What was found
PIT FLT 1991 ENROUTE PHL TO ORD. ON GEAR RETRACTION THE NOSE GEAR RED LIGHT ILLUMINATED. THE FLIGHT DIVERTED TO PIT. DURING APPROACH, UPON GEAR EXTENSION, THERE WAS INITIALLY A 3 GREEN, DOWN AND LOCKED INDICATION. A FEW MOMENTS LATER, THE NOSE GEAR GREEN INDICATION EXTINGUISHED, AND THE GEAR HORN SOUNDED. HOWEVER, THE RED GEAR INDICATION DID NOT ILLUMINATE. THE FLIGHT DID A FLY BY OF THE TOWER AND AFTERWARDS PROCEEDED TO LAND WITHOUT FURTHER INCIDENT. MX REPLACED PRINTED CIRCUIT CARDS M983 AND M1214. PERFORMED SEVERAL GEAR SWINGS. OPS CHECK NORMAL.