182 Frequency Synthesizer Fault Finding TM8100/TM8200 Service Manual
© Tait Electronics Limited June 2006
6. Enter the CCTM command 205 to reset the calibration values to the
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 157. If the calibration failed, go to Step 8
(UHF radios) or “Power Supplies” on page 183 (VHF radios).
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.
9. Enter the CCTM command 72 to determine the lock status in receive
mode. Note the response.
10. If the lock status is 111 or 110, the synthesizer is functioning in the
receive mode, and the power supplies and PLL are functioning
correctly. Go to “Loop Filter” on page 198 to check the loop filter,
VCOs, and buffer amplifiers. If the lock status is 011 or 010, the
synthesizer is faulty in the receive mode. Go to “Power Supplies” on
page 183.
Task 2 —
Lock Status
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.
3. Enter the CCTM command 72 to determine the lock status in receive
mode. Note the response. The action required depends on the lock
status as described in the following steps.
4. If the lock status is x0x, where x is 0 or 1, the FCL is suspect; go to
“Power Supply for FCL” on page 227.
5. If the lock status is 011, the synthesizer is suspect, although the power
supplies are functioning correctly; go to “Loop Filter” on page 198.
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 198. If necessary, investigate the receiver
later.
lock status=xyz (x=RF PLL; y=FCL; z=LO2) (0=not in lock; 1=in lock)
lock status=xyz (x=RF PLL; y=FCL; z=LO2) (0=not in lock; 1=in lock)
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