What was found
(CAN) WE NOTICED THE GEAR RELAY CB HAD POPPED. AFTER IT RESET ON THE GROUND. AFTER T/O, WE SELECTED THE GEAR UP BUT THE CB POPPED AND THE GEAR REMAINED DOWN. WE REQUESTED A RETURN TO THE AIRPORT. WE HAD 3 GREEN LIGHTS, COULD SEE THE GEAR DOWN SO DID NOT DECLARE AN EMERGENCY. LANDED SAFELY AND HAD MAINTENANCE TAKE A LOOK AT THE GEAR. THEY FOUND A DIODE WHICH HAD FAILED/SHORTED. THERE HAD BEEN HEAVY RAIN FOR A FEW DAYS PRIOR TO THE FLIGHT. OUTSIDE AMO FOUND SHORTED TRANSORB ASSEMBLY, DIODE, A227CR123, PN 100-361045-1 ON LANDING GEAR POWER RELAY K101. POSSIBLE SHORT DUE TO MOISTURE.