What was found
DURING COCKPIT PREFLIGHT, NOTICED HEAVY WHITE SMOKE COMING FROM OVERHEAD CONTROL PANEL. ADVISED 2ND OFFICER TO REMOVE ELECTRICAL POWER FROM ACFT. ADVISED CREW TO EVACUATE. INSP O/H PANEL AREA & FOUND NO SIGNS OF BURNED WIRES, SWITCHES, CONNECTOR'S OR RELAYS, OPENED PANEL JUST AFT OF OVERHEAD PANEL & INSPECTED AREA FOR BURNED WIRES, CONNECTORS OR RELAYS AND FOUND RELAY R70 FOR EMERGENCY LIGHTS OVERHEATED & FOUND EVIDENCE ON RECEPTICAL & AREA AROUND RECEPTICAL OF AREA BEING OVERHEATED. R & R R70 RELAY, CONGFIGURED COCKPIT AS FLT CREW WOULD FOR PRE-DISPATCH CHECK. RAN APU FOR APPROX 1 HR & HAD NO EVIDENCE OF SMOKE. EMERGENCY EXIT LIGHT SYS OPS CHECK'S NORMAL. ACFT OK FOR CONTINUED SERVICE.