What was found
CRUISE ALT 370 -DISCRETE CABIN ALT LIGHT ILLUM AND ASSOCIATED EICAS MSG CBN ALT APPEARED. CABIN ALT REACHED 11500 AND SLOWLY INCREASING BY TIME WE WERE EMERG DESCENDING. CABIN REMAINED ABOVE 10000 DURING DESCENT UNTIL APPROX 140 MSL. AFTER LEVELING AT 100 MSL CABIN ALT CONTINUED TO DESCEND TO LOW THOUSANDS 1000-2000 FT. THIS OCCURRED WHILE IN AUTO 1 ON CABIN PRESS PANEL. BITE CHECKED NR 1 AND NR 2 AUTOPRESS CONTROLLERS, NOFAULTS. REPLACED NR 1 AUTO PRESS. CONTROLLER AND SEL PNL PER M/M. REPLACED NR 1 PRESS. CONTROLLER C/B. PRESS A/C CKS OK. CKED IXT