Flytower Mini F4 flight controller dead

As I mentioned in aritcle before, I start to assembly my new cine-whoop drone – Reptile CLOUD-149 RC Drone with Flytower F4 Mini Flight controller (BTW really cheap but good FC).

Yes Yes – I need to make it better than before, so tried to connect Smartaudio from VTX (Mini VTX5848) to FC (as I found later there’s no Smartaudio but IRC Tramp which works fine connected to TX1 on FC with no receiver connected).

What I did to kill the FC?
During changing resources on FC and trying to use existing pads, (As there’s only UART which is already used for receiver) I plug cable from FC (with LiPo already connected to ) to VTX socket together. LEDs on FC just stop lights and there was not possible to connect to Betaflight anymore (even no error if I put USB to PC) and FC seems totally dead. (later I found that I kill also RXD output on VTX)

Finding root cause:
I tried to measure voltages on PCB and I found out that 5V regulator works OK, but 3,3V regulator output was jumping between 0-1V (short circuit protection active). Also I tried to measure resistance on 3,3V regulator output and ground – there was short circuit.

First i try to unsolder regulator, but PCB was still shorted, so STM32F405 goes out as well.
put regulator back to PCB and viola, green LED is back (and STM32F405 dead).

How to repair?
Luckily I had some old Omnibus F4 V3 clone from my very first build with dead regulators.
So easily remove F405 chip with heat-gun from Ominibus and solder it back to F4 Mini.

Now blue led is blinking as well 🙂

Just go to betaflight and flash latest (4.1.1 ) OMNIBUSF4 (as F4 mini target)

works perfect ! (almost – see PS)

PS: after replacing F405 I found out that gyro was dead, so I replaced gyro form Omnibus F4 as well, but still dead 🙁

So ordered new FC – F4 Noxe V1… later I found out (with magnifier) that my soldering was not perfect and one pin of F405 floating. So resolder and giro works perfect:)

BTW for remowing parts from PCB (also BGA) I’m using Bosch GHG 660 heatgun with this settings:

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