So, I needed to flash and program my OSD so I disassembled the top plate, removed the OSD, flashed it, configured it, etc.
While I had it out, I decided to mod the RX/TX wires to include a jumper switch, so I could "turn off" the OSD (actually just make it not use UART1). By removing the jumper, I could communicate with the FC using BetaFlight.
I reassembled, used smoke stopper to make sure I didn't introduce any new shorts. I had my receiver bound, and checked the receiver tab for appropriate movement of all channels (all OK). I removed smoke stopper and plugged in battery directly to test the OSD both "on" and "off" - it worked great!
So on to esc calibration and motor testing. I unplugged the battery, removed the jumper, connected to Betaflight, did the calibration, and began testing the motors (had to do this without smoke stopper).
Everything seemed to be working fine - ran up each motor individually using the sliders in the motors tab (rotations OK). Then I used the Master to run up all 4 motors at the same time. Everything still appeared to work OK. I decided to take the Master slider to near full throttle. Damn! - Smoke on #1!
The smoke appeared to come out of the motor first, but this photo shows the damage to the ESC, so I'm not sure. I was too disappointed to disassemble for diagnosis yet, but I've already ordered 2 more motors and 2 more escs. So I have a week to 10 days for diagnosis... Not sure I'll be able to tell for certain, but I suspect I should have protected my motor wires better on the wrap around solder job I did. I did check screw length, and like I said, it worked for awhile.
Tip of the day: Buy 5 or 6 motors and 5 or 6 esc's for every build