Tait TM8000 Series Service Manual page 159

Task 3 —
All LEDs Faulty
Task 4 —
Display and All LEDs
Faulty
TM8100 Mobile Radio Service Manual
May 2004 © Tait Electronics Limited
If the display functions correctly but all the LEDs are faulty, repair the
control head as follows:
1. Disconnect the control-head loom.
2. Replace IC3 [at 1D5] which drives the switching transistors for
the LEDs. See
3. Reconnect the loom and test the user interface. If the fault has
been removed, return to
not, the repair failed; replace the control-head board as described
in Subsection 7.4 (on page
If the display is faulty as well as all the LEDs, repair the control head as
follows:
1. Use a multimeter to measure the 3.3 V DC supply voltage across
C1 [at 1D2] (see
not, go to Step 2.
2. Check for shorts to ground of the 3.3 V supply. Repair any fault
and go to Step 8.
3. Use the multimeter to check that the
IC7 is high. The level should be 3.3 V. If it is, go to Step 5. If it
is not, go to Step 4.
4. Check for continuity in the LCD driver circuitry (D22, C12,
R27) [at 1E9 and 1E10] (see
to Step 8. If there is no continuity fault, replace IC7 and go to
Step 8.
5. Use the multimeter to check that the
IC5 is low. The level should be less than 0.6 V. If it is, replace IC7
and go to Step 8. If it is not, go to Step 6.
6. Check that the voltage at pins 4, 10 and 14 of IC5 is 3.3 V DC.
Also check that pin 7 [at 1J8] of IC5 is at ground. If the voltages
are correct, replace IC7 and go to Step 8. If they are not, go to
Step 7.
7. Check for continuity between IC5 and the control-head
connector SK1. Also check for shorts to ground between IC5 and
SK1. Repair any fault and go to Step 8.
8. Confirm the removal of the fault, and return to
the repair failed or no fault could be found, replace the control-
head board as described in
Figure 7.3.
Subsection 5.2 (on page
163).
Figure 7.2). If it is correct, go to Step 3. If it is
RST
Figure 7.2). Repair any fault and go
Subsection
Servicing of Control Head
109). If it has
line at pin 6 [at 1E10] of
line at pin 8 [at 1F10] of
OE
Subsection 5.2. If
7.4.
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