LBI-38908
18
RECEIVER
SYMPTOM DIAGNOSTIC PROCEDURE
Low RF sensitivity a) Program a Conventional System with frequencies given in Tables 2 or 3. Use
"EDACS3" PC programming utility.
b) Unscrew the PA module from the TXRX module. Disconnect coaxial cable P2 from
J401 on the Synthesizer board. Do not disconnect any other cable.
c) Set the frequency of the RF signal generator to the middle of the split. Apply a standard
RF signal to J401 and measure 12 dB SINAD sensitivity. Sensitivity should be better
than 0.29 µV.
d) If correct, replace the PA board.
e) If not, realign the receiver, as instructed in the "ALIGNMENT" section and recheck
sensitivity at J401.
f) If correct now, reassemble with the PA module and recheck sensitivity at the antenna
connector. If correct, the job is complete.
g) If not correct, substitute a known good Synthesizer board and recheck sensitivity.
h) If still not correct, replace the Logic board. Be sure to perform complete
reprogramming on the new logic board. If correct , replace the Synthesizer board and
reload Modulation Tracking Data.
High audio distortion a) Program a Conventional System with frequencies given in Tables 2 or 3. Use the
"EDACS3" PC programming utility.
b) Apply a standard 1000 µV RF signal (with 1 kHz audio modulation at 3 kHz deviation)
at one of the programmed RF frequencies in the center of the split to J1001. Set the
volume control to produce 15 watts at the 4 ohm speaker load.
c) Measure audio distortion at "VOL HI" output (J1003, Pin 13 referenced to Pin 12). If
correct (3% THD), replace IC604 Audio Power Amplifier on the Logic board.
d) If not, realign the receiver according to the alignment procedure. Recheck
distortion at the speaker load or "VOL HI".
e) If not correct, replace the Logic board. If correct, job is complete.
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