Tait TB7100, Service Manual

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192 Frequency Synthesizer Fault Finding TB7100 Service Manual
© Tait Electronics Limited October 2005
11.9 VCXO and TCXO Outputs
Task 35 —
VCXO Output
If the 3V power supply is not faulty, check the VCXO output as follows:
1. Use an oscilloscope probe to check the VCXO output at C536 —
probe the via next to C536 (see
Figure 11.16 ). The signal should be:
2. If the signal is correct, go to Task 36 . If it is not, go to Step 3 .
3. The VCXO circuitry under the
VCXO BOT
can is faulty. Remove the
VCXO BOT
can.
4. Locate and repair the fault in the VCXO (Q501, Q503, XL501 and
associated components) (see
Figure 11.17 ).
5. Confirm the removal of the fault and go to Task 36 . If the repair
failed, replace the main-board assembly and go to “Final Tasks” on
page 123 .
VCXO output at C536: sine wave of 1.1
±
0.2 V
pp
on 1.4
±
0.2 V DC