Ericsson LBI-39175A manual Receiver, Pwb

LBI-39175A

SYMPTOM

Low RF sensitivity.

High audio distortion

RECEIVER

DIAGNOSTIC PROCEDURE

a.Program a Conventional System with frequencies given in Tables 2 and 3. Use "EDACS3" PC Programming utility.

b.Unscrew the PA module from the TXRX module. Disconnect the coaxial cable P2 from J401 on the Synthesizer PWB. 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. If this passes, replace the PA

PWB.

d.If this fails, re-align the receiver, as instructed in the "ALIGNMENT" section, and re-check the sensitivity at J401

e.If this passes, re-assemble with the PA module and re-check the sensitivity at the antenna connector. If this passes, the job is complete

f.If the above fails, substitute a known good Synthesizer PWB, and re-check the sensitivity. If this fails, replace the Logic PWB. Be sure to perform the complete re-programming on the new Logic PWB. If this passes, replace the synthesizer PWB, and re-load the Modulation Tracking Data.

a.Program a Conventional System with frequencies given in Tables 2 and 3. Use "EDACS3" PC Programming utility.

b.Apply a standard 1000 μV RF signal [with 1 kHz audio modulation at 3 kHz deviation (1.5 kHz for 12.5 kHz channel spacing)] 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 the audio distortion at the "VOL HI" output (J1003 Pin 13 referenced to Pin 12). If this passes (3% THD), replace IC604 Audio Power Amplifier on the Logic PWB.

d.If this fails, re-align the receiver per alignment procedure. Re-check the distortion at the speaker load or "VOL HI."

e.If this fails, replace the Logic PWB. If this passes, the job is finished.

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