Tait TM8000 Series Service Manual page 195

TM8100 Mobile Radio Service Manual
May 2004 © Tait Electronics Limited
4. The VCXO tank circuit (Q501, D501, D502, XL501 and
associated components) or the crystal XL501 [at 5D3/5E4] is
faulty (see Figure
board assembly from the chassis, and remove the
Locate and repair the fault, confirm the removal of the fault, and go
to Step 9. If the repair failed, return to
the complete main-board assembly.
5. There is a fault in the CODEC 2 circuitry or with the digital
signals to and from IC205 [at 2P2/2D12]. The CODEC 2
circuitry comprises IC205 and associated components under the
can (see
CDC TOP
2Q1/2C13] under the
Subsection 9.1). If not already done, remove the
6. Check the signals
2
at pin 12,
CDC
2Q2]. The signals should be active 3.3 V digital signals to and
from the digital board. If the signals are correct, go to Step 8. If
they are not, go to Step 7.
7. If any or all digital signals are missing, check the connections
between IC205 and the digital board. Repair any faults such as
open circuits, and return to Step 1. If the connections are not
faulty, then the digital board is faulty. Return to
and replace the complete main-board assembly.
8. The CODEC 2 circuitry identified in Step 5 is faulty. Locate and
repair the fault, confirm the removal of the fault, and go to Step
9. Note that, if the circuitry is functioning properly, probing the
501 test point [at 5F5/5G5] (see
TP
will show a five-step staircase signal followed by a random nine-
step staircase signal — this is the expected power-up auto-
calibration sequence. If the repair failed, return to
and replace the complete main-board assembly.
9. Replace all cans. Repeat Steps 1 to 3 to confirm the removal of
the fault. If the repair failed, return to
the complete main-board assembly.
9.12). If not already done, remove the main-
Figure 9.16 in Subsection
can (see
CDC BOT
2
at pin 10 of IC205,
DIG CDC LRCK
at pin 8, and
DIG SDTO
Figure
Diagnosis of Faults on Main Board
can.
VCXO BOT
Subsection 8.1 and replace
9.5) as well as R246 [at
Figure 9.3 of
can.
CDC TOP
2
DIG CDC
2
at pin 9 [at
DIG CDC SDTI
Subsection 8.1
9.11) during power-up
Subsection 8.1
Subsection 8.1 and replace
SCLK
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