/Circuit board fault 7 major inspection and repair methods
1. Visual inspection
Check for faults by sight, smell, hearing and touch.
Visual inspection is wrong in wiring, welding spot and components, after making sure there is no error, the battery is installed, after energizing the radio, there is no difference sound, if no difference sound has burnt smell, and hand touch transistor to see if it is hot, see if the point unsoldering capacitance has crack.
MF47 multimeter is used to detect whether the resistance value of the resistance components in the circuit is correct, check whether the capacitance is broken, breakdown or leakage, and check whether the crystal diode and transistor are normal.
3. The method of voltage
MF47 type multimeter dc voltage file is used to test the power supply. If the static working voltage of the quality tube is correct, if not, the reason can be found, and the ac voltage value can also be detected.
4. Waveform method.
When the circuit waveform is checked by an oscilloscope, it needs to be carried out when there is an external signal input, and the output waveform of each transistor is checked by an oscilloscope.
5. Current method
MF47 type multimeter dc voltage level is used to detect the static current of the collector to see if it meets the standard.
6. Replacement of components and components
If it is suspected that a component is defective, it can be replaced by an intact component of the same specification.If the circuit works properly after replacement, the original replacement component has been damaged.This method should not be used for expensive components, because it will cause unnecessary waste if the components are not damaged. For costly components, they can only be replaced after determining the damage.
7. Classification separation method
The stepwise search separation method can go to the former level and backward level to check the method, also can adopt the method of forward level from the rear level.Set test breakpoints at all levels, so that you can narrow down the scope of the test during testing, and make it easier to check where the failure point is.
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