Does anyone know what this component is on my WR850G motherboard ?

[img]http://i.imgur.com/JFa1e1w.jpg[/img] In the top right corner of the picture, I believe the box is marked S1, and the component says "P185 IR4F". can someone please tell me what it is. A transistor? Resistor? I'm new to all of this and I need to replace it because it's completely burnt out on... show more [img]http://i.imgur.com/JFa1e1w.jpg[/img... In the top right corner of the picture, I believe the box is marked S1, and the component says "P185 IR4F". can someone please tell me what it is. A transistor? Resistor? I'm new to all of this and I need to replace it because it's completely burnt out on my router. I've tried googling it but to no avail. I can not find this part anywhere and it would help if I knew exactly what was and it's purpose.
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