202
Frequency Synthesizer Fault Finding
TM8100/TM8200 Service Manual
© Tait Electronics Limited
June 2006
Task 16 —
Check
TP
503 Test
Point
If the reference voltage, feedback voltage, and
DIG
SYN
FAST
line are all
correct, check the voltage at the
TP
503
test point.
1.
Measure the voltage at the
TP
503
test point
(see
).
The oscilloscope should show a DC level less than 3.0V with no sign
of noise or modulation.
2.
If the correct result is obtained, go to
. If it is not, go to
3.
The loop filter is faulty but the above measurements do not provide
more specific information. Check
IC504
,
IC505
,
Q511
(see
) and associated components.
4.
Check the following components (see
), then conclude
with
Note
On early issue boards,
C548
may be fitted instead of these
components.
5.
Remove
R566
and
R570
(see
), which provide a
modulation path to the VCO(s).
6.
Repeat the measurement of
.
7.
If the correct result is now obtained, go to
. If the correct result
is still not obtained, the CODEC and audio circuitry is suspect;
resolder
R566
and
R570
in position (see
“CODEC and Audio Fault Finding” on page 381
8.
Resolder
R566
and
R570
in position (see
9.
Check
IC504
(pins 6, 8, 9) (see
) and the associated
components in the loop filter.
10.
If a fault is found, repair the circuit, and confirm that the voltages are
now correct. If they are, go to
. If they are
not, or if no fault could be found, replace the board and go to
.
TP503 test point: < 3.0 V DC
A4 band:
C5085
to
C5089
B1 band:
C5085
to
C5089
C0 band:
C5085
to
C5088
D1 band:
C5085
to
C5088
H5 band:
C5085
and
C5086
H6 band:
C5085
and
C5086
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...
