I have a chance to buy what looks like a mint-condition, fully functioning Sansui 5000a receiver. Price would be $175, which seems perhaps a little steep to me since it has not been updated or worked on at all. Does anyone know if there is a way to tell if it has the 1040 amp boards with fire issues just by looking at serial number? The SN is 220061030, which looks like a June 1970 manufacture date after some cursory research.