What was found
DURING CLIMB FROM FL 280 WE HEARD A SOUND, SO WE CHECKED CABIN ALT, THAT WAS NORMAL. THE NOISE WAS GETTING LOUDER AND CABIN ALT SLOWLY INCREASED. AFTER DESCENDING THROUGH FL 250 RECEIVED CABIN ALT CAUTION FOLLOWED BY WARNING MESSAGE. CABIN O2 MASKS AUTO DEPLOYED. F/A REPORTS ALL PASSENGERS WERE USING THE O2 MASKS. AT 10,000 FT REMOVED MASKS IN COCKPIT AND SMELT AN ELECTRICAL/RUBBER KIND OF SMELL. SMELL CONTINUED UNTIL AFTER LANDING. CREW AND F/A COULD TELL THE NOISE WAS COMING FROM THE SERVICE DOOR AREA. F/A REPORTED NO SMELL UNTIL AFTER LANDING AND THEN IT CLEARED ON ITS OWN AFTER ABOUT 2 MIN. SYNOPTIC PAGE SHOWED NORMAL INDICATION ON ESC AND ELCT PAGES. NO DAMAGE NOTED ON WALK AROUND. AIRCRAFT REMOVED FROM SERVICE, REF WO 300163 FOR R & R OF BOTH CABIN PRESSURE CONTROLLERS. R & R OF CABIN PRESSURE SELECTOR PANEL AND R & R SERVICE DOOR SEAL.