Power feedback on powered usb hub

[vulgartrendkill]

Hi,

So, I've been reading up about usb hubs and them receiving power from both usb cable and the external power supply and I was wondering if snipping the red (5v + lane) on both sides pc and hub, would stop the power feedback problem?

For example, when I plug my hub into the usb port on my pc and then attached the external supply (without plugging it in) the psu lights up (receiving power). 

Would snipping the red wire on the usb enable communication but disable power?  Do I need to cut ground also or would this be ok?

Thanks 

[HellDiverUK]

Power feedback problem? 

[vulgartrendkill]

Where the usb power from the pc usb port being used somehow gets to the psu. It baffles me also.

[HellDiverUK]

Must be a really cheap hub if it doesn't have a diode in there somewhere to stop that happening.

[amigaman]

You can't use a diode, you'll need to have a circuit with controller and Mosfet, that's too expensive, hence most chinese hibs don't have this: they simply parallel power supply plus and pc plus.

and yes, cutting the red line would help. cutting the ground line not, that's not a good idea.
some hubs have a fuse in there, desoldering it would also help.

[vulgartrendkill]

Thanks Amigaman, that was my feeling just as I`m not that versed in messing with electronics I thought I would check!

[Photon939]

You can't use a diode, you'll need to have a circuit with controller and Mosfet, that's too expensive, hence most chinese hibs don't have this: they simply parallel power supply plus and pc plus.

and yes, cutting the red line would help. cutting the ground line not, that's not a good idea.
some hubs have a fuse in there, desoldering it would also help.

Diodes do work, although if you go that route you will want to use a schottky diode to minimize the voltage drop.

Just desoldering or cutting the red wire going from the host pc to the hub pcb is easier and will accomplish the same goal, it just won't let the hub work unpowered anymore.

[zombie112]

Cutting the red wire would work. I tried with a really cheap USB hub, but apparently the power supply was so weak that it came with, that it didn't have enough power to charge a phone reliably or power a USB Wireless Adapter. Yours may be different though.