I love Ubiquiti products... however I absolutely hate their power supplies (PSU) and adapters. So many times I've had issues with them, especially when it becomes summer and today was a hot day... And of course, the PSU gave out!
How to diagnose? Well, usually the USG or similar Ubiquiti device starts to chirp like a bird, sometimes with just the console lights flickering as well... and if you have a GP-F120-100
with status light, you will notice that when you attach the USG to it, it starts to blink instead of a nice green steady status light. If this is you, you are in luck and can continue reading.
The other error might be your USB memory onboard that is bricked. I will not cover that situation.
However, most don't know what this error code means and simply buy a new router. So lets help you guys out and remember, that the PSU is actually outside the router, not inside the router and if you are lucky, all you need to do is replace the powersupply.
The USG 3P requires 12VDC or 12Volt and 1Amp to function correctly. If you have a spare 12V 1A or similar 1.2A... but 12Volt powersupply lying around, go try and see if it stops this chirping sound. Miles may vary, but out of the 100+ cases I have troubleshooted, most of the time, grabbing a PSU with a stable-ish 12V and 1A-1.5A output, does the trick!
Now, a word of caution, I always advice you to buy original products and get it replaced with the correct Ampere prescribed etc. and in the case of the USG-3P it is 12VDC (12V 1Amp) as indicated on the device itself. I recommend to RMA the existing PSU to Ubiquiti and obtain a new original one, even though its a cheap Chinese thing, but at the very least, its a cheap "made-to-fit-stamped-ubiquiti"-one