1、 Visual inspection method for SMT
SMT patch faults can be detected through visual, olfactory, auditory, and tactile inspection.
Visually inspect the wiring, SMT solder joints, and components for any errors. Once confirmed to be correct, install the battery and power on the radio to check for any abnormal sounds. If there are no abnormal sounds, check for any burnt smell. Touch the transistor with your hand to see if it is hot and if there is any swelling or cracking of the electrolytic capacitor.
2. Resistance method
Use the MF47 multimeter to check whether the resistance of the resistor chip components in the circuit is correct, check whether the capacitor is broken, broken or leaking, and check whether the crystal diode and transistor are normal.
3、 Voltage method
Use the DC voltage range of the MF47 multimeter to check whether the static working voltage of the power supply and transistor is correct. If it is not correct, identify the cause and also detect the AC voltage value.
4. Waveform method
Use an oscilloscope to check the circuit waveform, which needs to be done with external signal input. Use an oscilloscope to check the output waveform of each transistor.
5、 Current method
Detect the static current of the collector of the transistor using the DC current range of the MF47 multimeter to see if it meets the standard.
6、 Component substitution method
After the above inspection, if there is suspicion of a problem with a certain component, it can be replaced with a component of the same specification and in good condition. If the circuit works normally after replacement, it indicates that the previously replaced components have been damaged. This method is not suitable for high cost components because if it is not for component damage, it will cause unnecessary waste. For high cost components, they must be replaced after confirming the damage.
7、 Step-by-step inspection and separation method
The step-by-step investigation and separation method can adopt the method of investigating from front to back, or from back to front. Set test breakpoints between different levels, so that the detection range can be narrowed down and the fault location can be more easily detected during testing.
