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I'm taking apart a misbehaving USB hard drive, and I've spotted a broken component on the PCB for the hard drive itself. Fortunately, there appears to be an intact, identical component on another part of the board, but I can't identify it.

The code on the top isFBD (sorry for the awful phone picture), it appears to have two connections, has been deliberately surrounded by a ground trace, and is 4.9 x 2.3 mm

enter image description here

enter image description here

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  • \$\begingroup\$ That might be an SMD fuse. \$\endgroup\$ – Vladimir Cravero Dec 29 '15 at 13:05
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    \$\begingroup\$ What did you do to the poor little thing to blow the lid off? \$\endgroup\$ – jippie Dec 29 '15 at 13:06
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    \$\begingroup\$ Don't see why an SMD fuse would need a guard ring... oscillator resonator MAYBE but more likely some kind of sensor ... vibration perhaps? the odd mounting angle must be significant. Do both sensors point towards the platter centre? \$\endgroup\$ – Brian Drummond Dec 29 '15 at 13:12
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    \$\begingroup\$ I bet the guard trace connects to a buffered output ... probably one of the SOT23 pins. \$\endgroup\$ – Brian Drummond Dec 29 '15 at 13:14
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    \$\begingroup\$ Be aware that any of the parts it could be (see also Olin's answer), due to prior elimination steps above, are very unlikely to die at all, let alone in such a violent way. So you must be absolutely aware of the high likelihood that something else broke first, over-stressing this part. \$\endgroup\$ – Asmyldof Dec 29 '15 at 14:15
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That is a piezoelectric ceramic shock sensor / acceleration sensor, likely made by muRata. I've seen up to 3 of them strategically located on hard drive boards. They are labeled as "SK" on WD PCBs, but aren't labeled on Maxtor HDs. Here are links for info and 2 datasheets:

https://www.murata.com/en-us/products/productdetail?partno=PKGS-00GXP1-R

https://www.murata.com/en-us/products/productdata/8797617225758/00GXP1-E.pdf?1452655830000

http://www1.futureelectronics.com/doc/MURATA/PKGS-00LD-R.pdf

enter image description here

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I'm guessing it is either a Hall effect sensor or a ceramic filter.

The guard trace around it means this component is sensitive to capacitive coupling from other traces. The odd angle implies it is sensitive to orientation, probably due to magnetic fields since the guard trace should be shielding it well enough from electric fields.

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