Article Source: Beijing Bosch Washing Machine Repair Phone http://blog.tianya.cn/blogger/blog_main.asp?BlogID=3446026. Bosch Washing Machine, after the job is done, the buzzer does not sound.
Fault Analysis: According to the fault phenomenon analysis, there may be three possible fault points:
(1) Microprocessor 14021WFW.
(2) Buzzer drive circuit.
(3) Buzzer piezoelectric ceramic sheet BY.
Fault Inspection: First, check the piezoelectric ceramic sheet BY and its connections, both of which show no abnormalities. Then, check the output level of pin 19 on the microprocessor 14021WFW, which appears basically normal. It is estimated that the fault lies in the buzzer drive circuit. After power-off, use a multimeter to check related components including transistors BG5, BG12, BG13, resistors R17, R18, R19, R38, R39, R26, R27, etc., Beijing Bosch Washing Machine Repair Phone, and find that the collector of BC13 is open-circuit. Replace transistor BC13, turn on the machine for testing, the buzzer sounds normally, and the fault is eliminated.