Purchased a device from an online retailer (fairly well known and reputable), they ship from internationally and often include a local USB wall charger to replace the one in the box of their goods.

Plugged said charger in and it blew immediately. Pulled it apart (because curiosity - it's worth a few bucks so I wasn't bothered to return it). Turns out the control chip (DK112) blew. Had a closer look and noticed something interesting on the underside - does it make sense for that resistor to be there shorting the pins? Worked out that it is between the GND and Collector pins of the chip. enter image description hereenter image description here

Just curious as to whether the fault is in the circuit design or the chip itself!

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    \$\begingroup\$ That looks like a capacitor not a resistor, probably they had some issues (stability or emissions) and bodged it in there. And in general is a resistor not shorting something, because it has a resistance. (Well except a "0-Ohm resistor", but yeah even those have a defined use and are not a sign of bad design). \$\endgroup\$ – Arsenal Aug 21 '17 at 8:35
  • \$\begingroup\$ To reverse engineer the circuit it often helps to mirror the picture of the underside and then draw the component symbols on that. \$\endgroup\$ – ratchet freak Aug 21 '17 at 8:42
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    \$\begingroup\$ Canonical article on the subject of cheap chargers: righto.com/2014/05/a-look-inside-ipad-chargers-pricey.html \$\endgroup\$ – pjc50 Aug 21 '17 at 8:46
  • \$\begingroup\$ The component that failed seems to be the switch-mode chip on the high voltage side. \$\endgroup\$ – ratchet freak Aug 21 '17 at 9:02
  • \$\begingroup\$ Agree upon second look that it is a cap and not a resistor. And yeah, shorting was the wrong term - guess I meant to ask whether it was a bad design to chuck one in there and whether that might have led to the fault. Now seeing that it's a cap it makes more sense for it to be there. Definitely the chip that failed, just wondering if it was likely to have been the chip itself that failed or if there was an issue in the circuit that caused it to short in some way. Pretty annoyed that the retailer I got the device from included such a cheap adapter, I'll be leaving them poor feedback. \$\endgroup\$ – hutcho66 Aug 21 '17 at 10:25

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