What was found
(CAN) LOSS OF INSTRUMENT LIGHTING ON CPT AND COPILOT INSTRUMENT PANEL. LIGHTS CONTROLLED BY 2 SEPARATE POTENTIOMETERS ON OVERHEAD PANEL. PROBLEM ACTUATED C/B 21 LOCATED UNDER FLOOR WHICH FEEDS BOTH INSTRUMENT PANEL LIGHTS. MAINT FOUND THAT BEHIND AUDIO SELECTOR PANEL, WIRE L33J20 WAS CHAFED ON CENTER FORMER STA 94. NOTED THAT L33J20 WAS NOT SECURED TO ANYTHING. WIRE L33J20 FEEDS POST LIGHTS ON INSTRUMENT PANEL AND IS FED FROM TB118 TERMINAL 7 WHICH IS CONTROLLED BY C/B 21. SHORT ALSO CAUSED TRANSISTOR Q5 WHICH CONTROLS PILOT FLIGHT LIGHTS TO SHORT OUT. THE CHAFED WIRE WAS SECURED, TRANSISTOR REPLACED, C/B 21 RESET. SUBMITTER SAYS FEED TO 2 PILOTS SHOULD BE SEPARATED AND OFF 2 C/B'S.