The printed circuit diagram is closely related to the repair, the importance of repair is only second to that of the whole mechanical and electrical principle diagram, so the printed circuit diagram is mainly for repair service.
1. types of printed wiring
The printed circuit diagram has the following two forms:
(1) drawing representation
At this point, with a drawing (called the printed circuit diagram) to draw the distribution of components and the connection between them, which is the traditional way of expression, in the past a lot of use.
(2) direct calibration method
Without a special printed circuit drawings. At this time, but to take direct labeling number on the circuit board components, such as a transistor in the circuit board near the marked 1VT2, this is the 1VT2 transistor in the electrical principle diagram of the number in the same way, the various components of the circuit number directly marked on the circuit board. This method is widely used in imported machines, in recent years, a large number of domestic machines are also used in this way.
2. print circuit function
A printed wiring diagram is a diagram for the assembly and repair of components, which is essentially different from the various circuit diagrams. The main functions of the printed wiring diagram are as follows:
The printed circuit diagram to connect between the electrical principle diagram and the actual circuit board, convenient repair is one of the indispensable drawings, no printed circuit diagram will affect the repair speed, and even hinder the normal way of examination smoothly.
Printed circuit diagram is a very important repair material, it will be printed on the circuit board one by one on the printed circuit diagram.
The printed circuit diagram shows the distribution of the components in the circuit diagram and the specific position of the circuit board.
3. printed circuit diagram features
The printed circuit diagram has the following characteristics:
The printed circuit diagram components with circuit symbols, each connection between components without lines with copper lines, some also use copper foil circuit connected with the transconductance, line connection, so the printed circuit diagram looks "chaos", the influence of knowledge map.
Starting from the effect of the printed circuit design, the arrangement and distribution of the components on the circuit board is not as regular as the electrical schematic diagram, which brings a lot of inconvenience to the understanding of the printed circuit diagram.
The arrangement of copper wire and the tendency of "chaos", and often encounter a number of parallel arrangement of copper foil, copper foil to observe the direction of the inconvenience.
There are all kinds of lead wires on the printed circuit drawing, and the drawing of these leads is not fixed.
4. methods and skills of drawing and drawing
Because of the "chaos" of the printed circuit diagram, the following methods and techniques can be used to improve the speed of drawing:
Although the distribution and arrangement of components are not regular, the components in the same unit circuit are relatively concentrated.
According to the characteristics of some components can be found in these components, such as integrated circuits, power amplifiers, switches, transformers, etc.. For integrated circuits, a specific integrated circuit can be found based on the model of the integrated circuit.
Some cell circuits are more characteristic, which can be easily found according to these features. If the rectifier circuit in the diode is more, the power amplifier has a heat sink, the largest capacity of the filter capacitor, the largest volume, etc..
To find a resistor or capacitor, don't go directly to them, because the resistor, the capacitor circuit for many, it is not convenient, they can be found indirectly, method is to find which is connected with the transistor or integrated circuit, find them again.
When finding the ground wire, a large area of copper wire on the circuit board is a ground wire. In addition, some components of the metal shell is grounded. Any of the above can be used as a ground wire. In some of the various layers of the circuit board, the ground wire is also connected, but when the connector between each layer is not connected, the ground between the layers is not a barrier, which should be noted in the maintenance.
5, repair and understanding of the methods and matters needing attention
The repair drawing is the analysis of the circuit diagram in the repair process, which is very different from the understanding of the working principle of the circuit.