Hey there, so I am experiencing an issue that I am not too sure how it happened. Possibly due to a crash in lightly damp grass, but the quad flew fine after for many packs. The next morning, I am at my bench messing with the rates in Betaflight. I unplug it, and plug in a new pack. The FC booted up, flashed a couple leds, and then died. However, when I am plugged into USB, the FC is fine. Everything is detected in Betaflight and I can see it working and responding fine to input. There are no melted spots on the FC, no debris, nothing. I have inspected it x10 over even with magnification.

I have done some research, and it seems that possibly my 5v voltage regulator has died somehow. I read a little bit about using a 5v BEC to jump the power into a 5v pad on the FC. I currently have a few BEC's on the way to do just this. However I still have a few questions and some general weirdness I am curious to know about

So firstly, when I use a multimeter to test voltage - I see like ~3v coming out of a 5v pad. If the regulator was bad, wouldn't this be near 0v? Or is it possible some volts can make it through the regulator if it is fried? 

Secondly, last night while at my bench, I had the FC plugged into USB and I unplugged the RunCam Nano. After, I unplugged it from USB - I just so happened to decide to plug a battery in to see if it would boot up once more. Well it did much to my surprise. The FC was working as expected. I found this odd, so I unplugged the battery and plugged the RunCam back in thinking something happened and it works now. Nope. After plugging in the RunCam - the FC died. I then removed and plugged the battery back in, with the camera removed, saw the FC boot just fine like I discovered, and when I plugged the RunCam back in: the FC died. 

It seems that since the voltage regulator is no longer sending 5v (getting ~3v on a 5v pad), and when the RunCam tries to pull voltage - it kills the FC because there is not enough voltage to power everything. I dunno, just a theory. I am worried here though because I have an upgraded Caddx coming in for this Tinyhawk, and I don't want to plug it in if there is some weird short happening. I am a bit annoyed that this Tinyhawk has a proprietary board that costs $75 to replace. I am hoping I can repair it, otherwise I am just going to get a 20x20 adapter and build something from scratch for it. I love this size quad for where I live, so I would like to keep it around!

Sounds like u lost the 5v regulator.. I personally would NOT replace it with anther Emax AIO.  You have a bunch  of options.. I personally like the Darwin f4 1-3s aio.. granted it doesn’t have a rx or vtx.. but you can fly that little beast on 3s and it’s a BLAST!  
 If your upto the task you CAN reuse the emax 200mw vtx but I would suggest using an better antenna.  
 I recently killed my Darwin fc .. but it had been beat to hell and back.  You can source one locally or if ur not in a hurry I found them as cheap as $35 from Stonehobby.com (China)…
 At the moment I am having to design / 3d print new camera mounts and rear standoffs as the hd-zero nano camera WILL fit.. but not as well as I like..
 There are a bunch of 3d prints on thingiverse for whoop fc adapter plates for the th freestyle..
https://www.racedayquads.com/tools/forum...e-upgrades
Here is all the stuff my TH Freakstyle has endured ..