TB7100 Service Manual Frequency Synthesizer Fault Finding 189
© Tait Electronics Limited October 2005
11.8 Power Supply for FCL
Fault-Diagnosis
Stages
Indications of a fault in the FCL will have been revealed by the initial checks
in “Initial Checks” on page 144 and the PLL checks in “Phase-locked
Loop” on page 155. In the latter case a fault with the reference frequency
input from the FCL to the PLL will imply that the FCL is suspect. Fault
diagnosis of the FCL is divided into four stages:
■ check power supply
■ check VCXO and TCXO outputs
■ check signals at TP501 and TP502
■ check VCXO and CODEC circuitry
The checking of the power supply is given in this section in Task 34
below.
The remaining three stages are covered in “VCXO and TCXO Outputs”
to “VCXO and CODEC Circuitry” respectively. The test and
measurement points for diagnosing faults in the FCL are summarized in
Figure 11.14.
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