(1) Preparation before installation

(1) check whether the printed board has quality problems;

② All components must be tested before installation;

(3) Take the soldering iron and prepare for welding.

(2) Inspection of components

Firstly, compare the principle circuit diagram to understand the printed circuit diagram. Compare the elements in the circuit diagram with the physical elements to understand the physical elements. Then test the component.

① List the components according to the principle circuit. Draw a list of components.

② Check the test resistance and capacitance parameters one by one. Measure the capacitance of small capacity capacitor with digital multimeter. The circuit has no special requirements for resistance and capacitance.

③ Check whether the potentiometer is in good condition.

(3) Lead forming of electronic components

When installing electronic components on the circuit board, the pins of the components must be preformed to meet the needs of circuit installation. Lead forming of electronic components is mainly to make the mounting size of components meet the requirements of the mounting hole size of components on printed circuit boards.

(4) Insertion method of electronic components

① Insertion sequence: first low, then high, first small, then big, first light, then heavy.

② Component identification: the marks and color codes of electronic components should be upward for easy identification; The numerical reading of horizontal plug-in should be from left to right, while the numerical reading of vertical plug-in should be from bottom to top.

③ Component spacing

The distance between components on the printed circuit board should not be less than1mm; Lead spacing should be greater than 2mm. Generally, components should be installed tightly so that they can be attached to the printed circuit board.

Components that meet the following conditions should not be installed tightly, but should float:

A, the axial lead needs to be inserted vertically: the general components are 3 ~ 7mm； away from the printed board;

B. Components with high calorific value (high-power resistors, high-power tubes, etc.). );

C devices whose performance tends to deteriorate after heating (such as integrated blocks);

④ Pay attention to the polarity of diodes, integrated circuits and electrolytic capacitors.

Because there are few components in this circuit board, the components are installed in the order of diode, resistor, potentiometer, small electrolytic capacitor, large electrolytic capacitor and integrated circuit.

Before installation, pay attention to whether the pins of the components are oxidized, and deal with the components with serious oxidation and tin plating.

2. Welding of 2.DC regulated power supply

Check according to the drawing, and then weld after it is correct. In order to ensure the reliability and not damage the printed circuit board, special attention should be paid to controlling the temperature of the soldering iron by mastering the welding time to prevent virtual welding and copper foil peeling.