TM8100/TM8200 Service Manual
Frequency Synthesizer Fault Finding
213
© Tait Electronics Limited
June 2006
Task 23 —
Check Transmit VCO
Check that the correct transmit frequency is synthesized. This is the
frequency of the transmit VCO output
SYN
TX
LO
at the
TX
port shown in
.
1.
Enter the CCTM command
335 1
to set the transmit-receive switch
on (transmit mode).
2.
Using a frequency counter, proceed as follows to observe the transmit
frequency at the
TX
port before and after grounding the junction
between
C541
and
R547
(see
While holding the probe from the counter on the
TX
port, use a pair
of tweezers to momentarily ground the junction. The frequency
should change to:
The loop filter will hold its output steady at 13.3 V. This should result
in a frequency equal to the maximum given in
3.
If the transmit frequency measured in
is correct, go to
If it is incorrect, go to
. If no frequency is detected, go to
4.
Proceed as follows to observe the transmit frequency at the
TX
port
before and after applying 3 V DC to the junction of
C541
and
R547
;
there is a convenient 3 V level at
R544
(see
While holding the probe on the
TX
port, use the tweezers to
momentarily apply 3 V DC to the junction; do not touch the board
with your hand, and do not allow the tweezers to touch any cans
when you remove them. The frequency should change to:
The loop filter will hold its output steady at about 0V. This should
result in a frequency equal to the minimum given in
5.
If the transmit frequency measured in
If it is incorrect, go to
. If no frequency is detected, go to
TX port: maximum transmit frequency (see
TX port: minimum transmit frequency (see
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...
