I believe I have a dead FC, but wanted to run by my approach & findings with all of you to see if you have anything else to add.
Starts off when I was attempting to install a Hellgate Buzzer onto an SPF3 FC. Things didn't go very well, and long story short, it ends with the quad not working anymore and the Hellgate Buzzer beeping loudly non-stop...
I pulled out the multimeter and began to dig deeper. With the battery plugged in, I could initially see that the FC and Receiver were not getting any power. The PDB, 4in1 ESC, & VTX all received power.
I began checking out the FC more and found that nothing was being outputted from the (+) pads. So since the receiver gets power from the FC, it makes sense that is off now too.
But here is the kicker.. When plugged in w/ micro-usb to cleanflight, the signal wires output (1V) to the ESC's, which allow you to control the motors through Cleanflight. Still no power to the Receiver, so no remote use.
So my conclusion would be that the power system onboard the FC is fried. I can see that the FC outputs signal, but not the 5V required to power itself or the Receiver.
Does anyone have any additional thoughts on this? Im curious to see if its safe to say this FC is done.
Funny, because I ordered a Omnibus F4 to replace it. Figured it would make for a quick replacement. Ill keep the SPF3 as a novelty for now and maybe use it for a spare build later on and rely on the PDB pads like you said.