AN MD80 CREW RPTS PRESSURIZATION MALFUNCTION AT FL340; MANUAL CTL WAS GAINED AND THE FLT DIVERTED.

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CRUISING AT FL340 JUST E OF THE INTXN; WE RECEIVED A CABIN ALT WARNING. WE ACCOMPLISHED THE MEMORY ITEMS AND DECLARED AN EMER WITH ATC. I STARTED A DSCNT WHILE FO ACCOMPLISHED THE QRH PROC. ATC IMMEDIATELY CLRED US TO FL330 AND THEN TO FL240. FO GAINED CTL OF THE CABIN USING MANUAL PRESSURIZATION; THEREFORE; I EXPEDITED THE DSCNT TO FL240 BUT DID NOT CONDUCT AN EMER DSCNT. THE MAX ALT THE CABIN REACHED WAS 9800 FT. I COMMUNICATED WITH THE FLT ATTENDANTS AND THEN MADE A PA TO REASSURE THE PAX. I THEN CONSULTED WITH DISPATCH AND DETERMINED THAT ZZZ WAS NEAREST SUITABLE ARPT FOR A DIVERSION. WE CONTINUED AT FL240 USING MANUAL PRESSURIZATION TECHNIQUES AND LANDED WITHOUT FURTHER INCIDENT. AT ZZZ WE CHANGED ACFT AND PROCEEDED ON TO ZZZ1. AS BACKGND; THE ACFT HAD A HISTORY OF PRESSURIZATION CONTROLLER PROBS. THIS WAS OUR SECOND LEG WITH THE ACFT; THERE WERE NO PROBS ON THE FIRST LEG. 2 TIMES DURING CLBOUT FROM ZZZ2; THE 'XFER LOCKOUT' AND 'STANDBY ON' LIGHTS ILLUMINATED AND BOTH TIMES THE ABNORMAL PROC RETURNED THE SYS TO NORMAL. WE HAD JUST MADE LOGBOOK ENTRY ABOUT THIS PROB; AND WERE DISCUSSING MANUAL PRESSURIZATION ISSUES WHEN THE WARNING OCCURRED. I WOULD LIKE TO COMMAND THE FO FOR HIS EXPERT AND TIMELY HANDLING OF THE CHKLISTS AND COMS WITH ATC; AND ESPECIALLY FOR HIS EXECUTION OF THE MANUAL PRESSURIZATION PROCS. THE FLT ATTENDANTS DID A GREAT JOB WITH THE PAX. AS FAR AS I KNOW; WE FOLLOWED AND ACCOMPLISHED ALL PROCS APPROPRIATELY.