What was found
(CAN) AFTER ADVANCING THE POWER LEVERS ON THE R/W THE NR 1 PEC CAUTION ILLUMINATED AND THE POWERPLANT MESSAGE ILLUMINATED. THE T/O WAS REJECTED. THE ACFT WAS RETURNED TO STAND. TASK 61& 8722,20 & 8722,06 & 8722,810 & 8722,818 -FAULT CODE 260. SERVO CURRENT DMD AND F/B DISAGREE & 8722, FAULT ISOLATION COMPLETED WITH NO FINDINGS. UNABLE TO REPRODUCE DEFECT. PILOTS LATER REPORTED THAT NR 1 PROP RPM WAS LOW COMPARED TO THE NR 2 PROP RPM. EMU REVIEWED AND IDENTIFIED THE 2 CHANNELS OF THE NR 1 BFT WERE REPORTING DIFFERING INFORMATION. BETA FEEDBACK TRANSDUCER REPLACED.