Drone went for a swim, NEED help is my ESC or motors broken?

[leggyc]

Hi very new to fpv so need a little help

Basically, let a mate fly my drone (rookie mistake) he lost control, I lost sight of it and he crashed it straight into a puddle and was in there, fully submerged, for about 10 mins before we found it. I’ve seen forums online saying it should be fine if its thoroughly dried which I have now done extensively with a hair dryer and used compressed air to blow anything out of the motors. The drone turns on, I have video and connects to the controller. However, I can arm the drone (so it beeps when I put the stick in the arm position) but the motors do not spin at all. I’m not sure if there is something wrong with the ESC or all the motors and I am not sure how I go about identifying which is the problem. Currently don't have hold of a multimeter but will do in a couple weeks and only have access to betaflight. I have taken it completely apart to see if I could notice anything visibly wrong with the ESC but am non the wiser but in the process managed to disconnect a tiny wire (good job me) to the speaker so can no longer hear it beep. The drone is an Eachine wizard x220s with completely stock parts (not sure if that helps).

Cheers for any help

 

[wafflejock]

I'd put my money on burnt ESC.

The esc is basically a bunch of MOSFETs which are like gates for current flow that are controlled by a voltage change (as opposed to "regular" transistors which are like gates/switches that are controlled by a current and can effectively amplify a signal/changing current). The battery power goes through the MOSFETs into the windings on the motor, the only way you cook a motor is if the battery current gets shorted or otherwise too much power is pushed through the coils on the motor and they can't dissipate the heat quickly enough, eventually the enamel coating melts off and shorting will happen across the wrapped coils on the wire which will allow a lot of current to flow which will cause the motor to "cook" or burn off a bunch of enamel and some copper until the connection is broken (effectively the motor has become a fuse).

Chances are way higher I think that a short happened between the GND and + of the MOSFET output and put too much current through the MOSFET (in my experience this can happen just from stalling a motor/prop and giving it too much throttle). The motors are generally fairly water proof and need to have a whole lot of current pushed through them to cook (it happens, but more likely to knock a magnet loose and/or bend the rotor/bell on the outside of bldc motor than to cook them).

 

[wafflejock]

Also you shouldn't expect to hear startup tones if either the ESCs or motors are burnt but again very unlikely to toast 4 motors at once but very likely to just toast 1 ESC from moisture or other stress. The tones actually come from the ESC twitching the motors at high frequency no speaker on most of them unless have an extra "buzzer" piezo speaker for screaming when it's lost or out of power etc.

 

[leggyc]

Yeah the noise is coming from the buzzer saying when its armed and disarmed but no twitching of the motors on start up like it normally does when the battery is plugged in