A Lesson Learned the Hard (and Expensive) Way

The following is from Gary's Blog on EEWeb.  Think you know what happened?  Click the link at the end to read the read of the blog and learn an important lesson.

How to Destroy Data and Hardware, Wholesale.

So a nice holiday weekend, I decide to reorganize my home office and set up some extra equipment I had sitting around. I pull everything out, unplug all the cables, and dress everything up nicely. I add a network hub, and set up an old PC that I use occasionally, and added the power wall wart to the USB hub I’d been using. Also fixed and set up a scanner. It all looked great and I had more workspace as well.

After that, I did have a few hours of work to do for a client, and the latest files were on a thumb drive so I plugged that in and sat down to work. Odd, it doesn’t recognize the thumb drive. I try another one, and it doesn’t see that one either. Hmmm, no external USB HD as well. Plugging directly into the PC USB ports doesn’t work either, but my keyboard and mouse are working OK. Ah, I think I’ve heard of this – Win 7 not recognizing USB mass storage devices. A quick check of the Googlenet, confirms that this is probably the problem. Unplug everything, reboot, uninstall/reinstall drivers. Nope. Roll back the last Windows update. Nope. Stumped.

Well, it’s getting late, and I have work to do, I can get the files off the thumb drive on another PC. Plug it in, and* that *PC doesn’t recognize it either. Same for the other thumb drive. What the flock is going on!


Think you have the answer?  Read the rest of the story.



Posted: 6 years 6 months ago by MrDEB #8489
MrDEB's Avatar
Am sure this is not the first time someone has used the wrong wall wart.
Perhaps a color code for the barrels is a solution?
Posted: 6 years 6 months ago by W4GNS #8494
W4GNS's Avatar
Or take 3 seconds to verify what you're doing
Am sure this is not the first time someone has used the wrong wall wart.
Perhaps a color code for the barrels is a solution?
Posted: 6 years 6 months ago by Jon Chandler #8495
Jon Chandler's Avatar
I've been a victim of this...

I bought a nifty USB DVD drive at Goodwill. It came with a wall wart attached to it.

My partner was installing some new software on his new tablet computer that didn't have a optical drive. Rather than going through the network, we connected the external drive using the USB cable. It was working but it seemed slow so I speculated that it might operate better with the power supply connected.

POP went the drive and a tiny whiff of smoke came out of the new tablet. What the heck?!? Turns out the power supply that had been cabled-tied to the drive from Goodwill was a 12 volt supply and didn't actually go with it! The drive was destroyed. Fortunately, despite the whiff of smoke, the tablet seemed to work fine. Lucked out that time!

Months later, we opened the tablet to replace a defective keyboard. There was a big charred hole near the USB connectors where some protective device had sacrificed itself!

Always check both the voltage and polarity when you can. Many manufacturers mark the case but not all of them. One of my frustrations is when the circuit can tolerate either polarity but this isn't indicated anyplace. I've torn a few devices down to determine the needed polarity only to find a bridge rectifier so polarity doesn't matter. Nice design. Nicer still if it was marked on the case.
Posted: 6 years 6 months ago by be80be #8501
be80be's Avatar
I had I good one last week I was playing with some leds and using just the voltage it takes to light them. Not a problem,I figured I would try the same thing with just one of them bad idea the dang led went off like a bomb imbedding a piece of it in me.

It happen so fast I couldn't turn the power supply off.
Posted: 6 years 6 months ago by W4GNS #8502
W4GNS's Avatar
Sounds like safety glasses should be mandatory in the be80be laboratory

I had I good one last week I was playing with some leds and using just the voltage it takes to light them. Not a problem,I figured I would try the same thing with just one of them bad idea the dang led went off like a bomb imbedding a piece of it in me.

It happen so fast I couldn't turn the power supply off.
Posted: 6 years 6 months ago by Jon G #8512
 Jon G's Avatar
Oh man. I can't help but feel horrible for the guy... I've had my fair share of complete and total losses, but generally they can be chalked up to something outside my control. To realize later he's happily (yet unknowingly) frying his drives would be... Something would get thrown at the basher residence!

You know what though? Most small USB hubs have these little jacks on them for power and most of them don't say on the hub what polarity and voltage they expect. Obviously, 5V would be a good plan, but what about the polarity?

Someone should invent "USB Protectors"

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