USB3.0 self-powered hubs (with AC adapter) - do these USUALLY "back-feed" the PC's +5V line?

[VirtualLarry]

Or is this a design defect with the USB hub? Or my mobo's USB ports? (Blown diode / protector? Non-existent protector?)

What happened:

I built a PC for a friend a few days ago. I used a two-year-old ASRock AB350M Pro4 that I seemingly revived from "dead". It was working bread-boarded on a box, then I got it installed in a Rosewill Stryker M chassis, with a Rosewill Glacier 600W 80Plus Bronze PSU, and an RX 560 2GB.

Anyways, I got it all working, then swapped in the RX 570 that was the "real" video card that was supposed to end up in the new PC. (It was in the "old" PC.)

I powered down the new PC, switched OFF the PSU in the back, and then unscrewed/unplugged the RX 560 2GB, and then plugged in the RX 570 4GB (Asus ROG STRIX). Well, after I plugged it into the PCI-E slot, the RED LED lit up near the 6-pin PCI-E.

I was like WTF??? There's Power??? I SWITCHED OFF THE PSU!

Then I realized, I had left this cheap Chinese-made un-branded USB3.0 7-port hub with +5V PSU, plugged into a USB3.0 port.

It was BACK-FEEDING!

I unplugged the USB hub, I put in the RX 570 4GB card, then, when I switched on the PSU in back, it powered-on directly. BAAAAD SIGN.

I powered it off, using the soft-off ATX power switch, then powered it back on. From then on, it didn't want to reboot, even going into BIOS and "Save and Exit Setup", wouldn't reboot.

So, basically this cheap Chinese 7-port USB3.0 powered hub that's all over ebay (I bought from US seller) is DANGEROUS to PCs.

But, my next questions, shouldn't the motherboard have some sort of diode or protector on the USB3.0 port, to prevent back-feeding input from USB3.0 hubs and whatnot, from powering the PC off of it?

Edit: I swapped the Rosewill Glacier 600W 80Plus Bronze PSU for a Rosewill Valens 600W 80Plus Gold, still borked. So I need a new board for the rig. (I've got a few, waiting for my friend to get back to me about it.)

 

[mxnerd]

Don't think the USB hub is back-feeding. There is always some electricity left in the capacitors on the motherboard even if you power off/unplug the PSU.

The reason when you unplug the hub and the motherboard can boot immediately is because the motherboard doesn't try to boot from USB ports once you unplug the hub.

Nowadays motherboard BIOS setup is so confusing because every vendors design the BIOS differently, and it differs greatly between vendors, especially regarding the booting priority.

 

[VirtualLarry]

Don't think the USB hub is back-feeding. There is always some electricity left in the capacitors on the motherboard even if you power off/unplug the PSU.

No, it most definitely was. The *instant* I unplugged it, the red light on the GPU went off.

 

[mxnerd]

OK. So which 7-port USB 3.0 hub did you buy so I can avoid it?

 

[VirtualLarry]

https://www.ebay.com/itm/7-Port-Alu...-Power-Adapter-For-PC-Laptop-Mac/192686782570

It was from another vendor, but it was just like this one. It appears to work fine without the AC adapter plugged in, so I guess I'll use them that way.

Is it the fault of the USB hub, or the USB port on the PC though, that it is back-feeding? Is it supposed to have a diode or power-controller, on the hub, or on the PC's USB port, or both?

 

[mxnerd]

Is it the fault of the USB hub, or the USB port on the PC though, that it is back-feeding? Is it supposed to have a diode or power-controller, on the hub, or on the PC's USB port, or both?

No idea. But found the following discussions.

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

 

[VirtualLarry]

Thanks for the web detective work! Looks like... that's not a good thing to happen, and some people have had PCs and laptops damaged by such a thing.

the german Computer Magazin c't had not long ago (issue nr. 18/2014) an very interesting article about this theme - if you understand german language it's worth reading it: "Strom von hinten/USB-Hubs können PCs und Notebooks beschädigen" ("Current from behind/USB-Hubs can damage PCs and Notebooks"). For example they say that the old version of a Belkin F5U404cw USB-Hub was working correctly, but the new one (!) wasn't - little strange?! – user52564 Sep 4 '14 at 12:00

 

[mxnerd]

There are a lot of interesting USB power meter testers on Amazon.

https://www.amazon.com/s?k=USB+POWER+METER&i=tools&ref=nb_sb_noss_2

RUIDENG UM24C USB 2.0 reviewed on Youtube.

Improved UM25C

 

[mindless1]

The external hub is improperly designed, should not back feed to the computer. IIRC this was part of the USB2 spec if not USB1 also, and certainly would have carried on to USB3. The hub IC should sense and switch the port power while isolating it from the host.

The computer itself is not expected to have (diode) backfeed protection, nor would even a resettable polyfuse hold up if this happened every time the system is turned off, unless the hub's PSU was pretty weak but then why bother with one?

If you want to always use the hub with its own PSU, you might be able to just sever the power + line at the hub's port between it and the [computer] host, or get a 4 pin molex to DC barrel adapter that fits the hub's external power input socket to power the hub from the computer PSU's 5V rail, though if it is a charging hub and needs a bit over 5.0V for best results.... you then won't get best charging results.

 

[Torn Mind]

Anker is the only way to go if you want peace of mind with third party stuff that is coming out of China. It's like the equivalent of vintage Craftsman for tech addons, peripherals, and other small items.

(I don't own any Anker products)

 

[quartzz1]

just out of interest, I bought something like this

https://www.ebay.co.uk/itm/7-Port-U...Adapter-High-Speen-For-Laptop-PC/283429731360

the supplied adapter cord wouldn't reach from the floor to the desk, so I used a generic multi-voltage adapter, which after the event, I realised could only supply 300mA. plugging a 2.5" HDD into it (which takes up to 800mA) shut the laptop down. had to remove battery+mains to power back up. a commenter on here suggested a hard drive that was receiving half the mA it should be, was sending insufficient/corrupt data signals to the laptop, which made windows (7 64-bit) shut down. I replaced it with an Atollo hub...which.....has been mostly ok so far

 

[Seba]

https://www.ebay.com/itm/7-Port-Alu...-Power-Adapter-For-PC-Laptop-Mac/192686782570

It was from another vendor, but it was just like this one. It appears to work fine without the AC adapter plugged in, so I guess I'll use them that way.

Is it the fault of the USB hub, or the USB port on the PC though, that it is back-feeding? Is it supposed to have a diode or power-controller, on the hub, or on the PC's USB port, or both?

I would not even consider to use this type of a device as an USB hub. Only as a charging station for phones, tablets, etc. And not because it is powered.

 

[mindless1]

^ Something strange is going on, since it's link-titled as a 7 port aluminum hub and I remember it linking to a different product that was a hub, but the link now goes to a different product that's a 3 USB port charger (only) with no hub functionality at all.