USB hub stopped working


Elrich

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A USB hub I was using (powered, four slots) stopped working a few days ago. It was ten years old, so I thought it just died -- if I plugged one hard drive directly into the Mac, it worked, so I figured it wasn't the USB slot, it was the hub. SoI got a new one (powered, seven slots). It worked for a couple days, and then this morning, the same thing is happening. The USB hub acts like it's not getting power, even though it's plugged in and the power strip is on. Other things plugged into the power strip are working. I can't understand where the problem is occurring. It's apparently not the hub itself, since two of them have behaved in the same way. Not the power strip. Not the Mac's USB slot. What's going on?
 
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Cory Cooper

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Hello,

-What brands/models are the USB hubs?
-What brand/model is the external hard drive? Is it bus-powered or does it have an AC adapter?
-How many devices are you connecting to the hub(s)?

My guess is you are drawing too much USB power, even though the hub is powered.

C
 

Elrich

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But the old one (made by Belkin) served well for a decade, most of that time with two or three external hard drives plugged into it, and something in the fourth slot filled as well.
The new one is an Elecom. It worked fine for a couple of days, and suddenly it stopped working.

The three external drives are a Seagate, a G Tech, and a Toshiba.

I found this page
and tried resetting SMC (the light didn't blink) and NVRAM, but neither worked.
 

Cory Cooper

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OK, thanks.

-Which exact model is the Mac? It depends on the model for how you would perform the SMC reset.
-Are the three external drives portable - i.e. without AC adapters, just USB cables?

C
 

Elrich

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It's a Macbook Pro 13" that I bought in early 2014.
All the external drives are without power cables, only USB to the computer/USB hub.
 

Elrich

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By the way, I've found that a non-powered dongle-type USB hub has the same problem. Another one that USED TO work. I plugged it into the Mac, and then plugged one external hard drive into it. The fan in it started up, but it didn't mount.

I really think it's a problem with the Mac somehow no longer being able to provide enough power via a USB hub. It can provide SOME, but not enough to fully power even one device.
 

Cory Cooper

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OK, thanks.

When you use a powered hub, it is supplying the power for anything connected to it, not the Mac. Since the external drives are small portable enclosures, they are receiving power from the USB connection. You cannot connect most bus-powered USB hard drives to a non-powered passive USB hub, as they will definitely not receive enough power, especially if more than one. Also, it isn't recommended to connect more than one bus-powered USB drive to a portable Mac, especially if it isn't connect to AC power.

I assume the MBP is connected to AC power when you are connecting the USB hub and drives?

C
 

Elrich

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Yes it is.

I'm embarrassed to report that I found the problem -- the USB hub's AC power cable was only partway inserted into the hub. Once I found that, it started functioning normally again. I guess, that, after the old hub apparently died, I was primed to think that the new hub's not working was ALSO not some lamebrained cable-connection issue. But it was. Sorry about that!
 
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Cory Cooper

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No worries at all...glad you found the solution.

Measure twice... ;)

C
 

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