OopsBackwards9631While working on stuff for the upcoming Tiny85 class, I accidentally plugged one in backwards.  After I heard the little “poof” I unplugged it and tried to pry the chip out before I realized it had gotten hot enough that all the solder connections were still molten and the socket was coming out of the board.

You can see the spot on the top of the chip where all the magic smoke escaped.  You can maybe convince yourself you can see the pin-1-end notch in what’s left of the socket – and the pin 1 dimple on the chip.

I was trying to program the ’85 with an ArduinoISP at the time of the incident.  The good news is that both the Diavolino and the USB-serial cable powering it survived even after delivering enough power to do the damage shown.

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2 Responses to Oops

  1. Saga says:

    Hi Jim, by chance are you the Jim from W88? 🙂 I wanted to find out a little more about the Tiny85 and one of the top search results from Google was this site.
    Ok, so now I’ll share my Oops with you. Many decades ago when I was Product Manager for an 8 bit ISA Coax Ethernet card the company got us 4 samples of the “pump” (5vdc to -9vdc converter) from Taiwan at $25 each.

    While the pumps that we had had an asymmetrical pin out (impossible to plug in backwards) the Taiwanese product had symmetrical pins. I was not able to distinguish pin 1. What I did was to see how the labeling on the original pump was laid out and aligned the Taiwanese pump so that the text was aligned the same way. I connected the LAN board and powered up.

    Poof! Oops.

    One $25 pump gone. Of course management was not too happy about me frying the pump. I got a second pump and plugged it in in the opposite direction and the LAN board went along in its merry way. Best wishes.

  2. Jim says:

    Hi Salvador,

    Yep, it’s me. And I’ve blown up employer’s stuff with even less justification than your very reasonable text orientation explanation. I hate when that happens.

    My other recent ‘backwards’ incident wouldn’t have let the magic smoke out, but still would have been frustrating: On the Thotcon badge project, there’s a 32KHz crystal in a small rectangular SMT package. There’s a chamfered edge on one short end and a typical dimple in the corner on the other end. I was assembling a board and would have put money on the dimple trumping the chamfer to mark the pin 1 end, but I would have been wrong 🙂 Fortunately the pinout was asymmetrical, with the crystal across the 2 pins at one end and the other 2 shorted. An ohmmeter check showed which pins _couldn’t_ be the crystal. And the ohmmeter even trumps the dimple 🙂


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