Let me begin by acknowledging that I have little practical experience with electronics and that I am entirely responsible for all of the consequences of my actions. I was careless.
This story begins where the shelf story ends. I wanted to move a couple of hard drives off my desk down onto that shelf, an easy thing to do requiring no particular skill. But I also wanted to do a little tinkering and satisfy my inner lazy lout by putting switches for the drives within easy reach.
Which I did. Before we go any further, let's inventory the parts, shall we?
Inside the enclosure, we have a power connector (with 5v, 12v, and two ground wires) and a data connector (IDE). Both completely standard, as far as I know. You can pop any IDE drive in there and it'll work.
Outside, we have a power connector and a USB connector.
The USB cable is completely standard, one of several standards in fact, but they can all be distinguished by different connectors, I believe.
And finally, we have the power cable. It's a standard size and shape, a shape designed to guarantee that it can only be connected in one orientation. It has six wires, two for ground, two for 12 volts and two for 5 volts. The power brick on the other end of the cable is also apparently standard, at least all the ones I have deliver 5 and 12 volts at 2 amps.
I took a couple of bricks from some old USB enclosures that I bought on the cheap from eBay, cut the cable on the DC-side of the brick, wired in my switches, and put everything together.
Reluctant to assume that I'd got the soldering and wiring right, I plugged a drive (one that I've abandoned due to read errors) into one of the USB enclosures from which I scavenged the bricks, and flipped the switch. The drive powered up. I plugged in the other brick and flipped the other switch. The drive powered up. Everything seemed just dandy.
I moved the real drives down to the shelf, got everying nicely stored, used some zip ties to keep it neat and tidy, and powered up the real enclosures.
Nothing. Nada. Bupkis.
Odd, I thought, since it worked a minute ago.
I put the first enclosure back on its original power supply and fired it up. Worked fine.
I put the second enclosure (the one with two drives, a half-terabyte and another 200G) back on its original power supply and fired it up.
Nothing. Nada. Bupkis.
Now I take a really close look at the various and sundry bricks I've got. Guess what I discover. Go on, guess.
While the power connector is a standard shape and size, has a standard number of pins, and delivers standard amounts of power, the actual pins used differ from one brick to another.
On one enclosure, I've transposed 12v and ground. On the other, I've transposed 5v and 12v.
At this point, I'm feeling a bit of pain and remorse. I'm also feeling pretty stupid. And wondering by what miracle of chance I've never before plugged the wrong power brick into an appliance.
The pain and remorse take on a kicked-in-the-stomach sort of quality when I discover that I haven't damaged the enclosure, I've fried both drives. Put in another enclosure, the half-terabyte drive spins up but is never seen by the computer; the 200G begins immediately to smoke.
The real kicked-in-the-balls agony begins when I realize that the larger “backup” disk in fact contained the only copy of a bunch of video data.
Repeat after me: a backup disk is not a backup if it contains the only copy of your data.
A short drive and $150 dollars later, I have a new half-terabyte of disk and I've retrieved my offsite backups. The video data is not on them.
Several hours later, I have restored all of the video data off the original MiniDV tapes. I will not have to explain that I've lost all of the video footage from Egypt.
The day is shot, but several valuable lessons have been learned.
A backup is not a backup if it is your only copy of the data.
Just because things look standard doesn't mean they are. Always check.
Fuck up in software, your software won't run right until you fix it.
Fuck up in hardware, your hardware won't ever run again.
Here's hoping someone out there can learn them vicariously.