Tait TP9100, Service Manual, Page: 161 / 326

TP9100 Service Manual
Frequency Synthesizer Fault Finding 161
© Tait Electronics Limited May 2005
Task 1 —
System Error
A system error indicates a fault in the calibration of either the FCL or the
frequency synthesizer. To determine which is faulty, calibrate the VCXO
and the transmit VCO as described below. (Always calibrate the former first,
because the latter depends on the former.)
1. Place the radio in CCTM.
2. Enter the CCTM command 301 0 10 to calibrate the VCXO.
The response will be one of the following three messages:
■
“passed sanity check. Cal’d values put into effect”
■
“failed sanity check. Cal’d values not in effect”
■
“Cal failed: lock error”
The first two messages will be preceded by four calibration values.
3. In the case of the first message (passed), go to Step 4 . In the case of
the second and third messages (failed), the FCL is suspect; go to
“Power Supply for FCL” on page 205 .
4. Enter the CCTM command
302 0 10
to calibrate the transmit VCO.
The response will be one of the three messages listed in Step 2 .
The first two messages will be preceded by eight calibration values.
Reset the radio and re-enter CCTM.
5. If the calibration succeeded but the system error persists, replace the
main board, and go to
“Final Tasks” on page 134 . In the case of the
second message (failed sanity check), go to Step 6 . In the case of the
third message (calibration failed), go to Step 8 (UHF radios) or
“Power Supplies” on page 163 (VHF radios).
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 134 . If the calibration failed, go to Step 8
(UHF radios) or “Power Supplies” on page 163 (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 176 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 163 .
lock status=
xyz
(
x
=RF PLL;
y
=FCL;
z
=LO2) (0=not in lock; 1=in lock)