LESS THAN STANDARD SEPARATION BETWEEN CLIMBING AND DESCENDING MLG ACFT; ATC RADIO COM PROBLEM AND CTLR TECHNIQUE.

Narrative

MLG X WAS LEVEL AT FL330 AND GIVEN CLRNC TO DSND AND MAINTAIN FL240 AND TOLD TO START THE DSCNT NOW; MLG Y WAS LEVEL AT FL310 REQUESTING FL350 WAS CLBED TO FL330. MLG Y WAS CLBING AT A VERY GOOD RATE OF CLB SINCE HIS PIT DEP. THE ACFT WERE 40 MI APART AT THE TIME OF THE CLRNCS. MLG X WAS NOT DSNDING AT A NORMAL RATE OF DSCNT (ONLY 400' IN OVER A MINUTE AFTER RPTING LEAVING FL330). CTLR TRIED TO EXPEDITE HIS DSCNT BUT THE FREQ WENT DEAD. I TRIED TO KEY THE MIC A FEW TIMES AND PLAYED WITH THE HEADSET JACK TO SEE IF THE XMITTER LIGHTS WOULD COME ON. IT WAS OBVIOUS THAT NOTHING WAS XMITTING. THE FREQS DID COME BACK WHEN THE ACFT WERE ABOUT 12 MI APART AND CTLR TIRED TO PUSH HIM DOWN AND GET A RPT OUT OF FL310 (MLG Y HAD BEEN LEVEL AT FL330 LONG BEFORE); BUT IT WAS TOO LATE. HAD THE FREQ NOT FAILED; THERE IS NO QUESTION THAT STANDARD SEP COULD HAVE BEEN MAINTAINED. THE RELIEVING CTLR ALSO HAD PROBS WITH THAT FREQ AND IT WAS LOGGED OUT TO BE REPAIRED. CTLR USED JUDGEMENT TECHNIQUE OF INITIAL CLRNCS TAUGHT BY TRNING DEP AT CENTER. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING: RPTR WAS ABOUT TO BE RELIEVED AND TRACKER AND OTHER CTLR HAD PLUGGED IN ABOUT THE TIME OF THE INCIDENT. ACFT WERE APPROX 1600' AND 3 MI AT CLOSEST POINT. TFC VOL WAS LIGHT TO MODERATE. NO TFC ADVISORIES WERE GIVEN PRIOR TO OR AFTER INCIDENT; BUT ACFT DID RPT SEEING EACH OTHER. RPTR SAYS SAME THING HAPPENED TO RADIO ABOUT 10 DAYS LATER; COULD BE A JACK PROB.