Is this a polyfuse?

[skillz21]

I bought an Arduino Mega from eBay. After I bought it, I noticed that it was a bit different to the actual Arduino Mega, in that the USB to Serial converter was different and that there didn't appear to be a polyfuse there. I got it, and had a look, and there appears to be some component there, but it doesn't look like the normal polyfuse on Arduino. Is this component a polyfuse, and will it protect my laptop and the Arduino board if I accidentally short circuit something?

[skillz21]

It is definitely a fuse, maybe a polyfuse, maybe just a cheap one-time fuse.

Any way to find out which? Without actually shorting it?

[skillz21]

Alright. Like the idiot that I am, I tested it by shorting 5v to ground. It still works fine, but I think if I leave the short connected for a while, the polyfuse will burn out, because, as expected, it gets really hot, really fast when shorted. I'm assuming dissapiation is primarily why they make them a larger size?

[skillz21]

Oh... Wait so I can short it indefinitely, and it will be fine?

[T3sl4co1l]

The less damaging way* is to heat it, to about 150C, at which point the resistance should increase dramatically.

*Unless it turns out to be a thermal fuse, in which case you're screwed again.

Offhand, it plausibly looks like a Bourns polyfuse (or whatever name they use), I think.  Would guess the 4 is either the amperage, or a type code.

Tim