AIRLINE MAINT POLICY - IMPROPER MAINT PERFORMED.

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A B-757; ARRIVED AT LAX WITH THE FOLLOWING ITEM IN THE LOGBOOK; 'R-HAND WING STROBE COMES ON WHEN RED ANTI- COLLISION LIGHTS ARE TURNED ON.' I FOUND THE UPPER BODY ANTI-COLLISION LIGHT LENS BROKEN; CAUSING A 'WHITE' FLASHING LIGHT INSTEAD OF THE NORMAL 'RED' COLOR. THE UPPER ANTI-COLLISION LIGHT LENS WAS NOT IN STOCK; SO THE XA00 MAINT CTL SUPVR HAD INSTRUCTED THE MECH TO REMOVE THE UPPER ANTI-COLLISION LIGHT LENS AND LIGHT ASSEMBLY PER CDL 33-08. THE MECH PROCEEDED TO REMOVE THE LENS AND LIGHT ASSEMBLY. AT THE END OF HIS SHIFT HE LEFT THE ITEM OPEN BECAUSE THE XA00 MECH DID NOT HAVE AN AIRWORTHINESS FOR THE B-757 ACFT. LATER A DAY SHIFT MECH CALLED MAINT CTL REQUESTING A PLACARD PER CDL 33-08 AND A PLACARD WAS GRANTED AND THE DAY SHIFT MECH WAS INSTRUCTED TO BE SURE THE ITEM WAS DEACTIVATED CORRECTLY AND THE ACFT WAS NOT DISPATCHED WITH 'HOLE' IN THE UPPER FUSELAGE. THE MECH PROCEEDED TO PLACARD THE ITEM; BUT DID NOT GET A CHANCE TO CHK THE PREVIOUS MECH'S WORK BEFORE THE ACT DEPARTED. THE ACFT DEPARTED LAX; BUT WHILE CLBING TO 19000 FT; THE ACFT COULD NOT PRESSURIZE ABOVE 5.4 PSI; AND THE ACFT RETURNED TO LAX. MAINT FOUND THAT THE UPPER ANTI- COLLISION LIGHT ASSEMBLY BASE HAD BEEN REMOVED INSTEAD OF JUST THE LIGHT ASSEMBLY. AN UPPER ANTI-COLLISION LIGHT LENS WAS PURCHASED IN LAX AND THE LENS AND LIGHT ASSEMBLY WERE REPLACED AND ACFT RETURNED TO SVC; WITH NO FURTHER PROBS. MY PERCEPTION OF WHY INCIDENT OCCURRED. 1) THERE IS NO WRITTEN DEACTIVATION PROC IN THE MAINT MANUAL OR CONFIGN DEV LIST ON HOW TO DEACTIVATE THE UPPER ANTI- COLLISION LIGHT ASSEMBLY. THERE IS A PICTORIAL ILLUSTRATION ON HOW TO DEACTIVATE THE LOWER ANTI- COLLISION LIGHT ASSEMBLY ON THE PREVIOUS PAGE OF CDL ORDER 33-07; BUT NO REF ON CDL 33-08. DEACTIVATION PICTORIAL ILLUSTRATION NEEDS TO BE ISSUED FOR CDL 33-08; BOEING 757 CONFIGN DEV LIST. 2) THE MECH THAT PLACARDED ITEM FAILED TO CHK THE PREVIOUS MECH'S WORK BEFORE SIGNING FOR THE WORK; AND REQUESTING TO PLACARD THE ITEM. 3) THE ORIGINAL MECH THAT PERFORMED THE DEACTIVATION OF UPPER ANTI-COLLISION LIGHT; REQUIRES TRAINING TO AVOID DISPATCHING AN ACFT IN A NON-AIRWORTHY CONDITION.