As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING NORMAL PREFLIGHT INSPECTION, IT WAS DISCOVERED WE HAD A NR 1 BUS TIE CAUTION LIGHT. THE ACFT WAS NEVER FLOWN ON THAT DATE. UPON FURTHER INSPECTION OF THE MASTER ELEC BOX, WE FOUND THE BOX WAS CLICKING CONSTANTLY WHENEVER POWER WAS APPLIED & WE SMELLED AN ELEC BURN EMITTING FROM THE BOX ITSELF. THE NR NR 1 MASTER ELEC BOX WAS REPLACED & THE ACFT WAS RETURNED TO SERVICE.