Case fan spins when I plug in psu?

  • Thread starter Thread starter mrbog
  • Start date Start date
M

mrbog

When I plug in the psu, the case fan spins for a half second, as if
power just went through it.

Is that supposed to happen?

I don't mean when I turn on the machine, I mean just plugging the
power cord into the PSU.
 
ATX/BTX have constant power at the moment you plug into the source.
Provided the source is live and the PSU's switch on the back is
flipped on. (if applicable, as some don't have the switch) The
momentary spin may be a 'feature' of the particular PSU.
 
mrbog said:
When I plug in the psu, the case fan spins for a half second, as if
power just went through it.

Is that supposed to happen?

I don't mean when I turn on the machine, I mean just plugging the
power cord into the PSU.
Click to expand...

When you plug AC into your PSU, the internal Vcc voltage that controls
whether your PSU is ON or OFF rises from 0 volts to its operating voltage
(be it 5v, 12v, 15v, etc.) Until it does so, the PSU ON/OFF logic is not
able to tell the PSU whether it should be ON or OFF. Some PSUs clamp the
output OFF during this very brief period. Others (such as yours) do not.

Nothing to worry about, really.
 
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