What was found
WHEN GEAR WAS SELCTED DOWN THE ANTI-SKID ANNUNCIATOR ILLUMINATED AND ABOUT 60 TO 90 SECONDS LATER POWER BRAKE CIRCUIT BREAKER TRIPPED. RESET THE CIRCUIT BREAKER & WITHIN 60/90 SECONDS THE POWER BRAKE CIRCUIT BREAKER TRIPPED AGAIN. TROUBLESHOOTING REVEALED CORROSION ON BATTERY GROUND BUS BAR AND GPU GROUND BUS BAR, SIGNIFICANTLY AFFECTING GROUND INTEGRITY FOR THE BATTERY, LT & RT STARTER/GENS, GPU, & APU. BOND CHECKS CONDUCTED PER SPM 20-30-10, FINDING OUT-OF-TOLERANCE READINGS PRIOR TO CLEANING. AFTER ADDRESSING CORROSION & REPLACING THE GPU GROUND BUS BAR IAW MM 24-41-00, ALL SUBSEQUENT BOND CHECKS RETURNED ACCEPTABLE VALUES, CONFIRMING CORROSION AS THE PRIMARY ISSUE IMPACTING GROUND CONNECTIONS.