TM8100/TM8200 Service Manual Frequency Synthesizer Fault Finding 227© Tait Electronics Limited June 20069.8 Power Supply for FCLFault-DiagnosisStages Indications of a fault in the FCL will have been revealed by the initial checksin “Initial Checks” on page 180 and the PLL checks in “Phase-lockedLoop” on page 192. In the latter case a fault with the reference frequencyinput from the FCL to the PLL will imply that the FCL is suspect. Faultdiagnosis 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 andmeasurement points for diagnosing faults in the FCL are summarized inFigure 9.15.
