What was found
AIR TURN BACK, ENROUTE, THE CAPT`S VSI FLASHED MOMENTARILY CAUSING A TCAS FAIL AND RESOLUTION ALERT, THEN WENT BLANK. SINCE THE COPILOT`S SYSTEM WAS OPERATING NORMALLY. A DECISION TO RETURN TO DEPARTURE WAS MADE SINCE PARTS WERE AVAILABLE THERE AND MAINTENANCE ALSO COULD BE ACCOMPLISHED. REMOVED AND REPLACED CAPT`S VSI/TCAS INDICATOR. (K)