APM 2.6 loses PPM signal between batteries

Hi Everyone!
First time poster, but long time lover of flight. I’ve used newer Pixhawks, but decided to try out an APM 2.6 due to the price point and rave reviews that users STILL give them. So far, I absolutely love it! It got my tricopter off the ground and running steadier than I’ve ever seen it.
The only peculiarity I’m hammering out is with the PPM. Signal:

  • I’m using a FrSky D4R-II receiver in PPM mode which is connected to input channel 1 on the APM.
  • I have the required jumpers in place on both the APM and the receiver to communicate in PPM mode; signal pins on channels 3 and 4 on the receiver and signal pins on channels 2 and 3 on the APM.
  • With this setup, I can take the craft out to a field and fly to my heart’s content.
  • However, after I swap the battery out, the APM stops receiving the PPM signal.
  • After powering everything down, reseating all of the receiver connections, the powering back up, I can restore connectivity and fly again.

Weird huh? I’m wondering if something could be shaking loose in flight or if there is some defect in the APM?

  • I verified that the receiver works properly with other models.

Additionally, I verified the following during one of these “outages”

  • I verified that the receiver is still connected to my transmitter and receiving power from the APM.
  • I verified that the transmitter can connect to other models reliably.
  • Mission Planner shows that the APM does not report any input from the receiver.
  • The APM’s inputs report the same values they would have if there were not receiver connected at all.

Has anyone ever seen anything like this? I know this is an older version of Arducopter, so is there a peculiarity with PPM signals?

Kind of a long post, but I wanted to be thorough. Thank you for your time!

Oops, I’m on Arducopter 3.2.1 and using a Taranis X9D.

Figured it out. I’m so annoyed with myself! One of the pins on the receiver was bent and the jumper for PPM mode wouldn’t stay on properly.

Corrected the pin. Reseated the jumper. Problem ceased. I had a great weekend flying my tricopter around. Finally had some nice weather!