Everything blew up

Hey guys! Sad post here, so I’ve been heavily been working on my board to get it working before school gets out (tomorrow) I had finished everything and all I was doing was troubleshooting my Firefly remote system because it wasn’t binding so I pulled out my laptop set it next to the board and then I must have moved something? And a big spark came out of my loop key while it was already in. That scared the sh*t out of me so I unplugged everything and started to look through everything, one of the receiver wires got disconnected at the solder join, and there was black sut on the uart ground pin area of the foc box. Now the receiver screen won’t turn on even when I plug it in to my laptop and I can’t connect with the focbox, there’s not even a light when the power is connected although it is outputting power on other pins in the uart other than the 3.3v


You really need to cover the exposed connections on that loopkey


Your pictures did not upload

I was planning on it but I don’t believe that was the problem, is there a way to trouble shoot the motor controller?

Try refreshing it

What esc are you using?

Looks like a focbox

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Yeah I’m using a focbox

What is this connected to
Send an image

My receiver

I believe I have found the issue with closer inspection I’ve found sut on the receiver’s antenna

and during the receiver troubleshooting I had pulled it out to see if it would get better reception and when I moved around a bit the base of the antenna made contact with the positive loop key and created a surge through the receiver up through the ground wire (had been unsoldered and the clear heatshrink was black with sut) and into the board where the final amount of sut has been found. So my question is is the focbox recoverable? @JohnnyMeduse


I had something like this happen to me.
It fried my STM32 Microcontroller… Hope you have more luck.

Seems like you had a high current/voltage short to your 3.3V rail - which is used for the microcontroller :frowning:

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If you have a multimeter check if you have a short circuit from
GND to 3.3V

GND to 5V

Worst case would be that your Battery Voltage directly short circuited to the 3.3V rail - which will toast your STM32 and depending on which rail was shorted as well it might also affect the DRV (and of course the receiver will also be toasted).

The DRV creates the voltages needed for the STM32 so please make above checks with the multimeter and also provide the voltage that you read from GND to 3.3V and GND to 5V to be sure.


They aren’t shorted, the 5v pin is giving me 5v and the 3.3v pin is giving me 0.4v…

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then you might only have a broken DRV if you are lucky - but STM32 don’t handle all that action very well… so I guess I would send it to someone to replace STM32 and DRV for you (if you can’t do it yourself).


check the TC2117-3.3VDBTR Voltage regulator first.

It’s always hard to say what is broken when you send in high current from 40V+ into a lowvoltage circuit

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I did similar to you a few years back, shorted the VESC USB carcass to Vcc, in my initial analysis this killed the DRV, STM and the voltage regulator, with a high chance of some passives getting destroyed, plus killing the arduino and NRF module I used as radio

Never got around fixing since I don’t have the tools, but if the PCB itself isn’t damage it can be repaired

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my bet is STM32F / DRV / and 3.3V VREG broken.
Depending on how much current went in for how long maybe also some capacitors to take care of.
Not an easy repair


Parts will set you back around

STM32F405 - 12 $
DRV8302 - 7 $
TC2117 - 1 $
other components (caps, …) - 2 $

You will need a reflow hot air station and good solder/flux.
You have to monitor the temperature and it’s quite tricky to solder the STM32 without bridging and to solder the bottom GND pin of the DRV8302.

Best is really to send it to someone who did it a couple of times imho.


Plus a way to flash the bootloader if there is no other vesc available