Monday, June 24, 2019

How to fix PMU Problems with X9-Lite (External Module not powered)

Here is a fix for the problem. With this solution you only bypass the useless PMU introduced by Frsky that is not working at all. The PMU is an unknown MCU. The surface is scratched so is not recognizable.

This method just connect the MCU STM32 PIN PA8 to the mosfet that provide VMAIN, that is the power supply to the external module. With only a short cable it is fixed. I couldnt test it a lot, but for now it is working fine.

I am glad if it fix the Problem for you.

Best regards,


  1. Thank you very much sir! You saved my radio!

    1. Hello Ben west,

      you´re welcome. I am glad that it worked with your transmitter.

      Best regards,

  2. Antes de nada muchas gracias, hasta ahora la única solución que he encontrado a ese problema, y he dado unas cuantas vueltas. A estas alturas tengo 2 dudas que a lo mejor me puedes resolver: me da un poco de miedo meterme a soldar ahí ¿no te has enterado de ninguna solución por software? el post es de julio de 2019, casi un año. Y otra, ¿te funcionaría el módulo r9m con el cable soldado?

  3. Hi, is this possible with the xlite pro?

  4. Glad I found this as it did fixed a problem with a new x9 lite. I've had x9 lites before but external modules are working just fine so it was a big surprise when this current one I have could not power external modules. Thanks so much for sharing this!