Tait TM8100 mobiles Service Manual page 207

Task 15 —
Check DIG SYN FAST
Line
TM8100/TM8200 Service Manual
© Tait Electronics Limited November 2007
If the loop filter is suspect but the reference and feedback voltages are
correct, check the
DIG SYN FAST
Enter the CCTM command 389 1 to set the synthesizer mode to fast.
1.
2. Measure the voltage at the collector of Q505 (see
The result should be:
Q505 collector: 14.2 ± 0.3V DC (after entry of CCTM 389 1)
B1 50W from board revision -04 and K5: 15.5V ± 0.3 DC
Enter the CCTM command 389 0 to set the mode to slow.
3.
4. Measure the voltage at the collector of Q505 (see
The result should be:
Q505 collector: 0V DC (after entry of CCTM 389 0)
5. If the voltages measured in
Task 16. If they are not, go to
6. Remove R105 (see
Enter the CCTM command 389 1 to set the mode to fast.
7.
8. Measure the voltage at the via between R105 and the digital board
(see Figure 9.7). The result should be:
via at R105: 0V DC (after entry of CCTM 389 1)
Enter the CCTM command 389 0 to set the mode to slow.
9.
10. Measure the voltage at the via between R105 and the digital board
(see Figure 9.7). The result should be:
via at R105: 3.3 ± 0.3V DC (after entry of CCTM 389 0)
11. If the voltages measured in
Step 12. If they are not, the digital board is faulty; replace the board
and go to "Final Tasks" on page
12. Check and resolder R105 in position (see
continuity between the collector of Q505 (see
digital board via R105.
13. 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 board and go to
Tasks" on page
line, which is input to the inverter.
Step 2 and
Step 6.
Figure 9.7).
Step 8 and
163.
"Final Tasks" on page
163.
Frequency Synthesizer Fault Finding
Figure 9.4).
Figure 9.4).
Step 4 are correct, go to
Step 10 are correct, go to
Figure 9.7), and check for
Figure 9.4) and the
163. If they are
"Final
207