Tait TM8000 Series User Manual

158 Servicing of Control Head TM8100 Mobile Radio Service Manual
May 2004 © Tait Electronics Limited
Task 1 —
Display Faulty but not
LEDs
If the checks in Subsection 7.1 (on page 151) show that neither the LCD
nor the elastomeric strips are faulty, check the relevant components on
the control-head board as follows:
1. Use an oscilloscope to display the signal at pin 5 [at 1H10] of IC5
(see Figure 7.3). The signal should be a square wave with a
frequency of about 60 Hz and an amplitude that alternates
between 0.0 and 3.3 V. If the signal is correct, go to Step 3. If it
is not, go to Step 2.
2. Replace IC2 [at 1G12] (see Figure 7.3). Test the user interface.
If the fault has been removed, return to Subsection 5.2
(on page 109). If it has not, go to Step 3.
3. Use the oscilloscope to display the signal at pin 12 [at 1H9] of IC7
(see Figure 7.3). The signal should be a square wave with a
frequency of about 120 Hz and an amplitude that alternates
between 0.0 and 3.3 V. If the signal is correct, replace IC5 and go
to Step 4. If it is not, replace IC7 and go to Step 4.
4. Test the user interface. If the fault has been removed, return to
Subsection 5.2. If it has not, the repair failed; replace the control-
head board as described in Subsection 7.4 (on page 163).
Task 2 —
Some LEDs Faulty
If the display functions correctly but one or more (but not all) of the
LEDs D1 to D18 are faulty, check the control-head board as follows:
1. Disconnect the control-head loom. Remove the control-head
board as described in Subsection 6.2 (on page 131). Reconnect
the loom to the board.
2. Use a multimeter to measure the forward voltage across each faulty
LED. See Figure 7.1. The voltage should be 2.0 ± 0.4 V DC. If
it is, go to Step 3. If it is not, replace the LED and go to Step 4.
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
Figure 7.3. Continue with Step 4.
4. Test the user interface. If the fault has been removed, re-install the
control-head board as described in Subsection 6.5 (on page 148),
and return to Subsection 5.2. If it has not, the repair failed;
replace the control-head board as described in Subsection 7.4.

Tait TM8000 Series Specifications

General

Brand	Tait
Model	TM8000 Series
Category	Radio
Language	English