A B737-800 ACFT COCKPIT PEDESTAL HANDSET FOR P/A AND INTERPHONE USE WAS REPLACED WITH AN INCORRECT PART.

Narrative

A B737-800 ARRIVED AT APPROX XA19 HRS ON MAR/XA/07. THE ACFT HAD A CREW INBOUND RPT OF A LOUD SQUEAL FROM THE COCKPIT HANDSET. AN AMT WAS DISPATCHED FOR CORRECTIVE ACTION. HE AND/OR HIS LEAD AMT ORDERED A SVCABLE UNIT FROM STORES. AT AROUND XA40 HRS I WAS TOLD BY A LEAD AMT TO GO BY STORES AND GET THE HANDSET AND TO RELIEVE THE AMT AT SPECIFIED GATE. THE LEAD SAID STORES HAD ALREADY 'PULLED' THE PART. INDEED; I FOUND THE HANDSET ON A PICK-UP COUNTER IN THE FRONT OF THE STORES AREA AND PROCEEDED TO THE GATE. ONCE AT THE GATE I TOLD THE AMT TO GO AND FOUND THAT HE HAD ALREADY REMOVED THE OLD HANDSET. THE HANDSET HAS AN ELECTRICAL CONNECTOR SIMILAR TO A HOME PHONE LANDLINE. THE NEW HANDSET WAS PLUGGED IN AND THE CAPT AND I ACCOMPLISHED A CHKOUT OF THE UNIT. ALL OPS APPEARED NORMAL. I COMPLETED THE LOGBOOK CORRECTIVE ACTION BLOCK AND RELEASED THE ACFT. IN THE LINE ROOM LATER; I DISCOVERED THERE WERE NO LEGIBLE NUMBERS ON THE OLD UNIT. FOR SERIAL NUMBER 'OFF' I HAD TO WRITE 'UNK' FOR UNKNOWN. NOT HAVING A GOOD NUMBER OFF THE OLD UNIT WAS A CONTRIBUTING FACTOR. THE SHIFT CHANGE ALSO ADDED TO THE EQUATION. TO THIS DAY I DON'T KNOW HOW THEY ARRIVED AT THE PART NUMBER I PICKED UP IN STORES. I TRUSTED IT TO BE CORRECT; AND OBVIOUSLY IT WASN'T. QUALITY ASSURANCE FOUND THE EFFECTIVITY ISSUE AND HAD THE HANDSET AGAIN REPLACED WITH THE CORRECT PART NUMBER. THERE WERE; TO MY KNOWLEDGE; NO PIREPS OF THIS SYS IN THE 4 DAYS IT FLEW ON THE ACFT.