SpeedyBee SB-F4V3 power issues

[Shraddha]

Hello,

I am working with a SpeedyBee F405 V3 flight controller. After plugging it into my PC and updating the firmware, I soldered on my RX, VTX, and camera. I then set up all the basic settings using Betaflight. After that, I mounted the flight controller on my stack and connected it to my ESC with the included cable.
When I plugged in the battery, I heard three beeps (indicating the ESC is fine) followed by two beeps (indicating the flight controller is communicating). However, the only LED that lights up is the red power LED, which is dimmer than usual. The RX and VTX have no power.
When I connect the flight controller to my PC, both the red and blue LEDs are bright, and the RX powers up, but the VTX still has no power. In Betaflight, when I go to the Motors tab, I can't spin up any of the motors.

Using a multimeter, I tested the following:

5V pads: got a reading of -0.3V
BAT pad: got a reading of -0.5V
Checked diodes: all were healthy
Checked resistance between 3V3 and GND: got a reading of 1.2 ohms
Checked for continuity between nearby solder joints: found no shorts

Any help would be appreciated.

[chandansanu]

For the motor part , recently bought a f7v3 stack, my motor didn't run till I enable bidirectional esc in beta flight app. Please check whether in beta flight 4.5 whether bidirectional esc is enabled in motor tab.

[ayush soni]

Shraddha
Hello,
as per your issue shraddha its seems like the 5v bec on your fc is dead or damaged
..and when u plug it to pc the vtx and rx get their power from the usb itself..
and for motoras always program your fc with esc connected and u can do one thing flash your fc and again progrma with esc connected