What was found
FLT 234, LGB-SLC, AIR RETURN TO LGB, LAND ASAP IN AMBER AFTER TAKEOFF. NO OTHER ABNORMAL INDICATIONS. DUE TO HISTORY OF FAULT T/S PER TSM 21-26-00-810-811 COULD NOT DUPLICATE FAULT. REPLACED SMOKE WARNING RELAY (2WA) PRECAUTIONARY, ALSO DIODE MODULE (1800VD). CHECKED OK. SUSPECT FAULT IN FWC'S. REMOVED AND REPLACED FWC 1 & FWC 2 PER 31-53-34-04 AND 31-51-00-03, OPS CHECK OK, NO FAULT NOTED.