What was found
TO GET A NORMAL RADAR RETURN IN AUTO OR MANUAL, GAIN NEEDS TO BE IN THE MAX POSITION. GROUNDED - YES. MDS OMF INDICATES NO FAILURES. ACCOMPLISHED WEATHER RADAR OPERATIONAL TEST W/ NO FAILURES INDICATED. ACCOMPLISHED GPWS OPERATIONAL TEST OBSERVING CORRECT WINDSHEAR ANNUNCIATIONS. CONFIRMED WXR PANEL GAIN CHANGE OUT OF 12 O'CLOCK IS REFLECTED ON NAV DISPLAY. REF B737-9 AMM 34-41-00. ETOPS GROUND VERIFICATION SUCCESSFUL.