Using a 5vDC 2.5A adapter instead of a 12vDC 1A adapter... it seems to be working fine??

Thread Starter


Joined Sep 9, 2016
Hello all, I am new and I have what is a noob question I think... but I am puzzled and I was wondering if anyone can tell me why it's working.

I have a router, a linksys WRT54G. Its like 10 ten years old. It takes a 12vDC 1A power adapter. I had an adapter from a different router, a D-Link WBR-2310, also about 10 years old. The D-Link uses a 5vDC at 2.5A.

Now, my limited understanding of electronics is that voltage X amps = watts. So the Linksys adapter is 12 watts and the d-link adapter is 12.5 watts.

Does this explain why it seems to be working fine? The router isn't getting hot in the slightest, and i'm encountering no problems with the function whatsoever so far...
Anyway I'm confused as to why its working. I was hoping someone could shed some light on this question?
I realize it's kind of absurd to post a question about why something is working fine... I just thought its an interesting question.


Joined Mar 14, 2008
No, that doesn't explain why it works.

Apparently the 12V router is capable of working on 5V, which is unusual.
Perhaps the 12V router has a 5V regulator for the internal parts so it will still work on 5V.

But never try the opposite (applying 12V power to a 5V part).
That will likely result in letting out the magic smoke.

Thread Starter


Joined Sep 9, 2016
I remember I read in a few places that over-amping tends to be safe since the device will only pull as many amps as it needs.
However I wish I understood why the 5 volts is somehow working.
Thanks for letting me know this is odd though!


Joined May 23, 2013
It could well be that the 5 volt supply is actually giving out more than 5 volts. the clue is that the 5 volt psu is rated at 2.5A and may have a higher voltage at lower current. I tested some so called 5 volt Chinese psu's that off load read 10 volts and at full rated load were still giving 8 volts, which may explain why it seems to be working ok.
Some 12 Volt supplies were giving 18 volts off load and only 10 volts at full load.
These were the type that had a mains transformer and rectifier with no regulation. The switch mode ones are much better at giving the correct voltage.


Joined Nov 4, 2013
Typically routers have a small buck converter type power supply in them to make the 5 and or 3.3 volt rails for the digital circuits so any voltage over 5 volts and below the converters upper limit ~18 - 24 volts works just fine.