Check Tp503 Test Point - Tait TM9100 Service Manual

If the reference voltage, feedback voltage, and
Task 16 —
Check 503 Test
TP
correct, check the voltage at the
Point
1.
2.
3.
4.
5.
6.
7.
8.
9.
TM9100 Service Manual
© Tait Electronics Limited August 2005
Measure the voltage at the
The oscilloscope should show a DC level less than 3.0V with no sign
of noise or modulation.
TP503 test point: < 3.0 V DC
If the correct result is obtained, go to
The loop filter is faulty but the above measurements do not provide
more specific information. Check IC504, IC505, Q511
(see Figure 9.4), C5085 to C5089 (B1 band, see
C5085 and C5086 (H5, H6 bands see
components. Conclude with
Remove R566 and R570 (see
modulation path to the VCO(s).
Repeat the measurement of
If the correct result is now obtained, go to
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
Resolder R566 and R570 in position (see
Check IC504 (pins 6, 8, 9) (see
components in the loop filter.
If a fault is found, repair the circuit, and confirm that the voltages are
now correct. If they are, go to
not, or if no fault could be found, replace the main-board assembly
and go to "Final Tasks" on page
DIG SYN FAST
503 test point.
TP
503 test point (see
Figure
TP
Step 3. If it is not, go to
Figure
Figure 9.7), and associated
Step 9.
Figure 9.7), which provide a
Step 1.
Step 7. If the correct result
Figure 9.7), and go to
371.
Figure
Figure 9.4) and the associated
"Final Tasks" on page
147.
Frequency Synthesizer Fault Finding
line are all
9.7).
Step 4.
9.7) or
9.7).
147. If they are
191