Tait TM8100 mobiles, Service Manual

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TM8100/TM8200 Service Manual Fault Finding of Control Head with Graphical Display 429
© Tait Electronics Limited November 2007
2. Check the 3.3V supply voltage at pin 2 of the LCD connector J102.
If the signal is not correct, refer to “Power Supply Faulty” on
page 426 .
Tip
For a quick check of the LCD without having to disassemble the
control head, connect a good LCD to the control head, or discon-
nect the LCD loom and connect it to a good control head.
3. Replace the LCD. Carefully remove the protective plastic film from
the LCD. Take care not to scratch the soft polarizer material on the
top side of the LCD.
4. Use an oscilloscope to check the signals of pins 3 to 7 of connector
J102.
If any of the signals are missing or distorted, remove can E100 and
check for continuity between the FPGA and the LCD connector.
If necessary, replace the corresponding 100
Ω
resistor(s) R4 to R8.
J102 pin 2: 3.3V
J102 pins 3 to 7: The signals should be switching 0 to 3.3V in bursts of
0.125ms at approximately 1s intervals.
Figure 14.4 PCB layout of the LCD circuitry
top side