Fault Analysis: After shutting down the machine, the AC power voltage was measured to be 220V, which is normal. Inspection of the power circuit also revealed no issues with virtual soldering. It is possible that there might be a problem with the high and low voltage protection circuits.
Data Source: Beijing Siemens Washing Machine Repair Phone http://blog.tianya.cn/blogger/blog_main.asp?BlogID=3432932. Siemens Washing Machine, Beijing Siemens Washing Machine Repair Center, when the power is connected, an immediate alarm sounds.
Fault Inspection: Referring to the microprocessor program controller electrical schematic diagram of this washing machine, in the circuit, the grid voltage sampling resistor R35 undergoes half-wave rectification through diode D9, forming a DC voltage on R36 that changes synchronously with the grid voltage. This is then clamped by diode D7 and filtered by capacitor C11 before being input into pin 12 of microprocessor IC1. The microprocessor detects this value to perceive changes in the grid voltage. When the grid voltage is too high, the microprocessor program controller generates an alarm signal and shuts down; when the grid voltage is too low, it shuts off all outputs and displays accordingly.
After disconnecting the power, check related components such as ZNR1, C22, R35, T1, D9, C23, D7, and C11. It was found that capacitor C23 had severe leakage, causing the microprocessor program controller to work abnormally, leading to an immediate alarm upon connecting the power. Replace capacitor C23 (47F/10V), conduct a trial run after turning on the machine, and the washing machine operates normally, resolving the fault.