AC adapter confusion

I've mixed up my AC adapter for my router with several other AC adapters. The back of the router says "DC Input: 5V/2A", and I've found an AC adapter that says:

I/P AC 100-240V 50/60HZ 0.3A
O/P DC: DC 5V/2A
There's also a weird polarity symbol that I'm not sure is relevant.

I'm not sure if this is the original AC adapter that came with the router, but will this adapter safely power my router without burning it to a crisp? Thanks!

That's telling you it's taking 0.3 amps at 120 volts, and putting out 2 amps at 5 volts. (So it taking 36 watts input and putting out 10, which I think is probably miserably inefficient, but I haven't looked at any of my wall warts in a long time.)

The polarity symbol is very important; it tells you whether the tip or the ring is negative. The other end needs to expect the same polarity. If it doesn't, it won't work, and the unit may be damaged.

You've probably picked out the right adapter, but if you didn't, and can't find a polarity symbol on the router, you basically have a 50% chance that it will work beautifully, and a 50% chance you'll melt it.

edit: look through all your other adapters, and if none of the others are 5V/2A, that's almost certainly the right one. Also note that plug thicknesses come in many variants, so if it fits, that's also evidence that you've chosen the correct adapter.

Unfortunately the router doesn't specify whether the ring or tip is negative. I don't suppose anyone here has ASUS WL-520GU? It's a fairly common router for running DD-WRT or Tomato.

I did check my other AC adapters and most of them specify that the ring is negative and the tip is positive (some of them don't bother to print this information at all). Is negative polarity on the outer ring usually the case with AC adapters? If that's the case, then it seems like the 5V/2A adapter may be a safe bet even if it's not the original AC adapter. I'll go through my inventory of adapters again to be on the safe side.

It would be great if these things were standardized. My collection of adapters isn't this bad, but it's close:


Well, if you have other 5V/2A adapters that will physically plug into the router correctly, then unless they're all the same polarity, there's no way to know which one is correct. (if they're all the same, they should ALL work.) Maybe try contacting ASUS to ask them what brand the power supply would be?

Actually a better question would whether the router wants tip- or ring-positive. Power adapter brands can change during a router's run, but the specs on the router never should.

You could also check the manual; it should be available for download if you don't have the paper one anymore.

Ah, I've had this problem many times in the past. To the point that, these days, I'll take a white paint pen and write the name of the device on the adapter. Looks a little gaudy, maybe, but it sure is helpful.