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Why would a notebook not shut down completely?


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Gateway NV7921U, Win7 HP

 

After a shut down, an attached USB notebook light and cooler fan remain partially on, but not completely.  The light dims and the fan slows.  This is with the AC cord attached.  If I unplug the AC cord and go to battery, the cooler fan dies, but the light remains on, though even dimmer.

 

The notebook itself appears to shut down fully.

 

The only external power that remains applied, is to two USB EHDs via a powered 10 port USB hub,   Could there be enough power feeding back from those?

 

 

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Hadn't even thought of that until I started typing, so I decided to try it.

 

Sure enough with that USB cable unplugged, everything shuts down.  Not sure I'm wild about that kind of bleed through, but at least it's all on a UPS to protect from surges somewhat.

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Believe it or not, USB is designed in a manner similar to original Ethernet networks. (I.e. one large bus.)

Basically, all your USB devices are connected directly together unless you have a motherboard that specifically separates them. (Typically Desktop boards tend to separate the rear panels from the onboard additional headers.)

So yes, there can easily be enough power back-feeding.

http://electronics.stackexchange.com/questions/115452/are-usb-hubs-that-backfeed-power-upstream-bad

Thanks,

EBrown

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