Several principles of circuit board maintenance

Electronic technology hardware skills deep maintenance staff on the maintenance work full of confidence, but if the method is not working properly it still less effective. So how can we better improve the efficiency of maintenance?

This is the following discussion of several principles for peer reference, so that the maintenance work in an orderly manner in a step by step.

Principle 1: first look after the amount

The circuit board to be repaired should first be visually inspected and, if necessary, by means of a magnifying glass.

1. Is there a broken line and short circuit; especially the printed circuit board on the circuit board is the existence of fracture adhesion and so on;

2. Whether the components such as resistance and capacitance inductor diode transistor, etc. whether there is disconnection;

3. Has anyone ever repaired the components that have been moved?

After the exclusion of the situation after the first time with a multimeter to measure the resistance between the circuit board and the ground is usually the resistance of the circuit board should not be less than 70Ω. If the resistance is too small, only a few or ten ohms.

Board components have been punctured or part of the breakdown must take measures to be broken down the components to find out the specific method is to be installed plate power (Note! At this time must be clear the board's operating voltage

The voltage value and the positive and negative polarity can not be connected to the wrong and add higher than the operating voltage. Otherwise, the repair circuit board will be hurt! Old fault did not rule out the new problems !!) With the temperature measured on the circuit board devices

Temperature, the temperature rise faster and higher as the key suspects. If the resistance is normal and then use a multimeter to measure the plate on the resistance of the device, the transistor and the stripper switch and other components.

The first thing to do is to make sure that the measured components are normal and do not complicate problems with general test tools such as multimeters.

Principle two: first inside and outside

If the situation allows a good circuit board to be used as a reference for the board, then use the tester's double-Bang VI curve scan function to perform good and bad tests on the two boards.

Comparison test points can start from the port of the circuit board; and then by the table and in particular the comparison test on the capacitor.This can make up the multimeter online difficult to measure whether the capacitor leakage leakage.

Principle three: the first easy after the difficult

In order to improve the test results in the circuit board on-line functional testing should be done before the panel to do some technical treatment to minimize the impact of various interference on the test process.Specific measures are as follows:

1. Preparation before testing

Will be short-circuit crystal (Note that the four feet of the crystal to find out that the two legs for the signal output pin can short-circuit the feet. Remember that the other case the other feet for the power pin must not be shorted !!) For large capacity

The capacitor should also be soldered to make it open, because the charge and discharge of large capacity capacitors will also bring interference.

2. Use the exclusion method to test the device

During the on-line test or comparative test of the device, the test results (eg, normal) are used to confirm the test results.

If you do not pass it, you can also confirm the test results. This has been tested until the device on the board is tested (or compared) and then processed by those who have not passed the test (or compare tolerance)

Devices that do not pass the function of the test device Some test instruments also provide a less formal but more practical approach: because the kind of test equipment on the circuit board can also be

The device is disengaged from the circuit board power supply system if the device is applied to the power supply pin of the device.

In this case, the device is tested for on-line function; since the other devices on the circuit board will not work to eliminate the interference effect. The actual test results at this time will be equivalent to "quasi-off-line test"

The quasi rate will be greatly improved.