I have a clone Pixhawk which I have been using with two 3DR modules, one attached to a bluetooth module, which connects to my Android device.

After a year of working perfectly, the 3DR telemetry is not being transmitted any more, although my OSD is reading it OK on Telem Port 2. I've tried swapping the ports..no change.

I've tried installing different firmware too....no difference.

After many hours of head scratching I have removed the Pixhawk and re-installed my APM 2.6, and everything is back to normal, working perfectly.

Strangely I have discovered that when the Pixhawk is powered by a USB cable only, I can connect my Android device fine with Tower, as before.

If I power the thing with the power module, I cannot connect, although the two 3DR modules have solid green LEDs and the Android is connecting with the bluetooth module....?

Everything else on the FC setup seems to be fine, radio is calibrated, compass and battery sensor.....

All very odd and not a little irritating! 

Any ideas anyone?

Bes.t DP.