As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING FLT 3177 CREW REPORTED RADIO DEAD SPOTS WHEN TRANSMITTING ON COMM NR 1 OR 2 FROM CAPT OR F/O'S SIDE. AIR RETURN TO MSP. MAINTENANCE REMOVED & REPLACED REU P/N ON/OFF 5170-1-9, S/N ON 223, S/N OFF 221. REU OPS CHECK GOOD IAW SF340 MM CHAPTER 23. ALSO REMOVED & REPLACED CAPT'S HEADSET. OPS CHECK GOOD IAW SF340 MM CH 23. P/N ON H10-30, P/N OFF H10-40.