What was found
ON FINAL FULL CONFIGURATION (GEAR AND FLAPS 40), THERE WAS NO INDICATION OF BRAKE RELEASE (RELEASE BARS NOT IN VIEW). EXECUTED A GO AROUND TO TROUBLESHOOT. RELEASE BARS CAME BACK FOR NO APPARENT REASON, WENT OFF AGAIN, BUT ALL INDICATIONS NORMAL AT 500 FT, LANDING UNEVENTFUL. REPLACED PROX DETECTOR PROCESSING UNIT IAW MM 32-31-71-4. OPS CHECK GOOD, PERFORMED NORMAL BRAKING TEST AND IN FLIGHT BRAKING TEST IAW MM32-42-00-5 NO FAULTS NOTED. ACFT OK FOR SERVICE. ACFT OK FOR SERVICE.