Also posted on Forum.

Hi All,

I have an APM 2.5 board (brand new), it's my second APM, I have another 2.5 in an aircraft, this one is for a quadcopter.

I've loaded up 2.9 through mission planner, all good.  Then power cycled the APM and checked everything is fine, I can connect just fine and get telemetry through 3DR radio and/or USB.

HOWEVER, when I connect my RC receiver up, it works ok and powers up, all good.  But as soon as I turn my RC transmitter on the APM hangs, crashes or whatever you want to call it.

I can be connected via Mission Planner and receiving telemetry fine, then when I turn my Tx on everything stops.  The orange lights at the front of the APM flash rapidly and the ABC lights either go out, or display a solid Orange.  I've tried all different combinations of power up cycles to get around the problem and nothing seems to alleviate it.

I have a 3DR power module powering the RX, APM and GPS, I do NOT have JP1 connected as per instructions, and the output stage only has the BEC's from the speed controllers on it along with a roll servo for my GoPro mount.

I've tried;

- Powering the whole thing from a seperate power source and removing the 3DR PM source

- Powering up the RX, turning the TX on and then powering up the APM

- Powering up the TX, then the electronics

- Powering up the TX, then the RX, then the electronics

I've also tried a completely different radio system, including a different transmitter and receiver.  When I use these, the APM doesn't even boot up, regardless of whether the transmitter is on or not.  The whole thing just goes lights out including the GPS.  Which is different behaviour to the original radio gear.

Basically I think I've tried all sorts of combinations and permutations to get this thing working.

All that being said, I've actually had it going once, and was able to calibrate the radio, and program everything up and fly the quad.  However, after I changed the battery over, it went back to this.

Reading through the forums I found "similar" issues, but nothing that seemed to describe exactly this scenario.  I have tried flashing and reflashing the firmware, and also got it going once by flashing another firmware (ArduRover) and then flashing the ArduCopter again and it seemed to work but I've not been able to repeat that.

I would welcome any ideas, or similar experiences, I think I may have to return the APM perhaps?

Many thanks

Biggles.