Pcb Layout Of The Keypad Backlighting Circuitry - Tait TM9100 Service Manual

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Figure 14.8

PCB layout of the keypad backlighting circuitry

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TM9100 Service Manual
© Tait Electronics Limited August 2005
With the intensity set to high, check the signals at pins 2 (B1) and 5
(B2) of Q2.
Q2 pin 2 (B1): GND
Q2 pin 5 (B2): GND
If any of these signals are incorrect, the FPGA is faulty and the con-
trol-head board must be replaced.
Check the signals at pins 6 (C1) and 3 (C2) of Q2. Check the signals
at pins 1 (E1) and 4 (E2) of Q2.
Q2 pin 6 (C1): 3.3V
Q2 pin 3 (C2): 3.3V
Q2 pin 1 (E1): 3.3V
Q2 pin 4 (E2): 3.3V
If any of these signals are incorrect, Q2 is faulty.
Check the resistors R607, 611, and R613 for shorted or open
circuits.
R607: 3.3kΩ
R611: 2.2kΩ
R613: 1kΩ
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Fault Finding of Control Head 409