As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER TAKEOFF CAPT'S AIRSPEED BECAME UNRELIABLE. SWITCHING TO ALTERNATE ADC PRODUCED RELIABLE INDICATIONS. PERFORMED LT ADC BITE CHECK NO FAULTS SHOWN ON MDC. NO EXTERNAL FAULT SHOWN. PERFORMED ADC FUNCTIONAL TEST, ALL OK. AS PRECAUTION REPLACED LT ADC COMPUTER PER 34-12-01, ADC TEST OK. PERFORMED MDCP GROUND TEST 30, ALSO OK.