TB7100 Service Manual Receiver Fault Finding 201
© Tait Electronics Limited October 2005
12 Receiver Fault Finding
Fault Conditions This section covers the diagnosis of faults in the receiver. The fault-diagnosis
procedures consist of 18 tasks grouped into the following sections.
The symptoms of the fault in the receiver circuitry determine which
sections 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” on
page 202 to determine the extent of the loss in sensitivity.
CCTM Commands The CCTM commands required are listed in Table 12.1. Full details of the
commands are given in “Computer-Controlled Test Mode (CCTM)” on
page 91.
Table 12.1 CCTM commands required for the diagnosis of faults in the receiver
Command Description
72
101 x y 0
376
378
Read 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 values
Read tuning voltage for front-end circuitry — displays voltage x in millivolts
Read signal power at output of channel filter — displays power x (square of amplitude)
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