TM8100 Mobile Radio
Service Manual
Diagnosis of Faults on Main Board
191
May 2004 © Tait Electronics Limited
9.4
Frequency Control Loop
Lock Status
Fault diagnosis of the FCL is divided into four tasks. First discussed,
however, is the lock status of the radio, which will indicate whether or
not the FCL is suspect. The lock status might already have been
determined as part of the preliminary fault diagnosis. The following is a
summary:
1.
Enter the CCTM command
33
to place the radio in transmit
mode.
2.
Enter the CCTM command
72
to determine the lock status in
transmit mode. Note the response. The normal status is
110
.
3.
Enter the CCTM command
32
to place the radio in receive mode.
4.
Enter the CCTM command
72
to determine the lock status in
receive mode. Note the response. The normal status is
111
.
5.
If the lock status in either or both receive and transmit mode is
a
0
a
, where
a
is
0
or
1
, the FCL is suspect; proceed to Task 1.
Task 1 —
Check VCXO and
TCXO Outputs
First check the VCXO output and the TCXO output as follows:
1.
Use an oscilloscope probe to check the VCXO output at C536 [at
5G8/5H6] — probe the via situated between C536 and R537 (see
). The signal should be a sine wave of about 1.1 V
pp
on 1.45 V DC. If it is, go to Step 3. If it is not, go to Step 2.
2.
The VCXO circuitry (Q501, Q503, XL501 and associated
components) under the
VCXO
BOT
can is faulty. If not already done,
remove the main-board assembly from the chassis, and remove the
VCXO
BOT
can. Locate and repair the fault in the VCXO (see
). Confirm the removal of the fault and go to Step 3.
If the repair failed, return to
and replace the
complete main-board assembly.
3.
Use the oscilloscope probe to check the TCXO output at the
TP
504
test point [at 5B8/5J2] (see
). (The test point is
at the junction of C510 and R513.) The signal is
SYN
RX
OSC
and
should be a clipped sine wave of about 1.0 V
pp
. If it is, go to Task
2. If it is not, go to Step 4.
4.
The TCXO circuitry (XL500 [at 5B8/5J2] and associated
components) under the
CDC
TOP
can is faulty. Remove the
CDC
TOP
can. Locate and repair the fault in the TCXO (see
in
). Confirm the removal of the fault and go to Task
2. If the repair failed, return to
and replace the
complete main-board assembly.
Summary of Contents for TM8000 Series
Page 32: ...32 Introduction TM8100 Mobile Radio Service Manual May 2004 Tait Electronics Limited ...
Page 78: ...78 Circuit Descriptions TM8100 Mobile Radio Service Manual May 2004 Tait Electronics Limited ...
Page 106: ...106 General Information TM8100 Mobile Radio Service Manual May 2004 Tait Electronics Limited ...
Page 124: ...124 Servicing Procedure TM8100 Mobile Radio Service Manual May 2004 Tait Electronics Limited ...
