Failure phenomena |
Reason for failures |
Failure analysis and solutions |
1.One unit panel do not light |
1 .if +5V electricity or GND supply 2 .if +5V and GND are short circuit 3 .if the OE signals of 138 no. 5 leg exists 4 .if the OE signals which connected with 245 are normal (open circuit or short circuit) |
• supply +5V electricity or GND • cut the short-circuit part • supply OE signal . connect the open circuit part cut the short-circuit part |
2.One unit panel upper half or lower half do not light or display unnormally |
1 ¡¢if the 5 the leg of OE signal of 138 exists £» 2 ¡¢if the no. 11 and 12 leg signals of 74HC595 are normal(SCLK,RCK) £» 3 ¡¢if the connected OE signals are normal; £¨ open circuit or short circuit £© 4 ¡¢double row pins and the signal of SCLK ,RCK connected with 245 are normal £¨ open circuit or short circuit £© |
• connect OE signal • connect SCLK.RCK signal well • connect the open circuit part cut the short-circuit part • connect the open circuit part cut the short-circuit part |
3.One row of one unit panel or row of one corresponding module do not light or display unnormally |
1¡¢check if the pin of corresponding module row signal is cold welded or miss welding 2¡¢ check if the row signal and TIP127 or 4953 corresponding pins are cut off or short circuit with other signals 3¡¢check if the up-and-down pull resistance of row signal do not weld or miss welding 4¡¢ if the 74HC138 output row signal and corresponding TIP127 or 4953 are cut off or short circuit with other signals |
•Weld well for the cold welding and miss welding part • connect the open circuit part cut the short-circuit part • weld the not welding part, weld well of the miss welding part • connect well the open circuit part,cut the short circuit part |
4.One unit panel has two rows lighting at the same time £¨when displaying words, one row is normal, another row keeps lighting£© |
1¡¢check if the module corresponding two rows of signals are short circuit 2¡¢Check if the output leg of 138. up-and-down pull resistance and module pins and the output leg of TIP127 are shot circuit |
• cut the short circuit part • cut the short circuit part |
5.upper part or lower part, red or green don't light or not display normally |
1.check if the input row niddle feet are normal or short circuit with GND.+5V 2.check if the signals from input row niddles to 245 are normal£¨short circuit or open circuit£© 3.IC245 is broken |
• connect the open circuit part • cut the short-circuit part • change IC |