TM9100 Service Manual Receiver Fault Finding 227© Tait Electronics Limited August 200510 Receiver Fault FindingFault Conditions This section covers the diagnosis of faults in the receiver. The fault-diagnosisprocedures consist of 18 tasks grouped into the following sections.The symptoms of the fault in the receiver circuitry determine whichsections are relevant:■ “Faulty Receiver Sensitivity”■ “Excessive Loss of Sensitivity”■ “Moderate or Slight Loss of Sensitivity”■ “Incorrect RSSI Readings”■ “Faulty Radio Mute”■ “High Receiver Distortion”If the receiver sensitivity is low, begin with “Faulty Receiver Sensitivity” onpage 228 to determine the extent of the loss in sensitivity.CCTM Commands The CCTM commands required are listed in Table 10.1. Full details of thecommands are given in “Computer-Controlled Test Mode (CCTM)” onpage 112.Table 10.1 CCTM commands required for the diagnosis of faults in the receiverCommand Description72101 x y 0376378Read lock status of RF PLL, FCL and LO2 — displays xyz (0=not in lock, 1=in lock)Set transmit frequency (x in hertz) and receive frequency (y in hertz) to specified valuesRead tuning voltage for front-end circuitry — displays voltage x in millivoltsRead signal power at output of channel filter — displays power x (square of amplitude)
