Detection circuit in power supply, 12V normal 5V2 measured 0V power supply, due to 5V2 voltage, T503 transformers (11) leg by ZP53 current VD522 rectifier, C548 filtered output voltage of 10V, 10V voltage output normally measured and V571 collector voltage-free, so no 5V2 output measured R572 is open circuit, replace R572, everything is normal.