What was found
EN ROUTE TO PLN ON FLIGHT 2765, ATC REPORTED NO TRANSPONDER/MODE C READOUT ON NR 1 & 2 TRANSPONDERS. AIR RETURN TO DTW. MAINTENANCE CYCLED POWER, 1 & 2 TRANSPONDERS. OPS CHECK GOOD IAW SAAB MM CH 34, ALT REPORTING SYSTEM TESTED IAW FAR 43 APPX E PARA C.