Sometimes, the smoke really does come out!

Samsung Hard Drive showing zener diode regulators near the SATA power connector

An old joke in the computer and electronics technical communities is the idea of “magic smoke”.  The joke is, electronic components have magic smoke in them.  Overheat and let out the smoke and the component (and usually the device!) doesn’t work anymore.

I was working on a friend’s computer.  My diagnosis on his only two-year-old HP system was that the motherboard and power supply was defective;  I was certain the motherboard was bad, and could not rule out the PS, so I made arrangements to get new parts.

Motherboard for his gently-used computer:  $350.  So much for that.  We (his sister and I) arranged to get a new machine from Staples and I would migrate the data from his old hard drive.

Until that moment, I had been running his old hard drive on my laptop using a USB to SATA adapter that is often used by hardware techs and there was no hint whatsoever of any problems.  I had no reason to think the HD was defective—I could bring it up and read his files whenever I felt like it.

That changed when I provisioned his new machine, put everything the way he expected it, put his copy of Norton 360 on it, and so forth.  Hindsight says I should have copied his files while the HD was on my laptop but I was thinking “look but not touch!”  I just wanted to ascertain that the HD hardware was good, and the SMART data was fine (it was)—I wasn’t going to tinker with his disk if I didn’t have to.

I spun up the drive with my adaptor and plugged it into his machine.  OK, I smell something hot—the drive is in the palm of my hand because of how my SATA adapter works.  It’s not spinning—another reason I like to (carefully!) have my hand on an HD is because I can feel it spin up, or fail to spin up, or grind the heads.

No activity.  It’s still hot.

My friend and I both notice the smoke.  (“Whoa, Dave, what’s that!”)

I unplugged the disk and put everything away.

This is what it looked like on my workbench:


Vaporized zener diode in Samsung hard drive

In the opening image to this post, you’ll notice two surface-mount zener diodes on a working Samsung hard drive.  These are widely used in computer power supplies and major components such as motherboards.  They are the basis for voltage regulation upon which we all depend on in nearly every electronic gadget.

This hard drive was also a Samsung, which made it easy to compare this drive to one of my good ones.

What happened to the diode in the 2nd picture??

There is solder on the pads where the diode would normally go, so the component was definitely intended to be there.  It was there.

I’ve smoked various broken devices and homemade projects on my workbench at home.  Way back in the days when people first made their own computers in the ‘70s, a popular way to learn how ROMs (Read Only Memories) worked was build your own out of these little glass 1N4148 diodes.  The diodes, when connected, were all “1’s”.  You got “0’s” in your ROM by putting a heavy-duty power supply across the diode in reverse, which would kill it.  You’d see a nice flash of light.  People still call it “blowing ROM’s”.

I’ve never seen components just disappear in a puff of smoke!

But my friend and I just did.

Eventually, my friend got his data from an online backup he paid for when he got the Norton product.   Samsung’s disk business has been bought by Seagate so I may not see another dead drive from them again.

I’ve tried getting an RMA for this drive but Samsung insists it was bought out of market, likely to discourage gray market use.  And discourage me from buying HP, permanently, but that’s another post.  I usually offer the platters from any HD that is out of warranty or cannot be returned to SATV staffers and other people I work for.

My friend will get some platters to use as paperweights or coasters.

2 Comments on “Sometimes, the smoke really does come out!”

  1. Jingos Its Alive says:

    why didnt you try to fix it?
    I had one of these burn on me in a similar manner when the power supply for one of those ide/sata to USB adaptors failed. It (the PSU) went “POP!”. Perhaps a capacitor blew inside it (?). I’m not an electronics expert. Then I smelled some of the ‘magic smoke’ and it came from my IDE 80GB HDD. Like I said I’m no expert I can only attempt to fix obvious stuff and that part was burnt on my HDD. I have a box of old drives and I found a similar part (you call it a zener diode) on an old 2GB IDE drive. I desoldered my burnt part and replaced it with the one off the old drive and bingo! It worked! I couldn’t believe it so I immediately copied off all my data. And I’m still using the repaired drive.
    I guess the zener diode blew like a fuse when the power supply blew. And all i did was replace it like replacing a fuse and back in business. I impressed myself!
    Jingos Its Alive
    Bachelor of Bush Mechanics
    Backyard Electronics Engineer (University of My Place).

    • davidcmoisan says:

      It’s been nine months since I described this, so I’ll answer as best I remember: I measured the resistance across the pads where the zener used to be and it was a dead short. In a typical power circuit, the zener will be connected between a power rail (+5V in this case) and ground.

      If I hadn’t measured any resistance there, I would have determined that the zener just shorted on its own and I would have tried a spare–I have diodes in stock with the approximately same ratings.

      But I had thought at the time if there was a dead short, I would have let the smoke out of some other component. Yeah, sure, I would not have lost anything by trying, but the end would have been the same. As it was the +5V line that was shorted, it was probably the controller chip finally deciding to die from ESD after I’d handled it a few times too many.

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