As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
STANDBY INSTRUMENT WENT COMPLETLY DARK SUDDENLY DURING CRUISE. RETURNED TO FIELD, LANDING UNEVENTFUL. REMOVED ISI IAW AMM 34-12-16-000-801 CLEANED STANDBY PITOT AND STATIC LINES, IAW AMM 34-11-00-170-801 INSTALLED NEW IAW AMM 32-12-16-400-801 OPS CHECK GOOD. RETURNED TO SERVICE.