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View Full Version : Back-feed from USB Hub??



Billy T
17-05-2009, 04:49 PM
Hi Team

Ever seen anything like this before?

I just bought a new digitech 7-Port USB-2 hub from Jaycar and it comes with its own power supply.

If the power is left on to the hub, when I shut down my computer the front cooling fans keep running and the CD drive light comes on. More importantly however, it won't start up again unless I unplug the power from the Hub, so obviously there is a 5-volt back-feed into the PC.

I am using three ports on the computer and five of the ports on the hub, the other two being top mounts for USB sticks etc. Nothing is actually being powered by the Hub, it has three printers, camera and mouse attached so I assume that I can safely dispense with the separate power supply and get rid of the problem that way?

Cheers

Billy 8-{) :confused:

pctek
17-05-2009, 05:50 PM
Oh er. I'd dump the entire thing and buy a Logitech.

Billy T
17-05-2009, 06:12 PM
Mmm...........I was thinking that, but then this one replaces a DSE 7-port hub that literally fell apart when you pushed a plug in one side. I had to use cable ties to hold it together. Despite that inauspicious start, it worked well until the power supply went up in a cloud of heifer-dust so that went back for a refund.

I guess I'll give this one a fair go if it will work without its power supply, and I can't see why it wouldn't. Jaycar will refund if it doesn't work out.

My main reason for posting was to see if anybody had ever experienced back-feed from a powered hub into the computer. Maybe my computer is gay. :horrified

Cheers

Billy 8-{)

Billy T
17-05-2009, 11:28 PM
Well, it seems to be running quite happily without the power supply and everything boots up OK so I've now got yet another spare 5V/2A plug pack to play with.

I swear these plug-packs breed, I've got a decent sized box full of the things stashed in my garage now. Apparently they call them wall-warts in the UK and I can understand why, they multiply like viruses too.

Cheers

Billy 8-{)

somebody
17-05-2009, 11:37 PM
Well, it seems to be running quite happily without the power supply and everything boots up OK so I've now got yet another spare 5V/2A plug pack to play with.

I swear these plug-packs breed, I've got a decent sized box full of the things stashed in my garage now. Apparently they call them wall-warts in the UK and I can understand why, they multiply like viruses too.

Cheers

Billy 8-{)

I wonder whether the manufacturer was trying to cut costs by eliminating a diode on the +5v line (i.e. the power should go from PC->Hub, but not the other way around)? Since you've got an electronics background, maybe you could try soldering one in and see what happens.

gary67
18-05-2009, 07:43 AM
Well, it seems to be running quite happily without the power supply and everything boots up OK so I've now got yet another spare 5V/2A plug pack to play with.

I swear these plug-packs breed, I've got a decent sized box full of the things stashed in my garage now. Apparently they call them wall-warts in the UK and I can understand why, they multiply like viruses too.

Cheers

Billy 8-{)

Only ever heard Yanks and Canadians call them that not the English