External hard drives no longer visible

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A couple of days ago I went to eject my Time Machine backup disk and couldn't see it either on the desktop or in Finder.

When I unplugged it a message came up to say something along these lines:
It is taking up too many resources so has been disabled.

I thought no more about until I reconnected it the following day and couldn't find it. As it had been very warm when I had previously disconnected it I assumed that it had failed.

I have now connected the drive I used to download all the documents from my old PC and there's no sign of that either.

Presumably all external drives have somehow been disabled. Can anyone help please?
 
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Are those external drives powered (have own power supply)

(standard tech answer to everything, I know) but have you restarted the mac since disconnecting the drives?
 
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More re external drive not visible

The wording related to this problem is:

"Because a USB device was drawing too much power from your computer, one or more of your USB devices have been turned off".

The following para reads:

To prevent damage to your computer, the USB device has been disabled. Other devices may also have been disabled. when you disconnect the device drawing too much power, your other USB devices will be ebabled again.
 
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I have an external port hub which is powered. I have just disconnected my Time Machine drive from the hub, disconnected the hub, and connected the TM drive directly to slots on my Mac. That's when this message came up again.
 
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chas_m

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I had this happen to me using a "powered" hub. I put the "powered" in quotes because after being dumbfounded for a few minutes, I discovered that a recent move of the hub for dusting purposes had jiggled the power cord just enough to loosen it from making a good connection. Mystery solved.

Perhaps the same thing is happening to you.
 
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I'm a newbie to the Mac world, so, I feel your pain! On almost all computers, regardless of the platform, an external drive should always be plugged directly into the computers usb slots. This would seem to not be necessary since the items supply their own external power in most cases. Printers, mice, keyboards, speakers, etc.
can almost always be plugged in to the usb hub. The problem now is how to restore the drive as a recognized Volume in the Mac OS after it has been removed. Unfortunately, as a newbie, I don't have that answer. I'm simply trying to clarify what you're saying to the great Mac geniuses here on the Mac Forums. And, believe me, they can be geniuses. They have helped me more than once in this two month world of learning to work with a Mac.

Arthur
 
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MacInWin

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The wording related to this problem is:

"Because a USB device was drawing too much power from your computer, one or more of your USB devices have been turned off".

The following para reads:

To prevent damage to your computer, the USB device has been disabled. Other devices may also have been disabled. when you disconnect the device drawing too much power, your other USB devices will be ebabled again.
The Mac detected too much current draw from the USB port and shut it down. Disconnect it and connect it to a powered hub. It should reappear, although you'll probably have to run Disk Utility to fix any problems coming from the shutdown.

If disconnecting it doesn't fix the problem, disconnect ALL of your USB devices and then connect them again, one at a time, until you get the message again. That last one you connect before the message appears is the guilty culprit.

The science is that USB ports, by definition, only provide a maximum of 500 mA of power. When you exceeded that limit, the Mac shut the ports down. As long as you continue to draw that much, it won't come back on.
 
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I had this happen to me using a "powered" hub. I put the "powered" in quotes because after being dumbfounded for a few minutes, I discovered that a recent move of the hub for dusting purposes had jiggled the power cord just enough to loosen it from making a good connection. Mystery solved.

Perhaps the same thing is happening to you.

I don't think there was a problem with powered hub but I have tried connecting directly to Mac's hub. One external drive can now be seen but I can't write to it and I can't copy and paste to it. The Time Machine drive may be kaput.

How do I restore functionality?
 
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It lloks as if the reason I can't write to the external drive that I can see is that it's formatted for Windows so I can only download stuff from it unless I go into Bootcamp.
 

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