TM8100/TM8200 Service Manual
Fault Finding of Control Head with 1- 2- or 3-Digit Display
433
© Tait Electronics Limited
June 2006
Control-Head Board
Faulty
If neither the elastomeric strips nor the LCD are faulty, check the relevant
components on the control-head board:
1.
Use an oscilloscope to display the signal at pin 5 of IC5
(see
). The signal should be a square wave with a fre-
quency of about 60Hz and an amplitude that alternates between 0.0
and 3.3V. If the signal is correct, go to
. If it is not, go to
.
2.
Replace IC2 (see
). Test the user interface. If the fault has
been removed, return to
. If it has not, go
to
3.
Use the oscilloscope to display the signal at pin 12 of IC7 (see
). The signal should be a square wave with a frequency of
about 120Hz and an amplitude that alternates between 0.0 and 3.3V.
If the signal is correct, replace IC5 and go to
. If it is not,
replace IC7 and go to
4.
Test the user interface. If the fault has been removed, return to
. If it has not, the repair failed; replace the
control-head board.
15.2
Some LEDs Faulty
If the display functions correctly but one or more (but not all) of the LEDs
D1 to D18 are faulty:
1.
Disconnect the control-head loom. Remove the control-head board.
Reconnect the loom to the board.
2.
Use a multimeter to measure the forward voltage across each faulty
LED. See
. The voltage should be 2.0±0.4V DC. If it is,
go to
. If it is not, replace the LED and go to
.
3.
If the forward voltage is correct, the LED is functional but the
associated switching transistor is suspect. Replace the transistor
corresponding to the LED in question. The switching transistors
associated with the LEDs D1 to D18 are Q1 to Q4. See
4.
Test the user interface. If the fault has been removed, re-assemble the
control-head board, and return to
. If it
has not, replace the control-head board and return to
.
Summary of Contents for TM8235
Page 1: ...TM8100 mobiles TM8200 mobiles Service Manual MMA 00005 04 Issue 4 June 2006...
Page 10: ...10 TM8100 TM8200 Service Manual Tait Electronics Limited June 2006...
Page 62: ...62 Description TM8100 TM8200 Service Manual Tait Electronics Limited June 2006...
Page 148: ...148 Disassembly and Reassembly TM8100 TM8200 Service Manual Tait Electronics Limited June 2006...
Page 162: ...162 Servicing Procedures TM8100 TM8200 Service Manual Tait Electronics Limited June 2006...
Page 178: ...178 Interface Fault Finding TM8100 TM8200 Service Manual Tait Electronics Limited June 2006...
Page 258: ...258 Receiver Fault Finding TM8100 TM8200 Service Manual Tait Electronics Limited June 2006...
Page 446: ...446 Spare Parts TM8100 TM8200 Service Manual Tait Electronics Limited June 2006...
