What was found
(CAN) AFTER STARTING ENGINE FOR GROUND RUN, AVIONICS SWITCH WAS SELECTED ON. IMMEDIATELY SMOKE STARTED COMING FROM RT CB PANEL. ENGINES WERE IMMEDIATELY SHUTDOWN AND POWER WAS REMOVED FROM A/C. INVESTIGATION REVEALED THAT A FACE PLATE MOUNTING SCREW HAD SHORTED TO AN AVIONICS FEEDER WIRE P72A10 DUE TO POOR ROUTING OF THE WIRE AT MFG. (2) 10GAUGE WIRES ARE ATTACHED TO ONE TERMINAL OF CB120 (TCAS), ONE COMING FROM CB92 (AVIONICS POWER LT GEN BUS) WHICH IS A 30AMP BREAKER. ONE OF THE WIRES WAS MOUNTED ALONG THE BACK OF THE PANEL AND HAD BEEN IN HARD CONTACT WITH THE AFT MIDDLE FACE PLATE MOUNTING SCREW. WIRE REPLACED IAW AC43.13-1B PARA 11-98, ROUTED TO AVIOD CONTACT WITH MOUNTING HARDWARE. (TC NR 20071130015)