Super User is a question and answer site for computer enthusiasts and power users. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I have an Amilo Pro laptop with an attached HDD in external USB enclosure. I can't reliably shut down my laptop, and sometimes, I can't start it when the external drive is plugged in. Rarely, my laptop doesn't start at all even after I unplugged the device. I have to power cycle several times before it is willing to start. When the computer is running, everything seems to be fine.

I deducted the problem to the USB connection, as it seems to power-back my computer through the USB's 5V wire, which might lack protective diodes, causing the machine's BIOS to be confused. My questions are:

Is this back-powering property general - e.g. should I buy a new rack to solve the issue?

Does this 5V damage my laptop in any way?

Follow up to my previous question

Update from my comments:

Sorry about the terminology, I have 500GB SATA HDD in a rack, which has its own power supply and a USB cable to plug it into a computer - the OS sees it as jet another HDD. My laptop worked fine before I purchased this external device. It is a Spire GigaPod VIII

It is directly attached to my laptop. It is independent which of my 4 hubs I plug it in. No video at all - I guess the BIOS gets confused about the power status in the system. It seems I have to unplug the cabel, replug the laptops own power cord and then it is willing to start up.

It works without problems. Only at shutdown and startup causes it trouble. If I manage to turn on the laptop, everything works fine, file copy, running programs from it, all. I already filled it with 250GB of stuff and backup.

So, how it seems to work: Before shutdown, I unplug the device without warning - no eject by OS - then perform shutdown. Power on - works - I log in and then I attach the enclosure - HDD works. The strange thing is that it is not enough to unpower the enclosure and leave it plugged in.

If I shutdown 'properly' it powers back. If I eject the drive then unplug it and shutdown, 50% it won't start the next poweron - I have to plug the drive back, powercycle, unplug, powercycle x2 then it starts up. If I just simply unplug, everything shuts down and starts as expected. I checked my windows USB power report, it says two mass storage devices cosume 2mA + 200mA.

Update 2

I forgot I have a 2nd 15GB IDE HDD (from my old times) in a different enclosure. No shutdown/startup problems with that (I'm relieved)! It seems I have to try a different SATA enclosure for my 500GB HDD.

Update 3

Changed the enclosure to a different vendor, and it seems the error has disappeared. Thanks.

share|improve this question
up vote 0 down vote accepted

What exactly is a USB rack?

I have never heard of a laptop being able to take power from USB to power anything in the laptop. I think your laptop has either power supply issues or motherboard issues. As you stated below, this leads me to believe that it is a power supply or mb issue.

Rarely, my laptop doesn't start at all even after I unplugged the device.

I could see a laptop being damaged if somehow power was sent back through the USB connection, but that is not how it works most of the time. Any more details on this rack device?

EDIT: You sound like you have a USB hub in between the external hard drive and the laptop. Is this correct? Some devices do not like certain USB hubs/port splitters, especialy the ones that do not provide any extra power. It sounds like this one is powered maybe? Does the hard drive work ok plugged in directly to the laptop? Does it act the same way no matter which USB port on the laptop it is plugged into?

EDIT 2: Ok, sounds like you just have an external hard drive enclosure. I looked up that model and saw what you mean. That drive has it's own power supply, so it should not have any trouble getting a signal from the computer. Beside the powering up issues, does it work fine otherwise?

share|improve this answer
oh, ok. When you say it doesn't power up, where does it hang up? Do you even get video? Does it hang at a load screen? – Troggy Aug 24 '09 at 16:13
That is possible I guess. The reason I asked about the startup is I thought maybe the BIOS was looking for usb devices to start off of before it trys the internal hard drive. – Troggy Aug 24 '09 at 16:24
Do you have to "unplug the device without warning - no eject by OS" everytime? What happens when you properly start and shutdown everything? – Troggy Aug 24 '09 at 16:28
When everything works properly, can you use the external hard drive just fine? copy files to and from the hard drive? – Troggy Aug 24 '09 at 16:34
I've re-tested a lot of combinations but still it seems, the 5V coming from the USB cord is causing a power anomaly in the laptop. So my question is: should I buy a different vendor's enclosure, look for a cable without the 5V wire? – akarnokd Aug 24 '09 at 17:07

How about you plug your USB HD to the laptop USB port directly without that "rack"?

Most USB devices won't let the current to go backwards to the +5V its USB port as far as I know.

share|improve this answer

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .