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Win7 USB external drive drops out, then reappears


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I've received some excellent virus/malware help from these forums, so I'm hoping some of you computer uber-gods can shed some light on an issue I'm having (non-virus related, I think).

I'm having an annoying problem on my Win7 Pro 64 bit home theater PC (HTPC) that i use as my DVR to record TV running Windows Media Center (WMC). The WMC part works wonderfully-- check it out if you're unfamiliar with it.. it blows away the DVR offerings by both DirecTV and Comcast (I've had both). But I digress...

I thought that since this computer is always on, why not attach my Seagate 2TB Expansion Drive to the PC's USB port, share the drive at the root as Z: and map network drives to it on my other household PC's to have them all run periodic backups during the wee hours of the night, saving the disk images to this Seagate hosted on the HTPC.

The HTPC will "trumpet" every 10-15 minutes (making the sound that removing a device makes, followed in 10 seconds by the adding device sound). Upon watching this in detail, I've caught the Seagate light turning off when the first trumpet sounds, and the light coming back on at the second trumpet 10 seconds later. Further watching shows the drive Z disappear from the list of drives under Computer, then reappear 10 seconds later.

So the HTPC is dropping the drive, then re-adding it 4-6 times per hour. Every once in a while the sharing on the drive is blown away too and I find I have to reassert the share.

The goose chasing I've done so far:

About the time I hear the trumpet the Event viewer, Windows Logs, System shows a series of Service Control Manager Event ID: 7036 's

The Multimedia Class Scheduler service entered the running state.

and then 10-12 seconds later

The Portable Device Enumerator Service service entered the running state.

120 seconds after the Enumerator starts, it enters a stopped state and then a couple minutes later the Class Scheduler stops as well.

All of this will repeat 15 to 20 minutes later, so you can imagine what my event logs look like.

Does any of the above ring bells for anyone reading this?

I've moved the Seagate drive to a 2nd Win7 Pro PC and it does the exact same thing, so I'm concluding that the USB port in the HTPC isn't bad, although I've plugged the drive into several of its USB ports and see no difference in behavior.

I've checked with Cetoncorp.. the folks that make the InfiniTV 4 tuner card for the DVR function that Win Media Center uses and they advise the following:

I wish we had better news for you... However, the InfiniTV/Software/Driver/Etc does not start/stop/interact with the Multimedia ClassScheduler Service.

I've installed the Process Monitor tool from Microsoft sysinternals but I'm a bit blown away by all the info it displays. (i.e. a powerful table saw in the hands of an amateur makes more sawdust than fine cabinetry... ;-)). I'm under the impression that this tool can show me the calling process that gooses the Multimedia Class Scheduler to wake up, but I'm not sure how to do that, or if this is even an appropriate avenue to pursue...

There is a small second partition on the Seagate (I'm not sure if it was there from the factory or not) that Bit Locker errors come up for after a reboot...

Event ID: 24620 -- Encrypted volume check: Volume information on \\?\Volume{27395a8b-d4b8-11e0-95cb-806e6f6e6963} cannot be read.

This isn't a boot drive, but perhaps the drive was attached at some point during a Win7 setup and it received one of those special boot partitions that Win7 throws down maybe? I didn't want to nuke the partition before investigating this further, but I certainly could if you folks think that this behavior is Win7 rechecking this drive all the time. But the Bit-Locker errors only occur right after boot... not continually like the 7036 events I'm seeing with the drive dropping out/reappearing. I'm not sure if Win7 comes back every 15 minutes to check a partition that it couldn't read? And if it did, wouldn't I be seeing continual Bit-Locker errors?

Any ideas on how I should proceed to track this down?

I'm close to destroying the case of the Seagate, yanking out what I expect to find being a 2 TB 3.5" SATA drive inside it (hopefully a Seagate or Maxtor.. LOL), and mounting the drive into the HTPC and directly attaching a SATA cable to it to eliminate the USB interface. Yeah.. I know... it will be faster too... but i do lose the portability of the drive doing this.

Anybody wanna help me beat this one into submission?

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First guess is that it's your power settings. Power settings have the ability to shut devices down when they are "Not in use" to conserve power. If you aren't running on High Performance, switch and see if the problem continues.

Thanks for the reply, rgabbard! Good thinking, but already covered... my bad on failing to mention this in my "what I've done already" section.

I'm running the Maximum performance selection, with sleep disabled in all advanced options within that scheme. I also went into device manager, USB ports and unticked "allow this device to put the computer to sleep" under the power management tabs on the USB hubs (basically, anywhere where i saw power management options, I've turned 'em off-- 4 places on one machine's USB devices, 6 places on the first machine).

I've done the above to both computers, and neither shows any sign of it making a difference in the odd behavior.

What's your next thought?

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I had this issue one time, turns out in my case the usb cable I was using was too long, I used a shorter cable that actually came with the drive and it worked.

I appreciate the reply, Firefox!

I'm still running the original USB cable that came with the device.. a 5 or 6 foot USB A-male at the computer end with a micro (or mini ?) USB (sorta looks like a miniature version of the standard HDMI connector) at the drive end.

I don't have another one of these cables to substitute, but may go out looking for one just to eliminate the possibility of a bad cable. But I've changed ports, reseated connectors, and moved the drive quite a few times and the errant behavior never seems to change-- even moving it to a 2nd computer.

With the behavior being so "scheduled" looking, with it occuring every 10-15 minutes, isn't it hard to believe that a hardware problem or cable could be the cause? My experience with hardware failures is a much more "random" appearance of the issue.

I do have a 3rd Win7 machine (not running any media center) as well as an XP Pro laptop... they are perhaps next in line to meet this disk just to see if the problem follows the disk drive...

Very perplexing!!!! Please keep the thoughts coming... I'll try anything possible (erm... within reason, of course)!!! ;)

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Go ahead and find another cable. In my case the cable that came with the drive was a short 1 foot long cable. I was using a 6 foot on most of my computers, but when I used that 6' cable on my laptop it either would not see the drive or it would go off line. I started using the 1' cable on the laptop and have not had issues since then.

Not saying that will fix yours but its worth looking into it.

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Go ahead and find another cable. In my case the cable that came with the drive was a short 1 foot long cable. I was using a 6 foot on most of my computers, but when I used that 6' cable on my laptop it either would not see the drive or it would go off line. I started using the 1' cable on the laptop and have not had issues since then.

Not saying that will fix yours but its worth looking into it.

Well, I borrowed a cable from the neighbor and it behaves the same way... drive disappears, reappears just like the first cable. He gave me two, so on the weird chance that his first cable is bad as well, I'll try his second one now...

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3rd cable in place, no change in symptoms.

I even plugged the 3rd cable into a different USB port... the multimedia class scheduler service pops up in the system event log about 17 minutes after the drive was plugged in and the the cycle repeats.

I can't believe three different cables could be bad, right?

I guess next move is to shift the drive to another PC and see if the symptom follows...


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Yup.. separate power source on the external drive so it's not dependent upon power from the USB connection.

The fact that it happens with all 3 Win7 PC's that I've connected it to, along with 3 different cables, coupled with the 15-20 minute repeatability really convinces me that its not its not a hardware/power issue.

I've moved the Seagate drive to a Windows Home Server 2008 setup as a data storage drive... it seems to be working swimmingly in this capacity (I'm pretty sure WHS 2008 is based upon Win Server 2003 technology). In fact, it worked so well on the WHS that, along with my curiosity over the innards of the drive, I cracked the case open and found a 1.8 TB Seagate SATA drive inside. I threw the drive into a Rosewill USB SATA dock which effectively replaces its USB interface and plan to procure a PCI to SATA interface for it because my WHS PC doesn't support SATA (just IDE).

As for progress on the original issue, I have another external USB hard drive that I'm about ready to connect to one of the Win7 PC's to see if it, too, does the disappearing act...

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