AFTER CHANGING AN UPPER DECK SLIDE ON A B747-400 FOR AN INTERNATIONAL CARRIER; MECHANIC PULLED THE DOOR HANDLE TO OPEN; REALIZING THE SLIDE HAD PARTIALLY DEPLOYED; BUT DID NOT INFLATE.

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I WAS PREVIOUSLY ASSIGNED TO FOREIGN AIRLINES; BUT I WAS ASKED BY MY LEAD TO DO THE JOB BECAUSE OF MY EXPERIENCE AND QUALIFICATION ON THE DOOR SYS. THERE WERE CHAIN OF EVENTS THAT LED TO THIS INCIDENT. BUT THERE WAS ALSO A GAP OF ROUGHLY 1 HR WAITING FOR THE SERVICEABLE SLIDE FOR FLT X TO ARRIVE. THAT NARROWED DOWN MY TIME TO GO TO MY PRE-ASSIGNED JOB TO FOREIGN AIRLINES. TIME WAS A FACTOR IN GETTING THE JOB DONE FOR ZZZZ FLT. REMOVED AND INSTALLED UPPER DECK SLIDE PER MAINT MANUAL. AFTER INSTALLATION; REQUESTED INSPECTION BUY-BACK. SHOWN THE INSPECTOR THE MODE SELECTOR WORKING PROPERLY. AFTER OPS CHK OF THE SELECTOR HAND WAS DONE; THE INSPECTOR WAS SATISFIED. WE VERIFIED THE BATTERY SWITCH IS IN NORMAL CONDITION (GREEN LIGHT). I TURNED MY ATTN TO OPEN THE DOOR TO INFORM MY PARTNER THAT THE INSPECTION PASSED. AS I PULLED THE DOOR HANDLE TO OPEN; I REALIZED THAT THE SLIDE HAD PARTIALLY DEPLOYED; BUT DID NOT INFLATE THE SLIDE. I BELIEVE THIS TYPE OF WORK NOT TO BE DONE ON THE GATE WHEN THE ACFT HAS SUCH A TIGHT SCHEDULE UNDER ANY CIRCUMSTANCES.