Taranis QX7 - Replacing MCU - No 3V3 alimentation

[Thibv]

Hello,

A friend of mine has got a trouble with his Taranis : after trying to flash a Rx with the Taranis (and maybe because of some mistakes), the Tx shuts down. He could turn back on, but some buttons didn't work anymore.
I've opened the Taranis to check HW. The buttons were OK, so I thank the MCU problems with some GPIO, and I've changed the MCU.

The soldering seems OK, but I cannot see the USB device on my computer. I re-opened it, and found that the 3V3 alimentation doesn't work.

- Do you have the schematic of the 3V3 circuit ? It seems to be a DC-DC. This part of the schematic would be a big help to debug the board.
- Do I need to externally flash the MCU for the alimentation (DC-DC ?) to be ON ?

Thank you,
Thibv.

[Thibv]

Hello,

Is there someone here who has already replacing the MCU on a Taranis ? Do I need to flash it externally, with SWD signals on the testpoints near the MCU ?

Thank you,
Thibv

[Kilrah]

No, just USB.

[Thibv]

I tried to solder the MCU and flash the bootloader a few months ago, without any success.
I've retried yesterday, and it's all good ! The Taranis is back alive. Indeed, only USB was necessary to flash the STM32. Here is the procedure, if someone else find this post :
- Change MCU, double check soldering
- Install Zadig
- Start your Taranis in bootloader mode. You'll probably need to keep the power button pressed, because alimnetation is not maintained yet by the MCU
- Install drivers with Zadig
- Open Companion, download the latest firmware
- Try flashing the Tx, it should work

Thank you for your help, and for this good forum. This post can be closed.
Thibv

[Kilrah]

Not necessary to "start Taranis in bootloader mode" nor to mess with the power button. DFU bootloader is running anytime the USB cable is plugged in with the radio off.

[Thibv]

No, i couldn't connect to the MCU without pressing the button. No device found by STM32 tool without it.

[Kilrah]

Then something else must be wrong, when connected while off the MCU is powered by the USB port. That part of the circuitry must be faulty.

[Thibv]

Possible, yes. Do you know where/if I can find the schematic of the Tx ? I probably have a problem with the speaker too.