What was found
ON TAKEOFF FROM DSM ,THE LT PACK TRIPPED AND THE LT DUCT OVERHEAT LIGHT ILLUMINATED. THIS WAS ACCOMPAINED BY THE USUAL ODOR OF A PACK OVERHEATING AND SMOKE IN THE COCKPIT. QRH PROCEDURES ELIMINATED THE SMOKE & REESTABLISHED THE LT PACK. GIVEN THE OUTSIDE AIR TEMP AT DSM OF 21*C THERE IS NO EASY EXPLANATION OF WHY THE LT PACK WOULD PRODUCE THESE PROBLEMS; NOTE; THAT THIS IS THE 2ND INCIDENT IN THE PAST WEEK OF SMOKE IN THE COCKPIT. CLOSED J-4 BOX AND E&E COMPARTMENT. R & R LT PACK COOLING FAN REF AMM 21-56-091-4. CLOSED UP ALL ACFT BAY ACCESS PANELS. OPS CHECK OF LT PACK IS GOOD REF JRH CHAP 8. NO SMOKE SMELL OR HIGH PACK TEMP ON LT PACK. ACFT OK FOR SERVICE.