responder wrote this:
Quote:
Most likely capacitors are holding a charge even when turned off, and its supplying power to fans, which don't draw much, causing that 15 minute run time.

Most capacitors have a bleeder resistor that should stop that, so your PSU may be faulty.
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Old 03-24-2012
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If it really is 15 minutes, those must be some monster hold-up caps... Even with a trickle drain, they shouldn't last for more than a couple of minutes. When untapped, though, big caps can hold quite a charge for hours.

What bugs me in this case, is how is it that only the fan was supplied with power, and not the rest of the components? What kind of motherboard passes current to the fans when in S5 state? Interesting.

As for the bleeder resistor, I've seen quite a few PSUs without one. They're just shitty, as opposed to faulty.
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Old 03-24-2012
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15 minutes seems unlikely.
Unreal even> cool down circuit misbehaving in both cases > ??
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Old 03-24-2012
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I think his PSU manufacturer invented perpetual motion without knowing it.
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Old 03-24-2012
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Don't worry about it. I've had review samples that spun their own fan for ages after power cord removal. It's not a sign of failure.
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Old 03-24-2012
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But why does the MoBo pass current to the fan(s), even though it's turned off? Was it, perhaps, in some state other than off (S5)? Maybe S4 or even S3..?

I'm puzzled.
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