What was found
AIRCRAFT CAME IN FOR GENERATOR PARALLELING. LEFT GENERATOR CONTROL UNIT NEEDED REPLACEMENT. INSTALLED OVERHAULED GCU S/N 10853A; GCU FAILED ON INITIAL RESET. INSTALLED SECOND GCU S/N 9183; GCU FAILED ON INITIAL RESET. (BOTH ABOVE GCU'S HAD JUST BEEN OVERHAULED BY PRECISION ELECTRONICS, INC., ATLANTA, GA FOR THE SAME INITIAL FAILURE PROBLEM). INSTALLED A THIRD GCU S/N 9657; WHICH FUNCTIONED CORRECTLY. (ALSO OVERHAULED BY PRECISION ELECTRONICS, INC.)