Hi all, i was rebuilding my 3"tadpole with hakrc aio. soldered the motors then plug in the battery got all the startup beeps. then i went to solder all the rest (rx, vtx). plug in battery then lost the last two beeps, and all the lights on the fc.Also no respond/lights when plugged via usb, rx still lights up.
I remember having a similar problem before and had to jump a 5v pad to another 5v. Does it sound like a 5v regulator problem this time? can i jump the 5v again?

If you're not getting any LED activity on the board with either a LiPo or the USB cable plugged in then you've likely either fried the 3.3V regulator which supplies voltage to the MCU, or you've fried the MCU itself.

Use a multimeter to measure what voltage you are getting from the 3V pad on the FC with a USB cable plugged in. If you are still seeing 3.3V on that pad, put your finger on top of the MCU chip to see if it is getting abnormally hot.