What was found
CABIN ALT EICAS AT FL370 QRC/QRH EXECUTED. RAPID DESCENT. FAULT IN AUTO 1 CONTRLR. AUTO 2 WORKED PER PILOT, AT FLIGHT ALTITUDE, AUTO CONTROLLER #1 HAD A COMPLETE FAILURE. FLAGGED FOR SDR ACCOMPLISHED BITE TEST OF BOTH 1 AND 2 AUTO PRESSURE CONTROLLERS REF FIM 21-30 TREE 802. NO FAULTS ON EITHER. OUTFLOW VALVE OPS ADD EMP:U094635 CHECK NORMALLY IN AUTO. REQUEST MEL 2131A DUE TO HISTORY OF #1 AUTO PRESSURE CONTROLLER. NIS DENVER. COMPLIED WITH MEL 2131A. OUTFLOW VALVE VERFIED TO OPS CHECK NORMALL IN MANUAL MODE. OK TO DEFER AUTO 1 CABIN PRESS CONTROL SYS CONTROLLER. REMOVED AND REPLACED AUTOMATIC PRESSURE CONTROLLER #1 REF 21-31-02. OPS CHECK, GOOD.