What was found
ON FLIGHT 3830 DURING CRUISE CREW REPORTED, LOST VARIOUS INSTRUMENTS AND BOTH TRANSPONDERS. ADVISED ATC THEY WERE RVSM UNABLE AND STOPPED CLIMB AT FL260. CONTACTED MAINTENANCE AND COULD NOT RESOLVE PROBLEM. AFTER ABOUT 20 MINUTES DISCOVERED AVIONICS MASTER NR 1 HAD RELEASED HALF WAY OUT WITH NO INDICATION SUCH AS THE SWITCH ILLUMINATING. RESETTING THE SWITCH RESTORED ALL INSTRUMENTS. AIRCRART REMOVED FROM SERVICE. CLEANED SWITCH AND OPS CHECKED GOOD. AIRCRAFT RETURNED TO SERVICE.