Tait TB7100, Service Manual

Page: 192 / 370

194 Frequency Synthesizer Fault Finding TB7100 Service Manual
© Tait Electronics Limited October 2005
Task 36 —
TCXO Output
If the VCXO output is correct, check the TCXO output as follows:
1. Use the oscilloscope probe to check the TCXO output at the
TP
504
test point (see Figure 11.16 ). The signal is
SYN RX OSC
and should
be:
2. If the signal is correct, go to “Signals at TP501 and TP502” on
page 195 . If it is not, go to Step 3 .
3. The TCXO circuitry under the
CDC TOP
can is faulty. Remove the
CDC TOP
can.
4. Locate and repair the fault in the TCXO (XL500 and associated
components) (see
Figure 11.15 ).
5. Confirm the removal of the fault and go to “Signals at TP501 and
TP502” on page 195 . If the repair failed, replace the main-board
assembly and go to “Final Tasks” on page 123 .
TCXO output at TP504 test point: clipped sine wave of 1.0
±
0.2 V
pp
Figure 11.17 FCL circuitry under the VCXO BOT can
SYN BOT CAN
CDC BOT CAN
CAN FOR
DIGITAL
BOARD