Judgment must be the primary mode of treatment after the second , the obvious first deal with serious , minor problems post-processing. Short circuit should be the highest priority.
1, the resistance detection method, the multimeter transferred resistance profile , detecting a normal circuit board to a point of resistance to ground , and then another piece of the same test on the same circuit board test point of the normal resistance value is different , if the difference to determine the extent of the problem .
2, the voltage detection method, the multimeter transferred voltage profile, detecting the suspected a certain point in the circuit to the ground voltage, the comparator is similar to the normal , or to determine the extent of the problem .
3, the short-circuit detection method, the multimeter transferred to short-circuit detection block ( some resistance diode drop file or files , usually with alarm function ) to detect whether there is a short circuit phenomenon and found that priority should be resolved after a short circuit , so as not to burn other devices . The law must be the case of power failure in the circuit operation , to avoid damage to the table .
4, the voltage drop detection method, transferred to the multimeter diode drop test file , because all of the IC are many single element from the basic composition , but small , so when it 's a pin on a current is passed , will be in the presence of voltage on pin drop . Generally the same type of IC pin drop on the same similarity , according to the pin drop on the value comparison is good or bad , must circuits case of power failure operation. This method has some limitations, such as the detection devices are high impedance , it is undetectable . Fourth, the cell plate processing steps FAQs unit board failure:
A. The entire board is not lit
1, check the power supply and signal cable is connected .
2, check whether the test card to identify interfaces, test card is not recognized red light flashing , check the light board whether the test card with the power ground , or light board interfaces between signal and ground short circuit causes not recognize interface. ( Intelligent Test Card )
3, the detection circuit 74HC245 whether the Weld , 245 corresponding enable (EN) signal input and output pins are soldered or shorted to other lines . NOTE : The main power supply and check Enable (EN) signal.
B. In the point-slope scan, regularity overlapping interlaced display does not light
1, check the A, B, C, D between the signal input port to 245 are plugged or soldered , short-circuit .
2, detection 245 corresponds to A, B, C, D between the output terminal 138 is open or Weld, shorted.
3 , test A, B, C, D each signal or a short circuit between the signal and ground circuit . Note: The main testing line ABCD signaling .
C. all bright line or lines when not lit
1, the detection 138-4953 between Weld line is open or short circuit .
D. scanning line , two lines or lines ( usually a multiple of 2 , with regularity ) simultaneously lit
1 , test A, B, C, D short circuit between the respective signals .
2 , detect whether the 4953 output with other output short circuit.
E. all lit with a single or multi-point ( irregular ) does not shine