REPAIR OF SINCLAIR TECHNOLOGIES INC. DUPLEXER MODEL MR356B REPAIR OF SINCLAIR TECHNOLOGIES INC. DUPLEXER MODEL MR356B*2 S/N- CCV9693 FREQ. 443.65 MHZ - 448.65 MHZ BROWN BAY REPEATER JAN. 22/08

SCHEMATIC

RESOLDERED ALL CONNECTIONS INSIDE VIEW HAIRLINE CRACKS RESOLDERED ALL CONNECTIONS

ANTENNA I/P LINE CRACKED

ANTENNA I/P HAIRLINE CRACK (x 10 MAGNIFICATION)

2ND FILTER HAIR LINE CRACK

TOP VIEW WEAK MECHANICAL SUPPORT NO STANDOFF SUPPORT DAMAGED SLUG

ACTIONS TAKEN ALL CONNECTIONS TO CENTRE CONDUCTORS OF SEMI-RIGID LINES THAT WHERE VISIBLE WERE RE- SOLDERED. INSPECTED ALL CONNECTIONS AFTER CLEANING WITH IPA SOLVENT AND BRISTLE BRUSH. ANTENNA I/P CONNECTOR RE-SOLDERED AT JUNCTION OF CONNECTOR SHELL AND SEMI-RIGID LINE USING 'HOT PLATE' PROCESS. NEW SPLIT AND STAR WASHERS ADDED TO FRONT COVER PLATE ONLY. ALL REMAINING HARDWARE ON BACK PANEL TIGHTENED PRIOR TO TESTING. VSWR TEST CONDUCTED ON HIGH PASS (448.65 MHZ) AND LOW PASS (443.65 MHZ) WITH 50 OHM LOAD ON ANTENNA PORT.

TEST RESULTS AFTER REPAIRS VSWR TESTS AT 443.65 MHZ WITH 50 OHM LOAD ON ANTENNA AND XMTR ON LOW PASS I/P: <1.2:1. VSWR TESTS AT 448.650 MHZ WITH 50 OHM LOAD ON ANTENNA AND XMTR ON HIGH PASS I/P <1.7:1.

CONCLUSION: PROBABLE CAUSE OF FAILURE FATIGUED SOLDER JOINTS DUE TO STRESS ON EXTERIOR SEMI-RIGID LINES. ALL CENTRE CONDUCTOR CONNECTIONS ON SEMI- RIGID LINES WHERE NOT PRE-TINNED PRIOR TO BEING SOLDERED AT MANUFACTURER, LEADS WERE SOLDERED UNDER STRESS AS EVIDENT FROM LEADS MOVING DURING RE-SOLDERING PROCESS . LACK OF GOOD MECHANICAL STABILITY ON OUTSIDE PLATE HOLDING BNC CONNECTORS. NO LOCKING WASHERS USED ON OUTSIDE PLATE TO DETER SCREWS FROM TURNING WHICH IN TURN WOULD CAUSE DE-TUNING OF CAVITIES. SLIGHT BEND IN FRONT PLATE HOLDING BNC CONNECTORS, LACKS SUPPORT IN CENTRE.

CHARACTERISTICS

SPECIFICATION SHT 1

SPECIFICATION SHT 2

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