POTENTIAL CONFLICT AIRBORNE BETWEEN ACR-MLG AND GA-SMA.

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AT APPROX XA21Z; 11 DME SW OF MDW AT 3300'; DSNDING TO 3000'. RADAR VECTORS MDW I SPOTTED A SINGLE ENG SMA AT 12 O'CLOCK POS JUST BELOW THE NOSE OF MY ACFT. WE WERE IN A VERY SHALLOW DSCNT LEVELING AT 3000'. THE F/O WAS FLYING THE ACFT AND I POINTED OUT THE TFC AND MADE A GRADUAL LEFT TURN; ABOUT 20 DEGS LEFT. CHICAGO APCH AT THIS TIME GAVE US A RIGHT TURN TO ? WHICH I COULD NOT ACCEPT DUE TO THE TFC. I WAS THEN ASKED WHAT I WANTED FOR A HDG. I REPLIED WITH EITHER PRESENT HDG OR LEFT TURN. WE WERE THEN ASSIGNED HDG 180 DEGS. I HAD BEEN ON ASSIGNED HDG 290 DEGS FOR THE VECTOR TO RWY 4R MDW AND HAD ALREADY TURNED TO A 270 DEG HDG TO AVOID THE CONFLICT TFC IN ORDER TO KEEP HIM IN SIGHT IN CASE HE MADE A TURN TOWARDS US. HE; THE SMA; WAS LEVEL AT 3000' AND APPROX HDG OF 290 DEGS. THE CTLR WAS VERY BUSY AND HAD NOT GIVEN ANY ADVISORIES AND LATER SAID HE DID NOT SEE THE OTHER TFC UNTIL AFTER WE HAD ALREADY PASSED CLR OF IT. LUCKILY THE OTHER ACFT WAS SPOTTED IN AMPLE TIME TO AVOID ANY ABRUPT MANEUVERS. PERFECT SET UP FOR MIDAIR. CLEAR; VIS UNLIMITED; HOLIDAY WEEKEND AND A VERY BUSY CTLR. DISCOVERED BY OUTSIDE VIGILANCE ON BEHALF OF CREW. CORRECTIVE ACTION: GUESS WE NEED TO UPGRADE THE SYSTEMS; MORE FULL PERFORMANCE CTLRS; AND I HATE TO SAY IT; BUT IF AN SMA (OR FOR THAT MATTER; LARGE PLANES) OPERATE IN THE VICINITY OF BUSY TERMINAL AREAS; THEY NEED TO HAVE THE APPROPRIATE EQUIP IN PROPER WORKING ORDER.