Ericsson LBI-38505A Maintenance Manual
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Ericsson LBI-38505A Maintenance Manual

Ericsson LBI-38505A Maintenance Manual

Base station 406-512 mhz receiver
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LBI-38505A
(Supercedes LBI-30025)
Maintenance Manual
MASTR
II
®
BASE STATION
406-512 MHz RECEIVER
TABLE OF CONTENTS
RF ASSEMBLY, MIXER AND
REFILTER BOARD . . . . . . . . . . . . . LBI-30032
(DF1107)
OSCILLATOR/MULTIPLIER
BOARD . . . . . . . . . . . . . . . . . . . . LBI-30029
(DF1106)
IF AUDIO AND SQUELCH
BOARD . . . . . . . . . . . . . . . . . . . . LBI-38507
Ericsson Inc.
Private Radio Systems
Mountain View Road
Lynchburg, Virginia 24502
1-800-528-7711 (Outside USA, 804-528-7711)
Printed in U.S.A.

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Summary of Contents for Ericsson LBI-38505A

  • Page 1 LBI-38505A (Supercedes LBI-30025) Maintenance Manual MASTR ® BASE STATION 406-512 MHz RECEIVER TABLE OF CONTENTS RF ASSEMBLY, MIXER AND REFILTER BOARD ... . . LBI-30032 (DF1107) OSCILLATOR/MULTIPLIER BOARD ....LBI-30029...

  • Page 2: Table Of Contents

    0.25 V SELECTIVITY EIA Two-Signal Method (25 kHz Spacing) -90 dB Spurious Response -90 dB Intermodulation (EIA) -75 dB Copyright © May 1990, Ericsson GE Mobile Communications Inc. Squelch Sensitivity Critical Squelch Page Maximum Squelch Frequency Stability 2C-ICOMs Modulation Acceptance...

  • Page 3: Figure 1 - Disassembly Procedure (Top View)

    Pull the locking handle down, then pry up the top cover at the front notch and lift off the cover. To service the Receiver from the bottom: Pull the locking handle down and pull the radio out of the mounting frame. NOTE...

  • Page 4: Figure 3 - Disassembly Procedure (Bottom View)

    LBI-38505 To remove the IF Filter board from the radio: Remove the eight screws (E) holding the IF Filter bottom cover. Remove the six screws (F) holding the IF Filter top cover. Remove the three screws (G) and the Connector (H), and carefully push down on the top of the board to avoid damaging the feedthrough capacitors.

  • Page 5: Figure 6 - Test Setup For 20 Hz Double-Trace Sweep Alignment

    LBI-38505 FRONT END ALIGNMENT EQUIPMENT REQUIRED Test Set Models 4EX3A11, 4EX8K12, or 20,000 ohms-per-Volt multimeter with a 1 Volt scale. A 406-512 MHz signal source. PRELIMINARY CHECKS AND ADJUSTMENTS Connect black plug from Test Set to Receiver Centralized Metering Jack J601, and red plug to system board metering jack J905. Set meter sensitivity switch to the TEST 1 position (or 1-Volt position on 4EX8K12).

  • Page 6: Oscillator/Multiplier Board

    VTVM at P904-3 or J601-2 on the IFAS board) is inadequate for oscillator frequency setting. If the radio is at an ambient temperature of 26.5°C (79.8°F), set the oscillator for the correct mixer frequency (ICOM FREQ. X 9).

  • Page 7: Complete Receiver Alignment

    The mixer and IF circuits have been aligned at the factory and will normally require no further adjustment. If adjustment is necessary, use the procedure out- lined in STEP 13. Refer to DATAFILE BULLETIN 1000-6 (IF Alignment of Two-Way Radio FM Receivers) for helpful suggestions on how to determine when IF Alignment is required.

  • Page 8: Test Procedures

    LBI-38505 Once the defective stage is pin-pointed, refer to the "Service TEST PROCEDURES Check" listed to correct the problem. Additional corrective meas- ures are included in the Troubleshooting Procedure. Before These Test Procedures are designed to help you to service a starting with the Receiver Test Procedures, be sure the receiver receiver that is operating---but not properly.

  • Page 9: Modulation Acceptance Bandwidth (If Bandwidth)

    LBI-38505 TEST PROCEDURES TEST PROCEDURES STEP 2 USABLE SENSITIVITY (12 dB SINAD) If STEP 1 checks out properly, measure the receiver sensitivity as follows: Apply a 1000 microvolt, on frequency signal modulated by 1000 Hz with 3.0 kHz deviation to A301-J1. With Function Switch on Distortion Analyzer set to VOLTMETER position, adjust volume control for 1.0 Watt (2.83 VRMS across 8 ohm load).
  • Page 10 TROUBLESHOOTING PROCEDURES LBI-38505 SYMPTOM CHECKS Con’t. SYMPTOM IMPROPER SQUELCH OPERATION Check voltages on Schematic Diagram. Make gain and waveform checks with noise. Make gain and waveform checks with 6 kHz signal. Check discrete components in the squelch circuit. Replace IC circuit U603. LOW OR DISTORTED AUDIO Check voltages on Schematic Diagram.
  • Page 11 TROUBLESHOOTING PROCEDURES LBI-38505 LBI-38505 406-512 MHz MASTR II RECEIVER...
  • Page 12 TROUBLESHOOTING PROCEDURES LBI-38505 LBI-38505 406-512 MHz MASTR II RECEIVER...

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