Regarding the maintenance principle of PCB circuit boards, the automatic soldering machine provides convenience for the soldering of PCB circuit boards, but problems often occur in the production process of PCB circuit boards, which will affect the quality of solder. In order to improve the test effect, some technical processing should be done on the repaired board before the online functional test of the PCB circuit board to minimize the influence of various interferences on the test process. The specific measures are as follows:
. Preparation before the test

Short-circuit the crystal oscillator (pay attention to the four-pin crystal oscillator to find out which two pins are the signal output pins and can short-circuit these two pins. Remember that the other two pins are the power pins under normal circumstances and must not be short-circuited!!) For large-capacity electrolytic The capacitor should also be soldered down to make it open. Because the charging and discharging of large-capacity capacitors will also cause interference.

2. Use the exclusion method to test the PCB circuit board of the device

During the online test or comparison test of the device, please directly confirm the test result and record the device that has passed the test (or is relatively normal). If the test fails (or is out of tolerance), it can be tested again. If it still fails, you can also confirm the test results first. This continues until the device on the board is tested (or compared). Then deal with those devices that fail the test (or are out of tolerance).

Some test instruments also provide a less formal but more practical processing method for devices that cannot pass the online test of the function: because the power supply of the test instrument to the circuit board can also be applied to the corresponding power supply and the corresponding power supply of the device through the test clip. If the power pin of the device is cut on the ground pin, the device will be disconnected from the power supply system of the circuit board.
At this time, perform an online functional test on the device; since other devices on the PCB will not be energized to work to eliminate the interference effect, the actual test effect at this time will be equivalent to the “quasi-offline test”. The accuracy rate will be very high. Great improvement.