11

A dog bit my pendrive and after that I can no longer mount the drive in Linux (Debian-based distro).

I can see the light on the drive blinking and the drive is registered via USB. Is this due to a corrupted file system or is it dead? Is there any way to fix this?

lsusb shows this:

Bus 005 Device 001: ID ld6b:0001 Linux Foundation 1.1 root hub
Bus 004 Device 001: ID ld6b:0001 Linux Foundation 1.1 root hub
Bus 003 Device 001: ID ld6b:0001 Linux Foundation 1.1 root hub
Bus 002 Device 002: ID 046d:c517 Logitech, Inc. LX710 Cordless Desktop Laser

Bus 001 Device 003: ID 058f:1234 Alcor Micro Corp. Flash Drive

The below image lists the disks and partitions on my machine. Unfortunately, Gparted didn't detect the dog bitten drive.

gparted showing disks, partitions

These are the results of mtab and fstab.

mtab

/dev/sdb1 / ext4 rw,errors=remount-ro 0 0
tmpfs /lib/init/rw tmpfs rw,nosuid,mode=0755 0 0
proc /proc proc rw,noexec,nosuid,nodev 0 0
sysfs /sys sysfs rw,noexec,nosuid,nodev 0 0
udev /dev tmpfs rw,mode=0755 0 0
tmpfs /dev/shm tmpfs rw,nosuid,nodev 0 0
devpts /dev/pts devpts rw,noexec,nosuid,gid=5,mode=620 0 0
/dev/sdb6 /home ext4 rw 0 0
/dev/sda2 /media/Disk fuseblk rw,allow_other,blksize=4096,default_permissions 0 0
/dev/sda3 /media/sda4 ext4 rw 0 0
/dev/sda5 /media/sda5 fuseblk rw,allow_other,blksize=4096,default_permissions 0 0
fusectl /sys/fs/fuse/connections fusectl rw 0 0
gvfs-fuse-daemon /home/aswin/.gvfs fuse.gvfs-fuse-daemon rw,nosuid,nodev,user=aswin 0 0
/dev/sr0 /media/ISO iso9660 ro,nosuid,nodev,uhelper=hal,uid=1000 0 0

fstab

# /etc/fstab: static file system information.
#
#                

proc    /proc   proc    defaults    0   0
#Entry for /dev/sdb1 :
UUID=3beb0fe3-d9ff-4f2a-8431-8a7d458e93dd   /   ext4    errors=remount-ro   0   1
#Entry for /dev/sdb6 :
UUID=ae442d7d-895f-455e-b720-22d28f64656b   /home   ext4    defaults    0   2
#Entry for /dev/sda2 :
UUID=5CB00540B00521DE   /media/Disk ntfs    defaults,nls=utf8,umask=0222    0   0
#Entry for /dev/sda3 :
UUID=98cd90c4-f6a6-4a41-b782-92157d460de8   /media/sda4 ext4    defaults    0   0
#Entry for /dev/sda5 :
UUID=3220C4EA20C4B5DF   /media/sda5 ntfs    defaults,nls=utf8,umask=0222    0   0
#Entry for /dev/sdb5 :
UUID=b5fa78c6-8dc5-4451-9c60-a3528cfdcfc7   none    swap    sw  0   0

This is the thumb drive that suffered dog bite, if it matters at all.

usb stick with dog bite

A closer look at the dog bitten pendrive:

dog bit pendrive up closer

  • If the contacts/leads were broken, you may be able to solder them back... – Keltari Nov 21 '13 at 15:08
  • 1
    If lsusb shows everything OK but mount fails, I think recovering that filesystem would be very painful. – 174140 Nov 21 '13 at 15:14
  • 2
    Looks like you have a short. Your are going to need to fix that. You need a fine pointed solder iron. It almost looks like you could just remove the solder. – Zoredache Nov 21 '13 at 16:37
  • 1
    What breed of dog? (sorry couldn't resist). But on a more serious note, I feel the value of SE is in questions that can go strangely deep into all areas. – Rajib Nov 21 '13 at 17:11
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    I'd definitely get the data off that drive and retire it. Seems to make an excellent chew toy. – a CVn Nov 22 '13 at 12:47
12

The pictures show that soft(er) solder has been squished/moved under pressure, causing undesirable cross connections.

The one section would be able to be cleaned up with any half descent soldering gun, and some "solder wick". enter image description here Solder wick is a fluxed braid of flat copper. In this situation it would be a good method to remove the small ammounts of solder.

Heat the wick on top of the solder you wish to remove, slide wick to new area of the wick (as it fills), and slide across intended removal areas. That method could clean something that small of the solder fairly easily.
Done carefully the solder in the undesired connections would be removed. Then some hope that it was the only problem.

  • Normally it will not be necessary to use the solder wick as the solder will go back to the original place after melting thanks to the surface tension. --- Even easier could be not use a solder gun at all. As the solder was deformed in the cold state it could be most probably removed in a cold state too just by careful cutting and scratching by a sharp knife. It is described in the reply of Jon Ruttan. – pabouk Dec 20 '13 at 9:16
6

Your dog's bite deformed some of the solder on some unused contact points, and the circuit is shorting out. If you can sever these accidental shorts, you might be able to get the unit working again. Any means of removing the solder from between those contact points you've zoomed in on in the second image should work.

Solder is a soft metallic alloy, and utility knife with a very sharp blade, such as an X-Acto knife, can usually slice through the solder. Normally, you should be careful not to cut too deeply, which would damage the board below the solder, but in your case, the section that's been damaged isn't actually used, so even if it got damaged a bit, as long as it doesn't short out it should be okay.

The circuit board is built up in layers, starting with a rigid, non-conductive support layer. A layer of conductive copper-based metal foil is adhered to that layer, and the metal foil is then etched away in patterns so that when the etching is done, the foil will act like a whole bunch of little wires. To protect those wires a layer of non-conductive enamel is painted on (coloured green in this case). Wherever those little etched wires need to connect up to an electrical component, such as the USB controller chip, RAM ICs, or the USB connector, there is a larger section of the copper foil left during the etching stage, and no enamel is painted over those particular points, providing a pad for the component to sit on. To glue the component to the pad, a conductive metal alloy with a low melting point, called solder is melted to both the metal in the component's leads and those pads. If a blob of solder is big enough, or as in your case gets deformed, it can accidentally connect two or more of those pads together, creating an unexpected circuit configuration. This bridge between the two pads needs to be broken.

Any means of removing the solder forming those bridges should fix your pendrive.

If you do use a utility knife, try not to cut into the enamel below the solder bridge. If you do, it won't break anything, but it may expose the wire beneath it a bit. If the cut is deeper and severs a copper etching, normally it might break something, but from what I see in the image you've provided, it probably would be fine.

3

The pen drive solder connections are shorted and can easily be removed. No need for a soldering gun which could damage the copper pads on the PCB as well as overheat the electronic components on the board. The solder contacts are small and a low wattage soldering iron in the 25-35 watt range is more than adequate.

You may not need the soldering remover wick. Using a soldering iron, briefly heat each pad to liquefy the solder and wipe the liquid solder off with an abrasive cleaning pad (Scotch-Brite). Visually inspect for any remaining solder and repeat if necessary. Avoid overheating any one pad by skipping a pad between each desoldering step, i.e., desolder 1,3,5,7,etc then go back and desolder 2,4,6,8,etc.

1

This happened to a friend of mine. The dog's tooth had penetrated just enough to deform the circuit board and damage the tracks - too fine to be re-soldered. The damage was just enough that the light still flashed and the drive partly functioned - similar to your description.

By taking the board out of the housing, it was possible to sandwich it between two non-conductive sheets of plastic. Rebind in the housing and tape tightly with gaffer tape to keep it firm.

This held the board rigid enough for the data to be recovered.

You may be lucky!

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