You went and done did it, you killed your Ubiquiti Airrouter, because you grabbed the wrong wall wart and overvoltaged it. And now it's dead.
Well, there's a good chance that only the little switching DC-DC 5V to 3,3V downconverter circuit blew up.
I removed the dead DC-DC converter chip and its associated inductor and diode, Did a test run with an external 3.3VDC power supply to see if the Airrouter was in fact repairable (that it still worked with this supply), and then used a linear voltage regulator to create the 3.3VDC the router circuits want. I used a regulator that was spec-ed to have low dropout voltage, as the input to output voltage difference isn't that much. And one that can do one and a quarter amps. I wanted to keep the input voltage at 5V, so if someone plugs a cell phone charger cable or such into the USB jack, it won't get blown up by excessive voltage. I mounted the regulator's heat sink atop the ethernet jacks. I used some sheet aluminum I salvaged from an old video monitor, though I probably made it bigger than it needed to be. In any event, the Airrouter was back on the air!
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Fixing the Airrouter you blew up with the wrong wall wart
Sat, 12/29/2018 - 18:01
#1
wa2ise
Fixing the Airrouter you blew up with the wrong wall wart
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I used a LM3940it 3,3v regulator. As that's what I had on hand, that could do the low drop out, from 5V to 3.3V. And it can take up to 12V input (at least mine did!) Bay Linear https://www.digchip.com/datasheets/parts/datasheet/064/LM3940-pdf.php says 26V, but TI and National Semi says theirs' only 7.5V, but be aware that this voltage will also appear on the USB port. If I did this again, I'd get the KA278R33 https://www.onsemi.com/pub/Collateral/KA278RA05C-D.pdf regulator, it can take up to 35V input. Or the LM1085 http://www.ti.com/lit/ds/symlink/lm1085.pdf 3A and max 27V in.
Denis