As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THIS REPORT IS A SUPPLEMENT FROM 10 JUNE, 2011: THE PROP RPM INDICATION HAS FUNCTIONED NORMALLY SINCE THE INITIAL REPAIR OF THE ERRONIOUS INDICATION. THE PROP TACH GENERATOR WAS REPLACED WITH AN O/H PART. THE TIME SINCE NEW AND O/H ON THE FAILED PART IS UNKNOWN. NO PHYSICAL DAMAGE WAS VISIBLE TO THE REMOVED TACH GEN OR ITS DRIVE. SUSPECT THAT THE SIGNAL STRENGTH WAS AFFECTED BY UNKNOW INTERNAL MALFUNCTION.