What was found
RTBETA-LIGHT CAME ON DURING TAKE-OFF ROLL. PROPELLER RPM DROPPED HEAVILY. PULLED CIRCUIT BREAKER. RPM RETURNED TO NORMAL. FOUND ALL SINGLE WIRE INSULATIONS IN WIRE BUNDLE TOENGINE/PROP SWITCHES, INCLUDING DE-ICE WIRES AT REDUCTION GEAR BOX HARDENED AND BROKEN, MAKING CONTACT. WIRE BUNDLE RUNS UNDERNEATH EXHAUST FLANGE. NO OTHER DAMAGE DUE TO FAST PULLING CIRCUIT BREAKER, IF THIS HAPPENS DURING FLIGHT, IT COULD LEAD TO A DANGEROUS SITUATION. REPLACED ALL WIRING.