User Guide

After Sales
Technical Documentation
THA–4S
Troubleshooting Guide
Page 11
Original, 12/95
Display / Keyboard Fault
N
Y
Y
Display 0k
Display/Keyboard
fault
N
Y
Y
Y
Y
N
N
N
Display OK?
Change display
module
Check
–soldering X400
–X400/pin5 Vbat
–X400/pin12 VL2
–X400/pin 16 –V –2.1V
–X400/pin 14 GND
–X400/pin7 LCD_Clock 280kHz
Lights OK?
Keypad foil
OK?
D101/pin 44
4.85V with
light on
Check
loading of lights line
If OK change D101
Check
–Switch V414, V419,
–V415
Check
–Short circuits in the keyboard layout
–Col 0–2 = 0V when no key is pressed
Change Keyboard
foil