Machine Disassembly/Assembly and Troubleshooting 
4-17 
Cannot start
Check if the AC indicator
 is lit
Check the keypad-to-main board signal line for fault;
Check the keypad-to-power board signal line for fault;
Check the keyboard for fault
Check the main board for fault;
Check the power board for fault;
Check/replace the 
above units one by one 
so as to locate the 
fault;
Check if the power 
supply is normal
Y N
Check the AC power 
cord is norma
l
Y
Check the keypad-to-power board signal 
line for fault; 
Check the keyboard for fault
Check the main board for fault;
Check the power board for fault;
Y
Check if battery is 
installed;
Check if the battery 
has electricity;
N
Y
Y
N
N
N
end
 
 
Figure 25 Black Screen Troubleshooting Map  
4.3.2 LCD Black, Backlight Off  
1.  Check if the LCD signal line is in good condition; 
2.  Check if the keypad power cord is in good condition;   
3.  If the problem still remains after the connection cables are replaced, replace the       
LCD module: 
4.  If the problem still exists, check the keypad, power board or main board. 
4.3.3 LED Displays Abnormally 
1.  Check if the LED signal line is in good condition; 
2.  Check if the keypad power cord is in good condition; 
3.  Check if the button signal line is in good condition; 
4.  If the problem still exists, check the keypad, power board or main board. 
4.3.4 Alarms Soundless 
1.  Check if the sound is turned off in the software setup;