SMT X HAD LTSS FROM ACR Y. SYS ERROR.

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I APPROVED A ZOA (SECTOR 45) REQUEST FOR SMT X TO ENTER MY AIRSPACE DSNDING TO FL140 ON V165 NW OF FMG. ACR Y WAS INBOUND ON THE SAME AIRWAY DSNDING TO FL160. ACR Z WAS ALSO INBOUND VIA ANAHO INTXN; AND WAS ASSIGNED HDG 240 DEGS BY ZOA. I EXPEDITED BOTH ACR Z AND X THROUGH FL150 TO MAKE ROOM FOR ACR Y TO ENTER MY AIRSPACE. I VECTORED Z TO THE ARPT TO BE #1. I VECTORED X TO A HDG OF 200 DEGS TO TAKE HIM W TO FINAL WHERE HE COULD BE SEQUENCED LATER. I TURNED Y E TO HDG 100 DEGS BOTH FOR DSCNT; AND TO FOLLOW Z. I TURNED Y W TO HDG 230 DEGS TO BRING HIM BACK TO THE FINAL. I SLOWED Y TO 210 KTS; AND GAVE HIM CLRNC TO DSND THROUGH X'S ALT; AND CLRED HIM FOR A VISUAL APCH TO RWY 16L 1-2 NM NE OF SPK NDB. Y DID NOT TURN TOWARD THE ARPT; AND APPEARED TO FLY THE GND TRACK OF THE SPARKS VISUAL RWY 16R APCH (A CHARTED VISUAL APCH TO RNO). WHEN I CLRED Y FOR A VISUAL APCH; I ATTEMPTED TO TURN X W TO HDG 230 DEGS; BUT I WAS BLOCKED BY Y. I LATER GAVE X AN IMMEDIATE R TURN TO TRY TO SAVE AS MUCH SEPARATION AS POSSIBLE. X WAS SURPRISED BY MY IMMEDIATE TURN; AND DID NOT TURN. I THEN ISSUED TFC TO Y WHO SAW THE CY21. SEVERAL PROCEDURAL FACTORS AND MISTAKES BY ME CONTRIBUTED TO THIS INCIDENT. X WAS INBOUND ON THE SAME RTE OF FLT AS Y; AND FORCED ZOA TO KEEP Y ON THEIR FREQ AND ABOVE MY AIRSPACE. THIS FORCED ME TO TAKE Y OFF FINAL BECAUSE HE WAS TOO HIGH TO MAKE A STRAIGHT IN APCH. WHEN I CLRED Y FOR A VISUAL APCH HE WAS STILL HIGH; BUT IN MY OPINION SHOULD HAVE BEEN ABLE TO PROCEED STRAIGHT IN TO THE ARPT. Y WOULD NOT HAVE BEEN IN CONFLICT WITH X HAD THEY TURNED STRAIGHT IN. Y APPEARED TO FLY THE SPARKS VISUAL APCH; BUT MAY HAVE GONE W OF FINAL TO ALLOW ROOM FOR DSCNT. WHEN ZOA HANDED OFF Y I FELT IT WOULD BE POSSIBLE TO FIT ALL THE INBOUND ACFT INTO A SEQUENCE; BUT I WOULD HAVE VERY LITTLE ROOM FOR ERROR. I SHOULD HAVE KEPT Y AT A HIGH ALT AND VECTORED THAT ACFT INTO ANOTHER TFC FLOW; EFFECTIVELY TAKING Y OUT OF THE SEQUENCE. ONCE I DECIDED TO SEQUENCE Y TO THE ARPT I SHOULD HAVE ANTICIPATED Y GOING THROUGH FINAL; AND VECTORED X W SOONER. I ALSO HAD A PROB WITH FREQ CONGESTION. I WOULD WAIT AS LONG AS I COULD FOR A READBACK BEFORE ISSUING ANOTHER INSTRUCTION. ON 2 OCCASIONS INSTRUCTIONS WHICH WOULD HAVE PROVIDED SEPARATION WERE BLOCKED BY ACFT GIVING A DELAYED READBACK OF A PREVIOUS INSTRUCTION. IF I HAD QUICKLY RE-ISSUED INSTRUCTIONS; OR WAITED FOR AN ACFT TO READ BACK THEIR INSTRUCTIONS; SEPARATION WOULD HAVE EXISTED.