What was found
FLT 9280, IMMEDIATELY AFTER TAKEOFF, GOT LT ENVIRONMENTAL FAIL ANNUNCIATOR ILLUMINATED. CYCLED BLEED VALVE SWITCH AND LIGHT WENT OUT. TEN MINUTES LATER DETECTED SMOKE AND MELTING PLASTIC ODOR. CYCLED BLEED SWITCH OFF AND SMELL STOPPED. NOT NECESSARY TO USE OXYGEN MASK OR SMOKE GOGGLES. DETERMINED LT PRESSURE REGULATOR SHUTOFF VALVE (PRSOV) CLAMP TO BE LOOSE ALLOWING HOT BLEED AIR TO BLOW ONTO ADJACENT WIRE BUNDLE. INSPECTED WIRE BUNDLE AND DID NOT DETECT ANY DAMAGE. RESECURED PRSOV CLAMP WITH A SATISFACTORY LEAK CHECK.