As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) NEARING FINAL APPROACH THE PILOT NOTICED HE HAD LOST PRIMARY AVIONICS POWER AND THE STANDBY POWER SUPPLY HAD ENGAGED TO PROVIDE BASIC POWER. AN UNEVENTFUL LANDING WAS CARRIED OUT. MAINTENANCE DETERMINED THE AVIONICS MASTER SWITCH (PUSH TO ENGAGE, PUSH AGAIN TO DISENGAGE) HAD DISENGAGED TO THE (OFF) POSITION BY ITSELF. THE INTERNAL LATCHING MECHANISM IS NOT VISIBLE FOR INSPECTION AND THE SWITCH IS IN THE PROCESS OF BEING REPLACED.