ZFW CTLR EXPERIENCED OPERROR AT FL340; INITIALLY ISSUING A WRONG DIRECTION TURN; THEN CORRECTIVE ACTION ISSUED TOO LATE FOR SEPARATION DUE TO COM FAILURE.

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ACFT Y; AN LJ31; WAS CLBING OFF OF LBB REQUESTING FL410. ACR X DEPARTED DFW WAS NWBOUND AT FL340. AN INTERNAL LOA WOULD HAVE ACFT Y CLBING TO FL290 ENTERING MY SECTOR 47. INITIALLY; THE PREVIOUS SECTOR 93 WAS GOING TO RELEASE CTL TO FL370 VIA THE LOA; AND WOULD NEVER TALK TO THE ACFT. ZFW IS IN THE PROCESS OF CONSOLIDATING 7 AREAS TO 6 AND SECTOR 93 WILL BECOME PART OF MY AREA. THE SECTOR HAS BEEN PHYSICALLY MOVED RIGHT NEXT TO 47. THESE ARE 2 LARGE; FREQUENTLY BUSY SECTORS AND IT CAN BE HARD TO HEAR YOURSELF THINK WHEN BOTH ARE BUSY. A CPC FROM OUR AREA WAS TRAINING ON 93 D-SIDE. HE SAW MY TFC AT FL340; OVERRODE THE LOA; TOOK RADAR CONTACT ON ACFT Y AND COORD A CLB TO FL330 WITH US. HE RELEASED CTL OF ACFT Y AT 4 MINS FROM CONFLICTION; VECTOR LENGTHS INDICATED ACFT Y WOULD PASS 7 MI BEHIND ACR X. ACFT Y GND SPD WAS INCREASING IN THE CLB. I INTENDED TO TURN ACFT Y 10 DEGS R AND CONTINUE THE CLB TO FL350 (I HAD OTHER TFC AT FL360). ACFT Y WAS CLBING AT 1500 FPM AND WOULD TOP ACR X BEFORE THE CONFLICT POINT. THE SECTOR 93 R-SIDE; WHO IS KNOWN TO NOT SWITCH ACFT TO THE NEXT SECTOR UNTIL WELL AFTER HIS CONFLICTS ARE RESOLVED (AS PER 7110.65R) DID NOT SWITCH ACFT Y UNTIL THE COMMON BOUNDARY. I WAS SITUATIONTING RIGHT NEXT TO HIM AND COULD SEE HE HAD NO TFC FOR ACFT Y. WHEN ACFT Y CAME TO MY FREQ; HE WAS LEVELING AT FL330; WHICH MEANT HIS GND SPD WOULD BE INCREASING AND HE WOULD PROBABLY TAKE ANOTHER 20-30 SECONDS TO RESUME HIS CLB. I INTENDED TO TURN HIM 15 DEGS RIGHT NOW. I HAD BEEN ON POS OVER 1 1/2 HRS WITH STEADY TFC AND WORDS AND CALL SIGNS BEGIN GETTING TRANSPOSED. I SAID 'TURN 15 DEGS L; CLB AND MAINTAIN FL350.' WHEN I HEARD THE READBACK; I RECOGNIZED MY MISTAKE AND IMMEDIATELY CORRECTED IT TO A R TURN. I GOT NO RESPONSE SO REPEATED THE CLRNC. I GOT NO RESPONSE; SO I CALLED FOR ACFT Y WITH NO ANSWER I SCANNED THE REST OF MY SECTOR AND TRIED AGAIN. ACFT Y RESPONDED AND I TURNED HIM 30 DEGS R. SEPARATION WAS LOST 30 SECONDS LATER. THE LOSS OF COM AFTER THE INCORRECT CLRNC IS CRITICAL. PLTS HAVE NO ACCOUNTABILITY FOR COMS IN THE PRESENT SYS. THE FAA'S CURRENT 'FIX ON FAIL' POLICY FOR EQUIP MAINT MAY BE A FACTOR. THERE ARE CURRENTLY AT LEAST 2 'DEAD SPOTS' IN OTHER AIRSPACE THAT WE CONSISTENTLY LOSE CONTACT WITH ACFT AROUND FL200. ACFT Y MAY HAVE HIT A 'DEAD SPOT.'