PC won't power on if I leave a powered USB hub plugged in

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PC won't power on if I leave a powered USB hub plugged in

Postposted on Sat Mar 30, 2013 12:42 pm

I've run across a rather interesting issue with my system and I'm wondering what you guys make of it. I have a cheap no-frills Gigabyte 1155 motherboard, crappy no-name powered USB hub, and an old 500W PSU that survived an accident but keeps on chugging. If I plug in the hub's external power supply the system runs fine for a while, but after a few days it will no longer turn on. If I unplug the hub from its power adapter (but leave it connected to the PC), switch off the PSU, wait a few minutes, then switch on the PSU and power on it's back to normal. And it will continue to run fine until I plug in the hub's external power adapter for a few days.

Based on the times involved it's pretty obvious a capacitor is getting drained but I'm curious which component is misbehaving.
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Re: PC won't power on if I leave a powered USB hub plugged i

Postposted on Sat Mar 30, 2013 1:22 pm

My immediate reaction is to check your BIOS for the boot order. USB devices can sometimes interfere with priority. I'm not sure why there would be a delayed manifestation of the symptom though.
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Re: PC won't power on if I leave a powered USB hub plugged i

Postposted on Sat Mar 30, 2013 1:23 pm

Well, open up the case, inspect the capacitors on the motherboard, do the same with PSU (but be careful not to zap yourself), see if any of them are bulging/leaking...
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Re: PC won't power on if I leave a powered USB hub plugged i

Postposted on Sat Mar 30, 2013 1:29 pm

NovusBogus wrote:...cheap no-frills Gigabyte 1155 motherboard, crappy no-name powered USB hub, and an old 500W PSU that survived an accident but keeps on chugging. ...


Just sayin'.

But really, probably time to replace some stuff.
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Re: PC won't power on if I leave a powered USB hub plugged i

Postposted on Sat Mar 30, 2013 1:36 pm

I've occasionally seen strange behaviors like this before. Sounds like power from the hub is flowing back along the USB cable when the main system is powered off, and causing some problems with the motherboard and/or PSU.

Tough to say which component is ultimately at fault here, but I'd start by swapping out the USB hub for a name-brand one.

@JohnC - No idea why you think this is a defective capacitor issue, the symptoms don't fit at all.
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Re: PC won't power on if I leave a powered USB hub plugged i

Postposted on Sat Mar 30, 2013 2:53 pm

just brew it! wrote:@JohnC - No idea why you think this is a defective capacitor issue, the symptoms don't fit at all.

Well, it wasn't me who suspected them in first place... But it is still a possibility - I've seen just about all kinds of symptoms that were eventually traced to bad mobo caps. Of course in this case it may simply be a defective hub (such as defective capacitors in the hub itself).
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Re: PC won't power on if I leave a powered USB hub plugged i

Postposted on Sat Mar 30, 2013 6:02 pm

JohnC wrote:Well, it wasn't me who suspected them in first place...

Actually, it was.

All the OP said was that it seemed like some capacitor was getting drained when he unplugged the hub for a while, allowing the system to boot again. He said nothing about suspecting *defective* capacitors.
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Re: PC won't power on if I leave a powered USB hub plugged i

Postposted on Sat Mar 30, 2013 6:22 pm

I had the exact same problem, even replaced the power supply. Unplugged the usb hub just by sheer luck and no more problems.
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Re: PC won't power on if I leave a powered USB hub plugged i

Postposted on Sat Mar 30, 2013 8:17 pm

I got a nice bonus and a fat stack of cash from changing jobs so I am indeed looking at upgrading some/all of those parts in the near future. My suspicion is likewise on the hub though I would have thought a motherboard would keep its core components more isolated since making any assumptions about connected devices is terrible design practice.
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Re: PC won't power on if I leave a powered USB hub plugged i

Postposted on Sat Mar 30, 2013 8:20 pm

Lots of threads I visited on other forums all point to the powered hub. Like maybe the cheaply-made ones feed power back to the PC and it gets confused or something.
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Re: PC won't power on if I leave a powered USB hub plugged i

Postposted on Sat Mar 30, 2013 8:22 pm

NovusBogus wrote:I got a nice bonus and a fat stack of cash from changing jobs
I seriously thought this was going to be one of those "work from home" spam posts. (ㅇㅅㅇ;)
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Re: PC won't power on if I leave a powered USB hub plugged i

Postposted on Sat Mar 30, 2013 8:43 pm

NovusBogus wrote:My suspicion is likewise on the hub though I would have thought a motherboard would keep its core components more isolated since making any assumptions about connected devices is terrible design practice.

You would think so, but evidence says otherwise. I remember a system I built a few years ago where plugging in a powered hub would cause the rear case exhaust fan to spin slowly even when the system was powered off. WTF.
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Re: PC won't power on if I leave a powered USB hub plugged i

Postposted on Sat Mar 30, 2013 9:20 pm

just brew it! wrote:You would think so, but evidence says otherwise. I remember a system I built a few years ago where plugging in a powered hub would cause the rear case exhaust fan to spin slowly even when the system was powered off. WTF.

My old system did that too...it was an interesting "feature". :lol:
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