What was found
ON AFTER START RECALL "MACH TRIM FAIL" LIGHT ILLUMINATED, LIGHT EXTINGUISHED WHEN MASTER CAUTION RESET. GROUNDED - YES. T/S PER B737-900 FIM 22-13 TASK 817 AND 22-16 TASK 835. REVERSED CONFIGURATION CHANGES, REMOVED COLLARS AND RESET MACH TRIM AC+ DC C/B'S. "MACH TRIM FAIL" LIGHT DOES NOT ILLUMINATE ON RECALL. DFCS CURRENT FAULT TEST (DFCS BITE GRP #20) SHOWS NO FAULTS. PERFORMED DFCS BITE LIBRARY TEST #33 MACH TRIM FOR BOTH A+B PER B737-900 AMM 22-11-00-740-806 TEST PASSES. RAN TEST A TOTAL OF THREE TIMES, ALL THREE PASS. THIS CLEARS MEL 22-5C.