As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ABNORMAL VIBRATION DURING CLIMBOUT WITH CONDITION LEVERS AT 850 RPM. VIBRATION LESSONED AT 900 & 1020 RPM BUT RETURNED AT 850 RPM AGAIN. RETURNED TO FIELD. LANDING UNEVENTFUL. PERFORMED BALANCE ON NR 1 & NR 2 PROPELLERS, PERFORMED 6 BLADE RETORQUE ON NR 1 PROP IAW MAINTENANCE 6611002.