I have an issue with my ESC and/or FC on a quad I'm building. I'm currently not quite sure where the issue is but before I start checking all the solder joints I'd like some input.

Ive had the quad on but not armed on my bench (props off of coarse). A few times I have heard that melody that you get when you power up the quad although it already was powered up. I didn't see any glitch in the goggles (VTX is original Air Unit) that time it happened while I was looking. It also happened once when I was in Betaflight configurator as I was testing the motors. I didn't notice any glitch in motor RPM or anything.

What exactly is that melody? Is it the ESC rebooting or does it do that when FC initiates connection? I don't see or hear any glitches and the quad appears to keep functioning, no drop of video or glitch in motor RPM on test bench. If it wasn't for that melody playing I wouldn't think there was anything wrong at all. Should I be checking anything other than solder joints?

The startup melody is played when the ESC boots, and I believe the final two tones when it receives signal from the FC. If you are testing with low voltage (like a run down lipo at the lowest cell count) that may prevent ESCs from booting up or cause rebooting. But if you were running proper voltage, then that should not happen. It is even more odd, if you were testing (assume all 4 motors) in BF configurator and when it rebooted, your motors did not stop or glitch. The ESC uses the motors to generate those tones, so not sure how that is possible while they are spinning. Maybe you have accidentally connected a spare ESC and that is powering up in the background?! 

As mentioned, that is caused by one or more of the ESCs rebooting. That shouldn't happen if the ESC is being fed with a constant voltage in the required range for the ESC board that isn't going via a smoke stopper or a current limiting device, so you need to try to get to the bottom of that because it if happens mid-flight your quad will just drop out of the sky.

(27-Jul-2023, 02:09 AM)mstc Wrote: so not sure how that is possible while they are spinning. Maybe you have accidentally connected a spare ESC and that is powering up in the background?! 

I wasn't testing all of the motors at the same time

I was running at full voltage. I'll go through the solder joints again and check connectors. If that doesn't resolve the issue I'll have to go ahead an replace it.

Something was up with the ESC. I moved the electronics off the frame and tested, I could see very tiny sparks and very faint smoke. My desktop power supply was current limited and displayed current drawn was only about 20mA. I would never have thought there could be any sparks or smoke at 14V and 20mA. Just goes to show how little I know about electronics.

Assume this is a 4-in-1 ESC? Maybe some carbon dust or other conductive crap on the board? Worth to try a good alcohol cleaning (getting the ESC MCU pins) and testing it one more time if it hasn't burned out.

Yes, it's a 4 in 1 ESC. I put a new one in as I just want this quad in the air but I'll give a go at cleaning it properly and bench test it.