Tait TM8100 mobiles Service Manual page 202

Task 10 —
Line
SYN LOCK
202 Frequency Synthesizer Fault Finding
If all the critical inputs to the PLL are correct, check the
output.
Enter the CCTM command 72 to determine the lock status in receive
1.
mode. Note the status.
lock status=xyz (x=RF PLL; y=FCL; z=LO2) (0=not in lock; 1=in lock)
2. Check the
SYN LOCK
(see Figure 9.2). The voltage should depend on the lock status as
follows:
lock status 111 or 110: 3.0 ± 0.3V DC at pin 14 of IC503
lock status 011 or 010: 0V DC at pin 14 of IC503
3. If the voltage measured in
page 204. If it is not, go to
4. Check for continuity between pin 14 of IC503 and the digital board
via R568 (see Figure
5. If there is a fault, go to
faulty; replace the board and go to
6. Repair the fault. Confirm the removal of the fault and go to
Tasks" on page
replace the board and go to
line by measuring the voltage at pin 14 of IC503
Step 2 is correct, go to
Step 4.
9.2) and L102 (see
Step 6. If there is no fault, the digital board is
"Final Tasks" on page
163. If the repair failed or no fault could be found,
"Final Tasks" on page
© Tait Electronics Limited November 2007
line
SYN LOCK
"Loop Filter" on
Figure 9.7).
163.
"Final
163.
TM8100/TM8200 Service Manual