Low voltage coming out of Pixhawk


I’ve got a Pixhawk 2.4.8 that I’m trying to set up with a Spektrum AR631 receiver. I’ve got a PPM encoder set up between them, but the encoder and receiver don’t seem to be getting any power when the Pixhawk is powered. I measured the voltage coming out of the Pixhawk and it’s only 4.88 V. As a result, the voltage coming out of the PPM encoder is only 2.69 V, not enough to power the receiver.

If I power the PPM encoder with a separate 5V supply, it and the receiver light up, but there still doesn’t seem to be any signal going to the Pixhawk as the radio calibration in Mission Planner doesn’t show any response.

Any ideas? I would have thought the Pixhawk would output at least 5 V.