Tait TM8100 mobiles Service Manual page 188

Task 2 —
Lock Status
188 Frequency Synthesizer Fault Finding
Enter the CCTM command 205 to reset the calibration values to the
6.
default values. Then enter the CCTM command 302 0 10 again to
calibrate the transmit VCO.
7. If the calibration succeeded, confirm the removal of the fault, and go
to "Final Tasks" on page
(UHF radios) or
8. Program the radio with the maximum frequency in the radio's
frequency band: Enter the CCTM command 101 x x 0, where x is the
frequency in hertz.
Enter the CCTM command 72 to determine the lock status in receive
9.
mode. Note the response.
lock status=xyz (x=RF PLL; y=FCL; z=LO2) (0=not in lock; 1=in lock)
If the lock status is 111 or 110, the synthesizer is functioning in the
10.
receive mode, and the power supplies and PLL are functioning
correctly. Go to
VCOs, and buffer amplifiers. If the lock status is 011 or 010, the
synthesizer is faulty in the receive mode. Go to
page 189.
A lock error indicates that the frequency synthesizer, FCL or second LO is
out of lock. To determine which is faulty, check the lock status as described
below.
1. If not already done, place the radio in CCTM.
2. Program the radio with the receive frequency of a channel that is
known to be out of lock: Enter the CCTM command 101 x x 0,
where x is the frequency in hertz.
Enter the CCTM command 72 to determine the lock status in receive
3.
mode. Note the response. The action required depends on the lock
status as described in the following steps.
lock status=xyz (x=RF PLL; y=FCL; z=LO2) (0=not in lock; 1=in lock)
If the lock status is x0x, where x is 0 or 1, the FCL is suspect; go to
4.
"Power Supply for FCL" on page
If the lock status is 011, the synthesizer is suspect, although the power
5.
supplies are functioning correctly; go to
6. If the lock status is 010, the synthesizer and second LO are both out
of lock. First investigate the synthesizer, excluding the power supplies;
go to "Loop Filter" on page
later.
163. If the calibration failed, go to
"Power Supplies" on page 189
"Loop Filter" on page 204
234.
204. If necessary, investigate the receiver
© Tait Electronics Limited November 2007
Step 8
(VHF radios).
to check the loop filter,
"Power Supplies" on
"Loop Filter" on page
TM8100/TM8200 Service Manual
204.