What was found
UPON ENG START UP FOR DEPARTURE, PILOT NOTED LT DIGITAL TURBINE INDICATOR SHOWED NO DIGITS. ENG STARTED NORMALLY & ALL OTHER INSTRUMENTS READ NORMAL & THERE WERE NO ENG COMPUTER FAULTS. A SPECIAL FLIGHT PERMIT WAS ISSUED & ACFT WAS FLOWN TO HOME BASE WHERE IT WAS DETERMINED THAT THE INDICATOR WAS FAULTY. AN OVERHAULED INDICATOR WAS INSTALLED & THE ACFT RETURNED TO SERVICE. THE FAILED INDICATOR HAD 1.1 HRS SINCE OVERHAUL & A RECORDS CHECK SHOWED IT HAD BEEN REPAIRED FOR THE SAME DISCREPANCY.