Update 04/27/2012 – Good news. It looks like there is no more need to cut the trace and solder in the resistor as demonstrated in this post unless you’re still running stock firmware.
The latest ER9X firmware has a an option call “Enable PPMSIM” in the Radio Setup screen. It allows you to turn it ON and the er9x firmware routes the PPM signal to the trainer port through a alternate path. Therefore, it bypasses the module and thus the need to add the resistor.
Original Post below…
Here’s my quick writeup on the trainer port resistor mod.
First, some helpful links to original articles on this. They contain a description of the problem and the solution.
- Original PDF on “Fixing the 9x PPM in problem”
- A more visual description of the issue and illustrated steps to fix.
- An updated version of the above with a video.
I prefer to use version 3.
The reason is because it has since been discovered that the problem only appear to affect the Turnigy 9x module. Others have noted that using an Assan module or FrSky module in the back doesn’t exhibit the issue.
Therefore, instead of modding the transmitter. We are going to apply the fix to only the Turnigy module. This is also simplier because you only have to unscrew two screws instead of the 6 screws + unfasten a wire harness to gain access to the Turnigy rear board.
Please follow the above video for a howto. It’s pretty simple and well done.
- Use a 1k resistor. (I chose to use SMD)
- Cut the trace with an xacto knife or file.
- Solder on the 1k ohm resistor. (surface mounted 102 resistor)