Bosch washing machine PCB board repair
If you have no experience with electronics, it is better to entrust the repair of the Bosch washing machine control board to specialists. The module consists of dozens of semiconductors, tracks and microcircuits. Without understanding the device of the unit, you can harm the controller even more. When you have some knowledge, you can perform diagnostics and repair the element yourself. We will tell you how to do this.
Elements of the control and indication board of the Bosch SM
Problems with the main control unit of Bosch washing machines rarely occur. The board most often burns out due to external influences - moisture getting on the semiconductors or power surges in the electrical network. The module controls the entire operation of the washing machine, so if it is damaged, the washing machine cannot function normally.
It is not difficult to dismantle the control unit. It is enough to pull out the powder receptacle, remove the top cover of the machine and the dashboard, reset the wiring and unscrew the bolts that fix the board. Now we will tell you what parts the "brain" of the Bosch washing machine consists of.
The controller of most Bosch washing machines consists of a main unit and an indicator unit. They are interconnected. Each element is responsible for certain functions. The main board contains:
- Program selector,
- Power unit,
- Capacitors,
- Hf transformer,
- Rectifier diodes,
- Varistor,
- Thyristors (each controls the operation of different elements of the washing machine: drain pump, hatch locking device, inlet valves, etc.),
- Voltage stabilizer,
- Resistor,
- Microcontroller,
- Thyristor block,
- Engine control thyristor,
- Relays responsible for reversing the engine and turning on the heating element.
The indication board is connected to the main unit with a special cable. It contains:
- LEDs,
- Touch button antennas,
- High frequency NPN transistors,
- Microcircuits for indicators,
- Driver that controls the operation of LEDs,
- Voltage stabilizer,
- Capacitors,
- Microcontroller,
- Buzzer (a device that makes a sound when the washing machine is turned on and at the end of the cycle).
The electronic unit is the "brain" of the washing machine. It controls the execution of any washing programs. Bosch washing machine modules consist of one or two boards - this depends on the model of the washing machine. Each part contains semiconductors responsible for the operation of different units of the machine. The elements are connected to each other by tracks.
If the electronic unit is damaged, the machine may not turn on at all or not respond to user commands, or "freeze" at a certain stage of the cycle. If all other possible failures are excluded, you will have to check the functionality of the control board. We will tell you how diagnostics are performed.
Checking the control board elements
The electronic unit of the Bosch washing machine usually fails due to voltage fluctuations in the network. Therefore, if the light in the apartment was flickering, and after that the machine stopped turning on, most likely the board burned out. Another possible reason is high humidity in the room and water getting on the semiconductors.
If the board is clean in appearance, there are no burnt areas or black spots on it, you will have to ring each semiconductor. Diagnostics of the control unit is performed with a multimeter. The tester is switched to the "ringing" mode.
After the pulse power supply on the main module there is a smoothing capacitor. The outputs of this capacitor should ring with the contacts of the connectors going to the indication board. If the multimeter beeps, then both parts "communicate" with each other.
The capacitors on the control board are responsible for voltage stabilization. An obvious cause of element failure is its swelling. The capacitor contacts are also rung with a multimeter. A one on the tester screen will indicate a break, zero - a short circuit.
