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Device removal

 
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maurice
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PostPosted: Sun Dec 18, 2011 7:28 pm    Post subject: Device removal Reply with quote

Hi, I have an external HD and a USB key connected to my Intel Mini via a powered hub. When I close down at night everything switches off and when I power up in the morning both devices switch on and are functional.

However, occasionally, one of the two switches itself off and I get an alert "Device removal" warning me of the danger of removing a device before closing it down properly. Actually I didn't remove anything. It happened by itself. I used a powered USB hub to avoid this sort of things.

What can I do to prevent this nuisance? and was I mistaken in believing that these devices are Plug N Play?

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Bandit Bill
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PostPosted: Sun Dec 18, 2011 7:40 pm    Post subject: Reply with quote

First of all, you need to figure out which device is causing the issue. My guess is... the hard drive. I'd unplug the USB stick for a while and if the issue still exists. If it is still happening, then likely the hard drive is causing the issue. Likely it is sleeping and un-mounting in the process.
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maurice
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PostPosted: Mon Dec 19, 2011 12:08 am    Post subject: Reply with quote

thank you for the hint. I will try it.
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Cypher
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PostPosted: Mon Dec 19, 2011 4:52 am    Post subject: Reply with quote

I had a similar thing a few years ago, and the most noticeable symptom was my external usb audio (going to headphones) skipping or switch off completely and the iMac to divert back to system audio and I was also getting the device removal warnings.

I had quite a few things plugged into a 7 port powered hub so there were plenty of devices which could have been causing it. The problem was completely intermittent and random so difficult to pin down, I tried unplugging device after device which was a very time consuming and I spent a lot of time going round in circles. To cut a long story short mine turned out to be the usb hub.

Try plugging your devices directly to your iMac and miss out the hub if possible it might save you a bit of grief.
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maurice
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PostPosted: Mon Dec 19, 2011 7:18 pm    Post subject: Reply with quote

It is impossible to plug all the USB devices onto the Mac (Intel mini, in my case). The idea of a powered hub was to prevent drawing too much power from the Mac. What causes a device to disconnect itself? It has been suggested that an external HD may go to sleep, but surely not a USB key?

Also, when I select my USB key and press Command E, its icon disappears, but as soon as I pull off the key I get the alert "Device Removal" Can anyone confirm if USB keys are plug N play, that is: can they just be pulled out of their sockets without the Command E preliminary?
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Cypher
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PostPosted: Tue Dec 20, 2011 4:46 am    Post subject: Reply with quote

I had the same issue with the ports, but I plugged what I could directly into the Mac to rule at those devices. Took a lot of trail and error and the fault came down to the hub.

I always eject drives before unplugging even so called plug and play devices.
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