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It's the one dead center of the circle that exploded. I was thinking it was either a diode or a capacitor of some kind, but I don't know how to tell its value from its markings. This picture is of a motherboard that came out of an Acer netbook (Acer One D255E). I'm assuming that the wrong type of charger was plugged into this netbook to cause the damage. This also seems to be the only noticeable damage. Does anyone have experience with repairing this? Or at least what it is?

enter image description here

If any more info is needed just ask.

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    \$\begingroup\$ It looks like a capacitor. \$\endgroup\$ – Toybuilder May 23 '11 at 22:04
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It looks like a tantalum capacitor to me. It's the wrong shape for a diode, and they usually have the cathode marked with a line.Tantalums usually have the positive terminal identified with a line or a '+' like that, and are encapsulated in plastic. Electrolytics usually have the negative terminal identified with a line, and aren't usually encapsulated.

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    \$\begingroup\$ Note that all the designators in this section of the board are prefixed with "P". e.g. PQ23, PJ2, PC44. My guess is the board is so large that they didn't want to get into designators like C1044, so they broke the board into sections and prefix P so they could reset the designator count. \$\endgroup\$ – ajs410 May 23 '11 at 22:32
  • \$\begingroup\$ Oh, I didn't know they did that. Makes perfect sense. \$\endgroup\$ – Xxajr8xX May 23 '11 at 22:59
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    \$\begingroup\$ Maybe the bad power supply had the polarity switched-- tantalum caps explode if you get the polarity wrong. \$\endgroup\$ – pingswept May 24 '11 at 13:32
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    \$\begingroup\$ Agree with @Leon, that's a tantalum capacitor. I disagree that the polarity was switched; more likely, overvoltage killed it. The cap is probably across the output of a DC-DC buck converter in which the series MOSFET has failed. (Those large surface-mount inductors are screaming 'buck' to me.) Excessive input voltage could definitely be the cause. \$\endgroup\$ – Adam Lawrence May 24 '11 at 16:40
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Definitely a capacitor - could be tantalum or aluminium polymer - the latter are being increasingly used due to ultra-low ESR.

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