Ericsson LBI-38505A User Manual

LBI-38505A

(Supercedes LBI-30025)

Maintenance Manual

MASTR

BASE STATION 406-512 MHz RECEIVER

ericssonz

TABLE OF CONTENTS

RF ASSEMBLY, MIXE R AND

REFILTER BOARD . . . . . . . . . . . . . LBI-30032

(DF1107) OSCILLATOR/MULTIPLIER

BOARD . . . . . . . . . . . . . . . . . . . . LBI-30029

(DF1106) IF AUDI O AND SQUELCH

BOARD . . . . . . . . . . . . . . . . . . . . LBI-38507

Ericsson Inc.

Private Radio Systems Mountain V ie w Roa d Lynchbur g, V ir ginia 24502 1-800-528-7711 (Outside USA, 804-528-7711) Printed in U.S.A.

LBI-38505 LBI-38505

TABLE OF CONTENTS

Page

SPECIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

MAINTENANCE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

MODIFICATION INSTRUCTIONS (High Side Injection) . . . . . . . . . . . . . . . . . . . . . . . . 3

FRONT END ALIGNMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

ICOM FREQUENCY ADJUSTMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

COMPLETE RECEIVER ALIGNMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

TEST PROCEDURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Audio Power Output And Distortion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Usable Sensitivity (12 dB Sinad) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Modulation Acceptance Bandwidth (IF Bandwidth) . . . . . . . . . . . . . . . . . . . . . . . . . 8

TROUBLESHOOTING PROCEDURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

ILLUSTRATIONS

FIGURE 1 - DISASSEMBLY PROCEDURE (Top View) . . . . . . . . . . . . . . . . . . . . . . . . 2

Squelch Sensitivity

Critical Squelch Maximum Squelch

Frequency Stability

2C-ICOMs

Modulation Acceptance

Maximum Frequency Separation

406-470 MHz 470-494 MHz 1.50 MHz 2.0 MHz 494-512 MHz 1.50 MHz 2.0 MHz

Frequency Response

RF Input Impedance

*These specifications are intended primarily for the use of the serviceman. Refer to the appropriate Specifica tion Sheet for

the complete specifications.

Full Specifications 3 dB Degradation

1.60 MHz 2.0 MHz

Within +2 and -8 dB of a sta nd ard 6 dB per oc ta v e de-e mp has is cur v e fro m 300 t o 3000 Hz (1000 Hz reference)

50 ohms

0.25 µV0.1 Greater than 12 dB NQ (less than 1.0 µV)

0.0002% (-40°C to +70°C)

7 kHz (narrow-band)

FIGURE 2 - RECEIVER BLOCK DIAGRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

FIGURE 3 - DISASSEMBLY PROCEDURE (Bottom View) . . . . . . . . . . . . . . . . . . . . . . . 3

FIGURE 4 - RECEIVER MODULE LOCATION DIAGRAM . . . . . . . . . . . . . . . . . . . . . . 3

FIGURE 5 - TEST POINTS AND ALIGNMENT CONTROLS . . . . . . . . . . . . . . . . . . . . . . 4

FIGURE 6 - TEST SETUP FOR 20 Hz DOUBLE-TRACE SWEEP ALIGNMENT . . . . . . . . . . . . . . 4

FIGURE 7 - FREQUENCY CHARACTERISTICS vs. TEMPERATURE . . . . . . . . . . . . . . . . . . 5

SPECIFICATIONS*

Audio Output (to 8-ohm Speaker) 1 Watt at less than 3% distortion

Sensitivity

12 dB SINAD (EIA Method) 20 dB Quieting Method

SELECTIVITY

EIA Two-Signal Method (2 5 k H z Spacing) -90 dB -90 dB

Spurious Res po ns e -90 dB -100 dB

With Pre-Ampl Without Pre-Ampl

0.20 µV0.35

0.25 µV0.50

WARNING

Although the highest DC voltage in MASTR II receiv er is +12 Volts DC, high current may be drawn under short circuit conditions. These currents can possibly heat metal objects such as tools, rings, watc hbands, etc., enough to cause burns. Be careful when working near energized circuits!

High-level RF ener gy in the transmitte r Power Amplifier assembly can cause RF b u rns upon contact. Keep away from these circuits when the transmitter is energized!

Intermodulation (EIA) -75 dB -80 dB

LBI-38505 LBI-38505

DESCRIPTION

MASTR II Base Station, 40 6 to 512 mega hertz receivers are single con version, superheter odyne FM receiv ers designed for one-through eight-frequency operation. The solid state receiver utilizes integrated circuits (ICs), monolithic crystal filters and discrete components with each of the crystal filters located between gain stages to provide 100 dB selecti vity a nd maximum protection from de-sensitization and intermodulation.

The receiver consists of the following modules:

•

RF Assembly (Includes Mixer)

•

IF-Filter

•

Oscillator/Multiplier (Osc/Mult)

•

IF/Audio and Squelch (IFAS)

•

Optional Ultra-High Sensitivity

(UHS) Pre-Amplifier

Audio, supply voltages and control functions are connected to the system board through P903 on the Osc/Mult board, and P904 on the IFAS board. The regulated +10 Volts is used for all receiver stages except the audio PA stage which operates from the A+ system su pp ly.

Centralized metering jack J601 on the IFAS board is provided for use with Test Set 4EX3A11 or Test Kit 4EX8K12. The test set meters the oscillator, multiplier, IF Detector and IF amplifier stages. Speaker high and low are metered on the system board metering jack.

Remove the top cover , then loosen the two bottom co ver retaining screws and remove the bottom cover (see Figure 1).

3. To gain access to the bottom of the Osc/Mult and IFAS board, remove the six screws (A) holding the receiver bottom cover (see Figure 3).

NOTE

Refer to Figure 4 for receiver module location.

To remove the OSC/Mult board from the radio:

1. Remove the six screws (A) holding the receiver bottom cover.

2. Remove the eight screws (E ) holding the IF-Filter bottom cover .

3. Remove the four screws (B) holding the board.

4. Press strai ght down on the plug-in Osc/Mu lt boar d from the top to avoid bending the pins when unplugging th e board from the syste m bo ard jack.

To remove the IFAS board from the radio:

1. Remove the six screws (A) holding the bottom cover, and the one screw (C) holding the board.

A block diagram of the complete receiver is shown in

Figure 2.

Refer to the appropriate Maintenance Ma nual for complete

details on each receiver module listed in the Table of Contents.

MAINTENANCE

DISASSEMBL Y

To service the Receiver from the top (see Mechanical Parts Breakdown):

1. 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:

1. Pull the locking handle down and pull the radio out of the mounting frame.

2. Remove the two screws (D) holding the audio PA heatsink to the right side rail.

Figure 2 - Receiver Block Diagram

Figure 1 - Disassembly Procedure

(T op V iew)

LBI-38505 LBI-38505

MODIFICATION INSTRUCTIONS

Figure 3 - Disassembly Procedure

(Bottom Vi ew)

To remove the IF Filter board from the radio:

1. Remove the eight screws (E) holding the IF Filter bottom cover.

2. Remove the six screws (F) holding the IF Filter top cover.

3. Remove the thre e screws (G) and the Con nector (H), an d carefully push down on the top of the board to avoid damaging the feedthrough capacitors .

To remove the optional UHS pre-amplifier board:

1. Remove the eight screws (E) holding the IF Filter bottom cover , and the six screws (F) holding the IF Filter top cover.

2. Disconnect the two connectors and 10 Volt lead (J).

3. Remove the three screws on the bottom side of the board, and lift out the board.

MODIFICATION INSTRUCTIONS FOR UHF HIGH SIDE INJECTION APPLYING 19A130045G5 KIT. THIS MODIFICATION IS NOT REQUIRED FOR RECEIVERS OPERATING IN THE FOLLOWING RANGES.

450 TO 458.8 MHz 470 TO 482.8 MHz 494 TO 500.8 MHz

1. FOR RECEIVERS OPER ATING BETWEEN 458.8 TO 470 MHz (OSC/MULT BD’S 19D423266G2 & G6): A. IF THE RECEIVER HAS LESS THAN 8 ICOMS, REMOVE C407, C412, C417 .

REPLACE C407 WITH C2315 (13 pF, -N80). REPLACE C412 WITH C2316 (5pF, NPO).

B. IF THE RECEIVER HAS MORE THAN 8 ICOMS, REMO VE C407 , C41 2, C417 .

REPLACE C407 WITH C2317 (8pF, N80). REPLACE C412 WITH 2316 (5pF, NPO)

2. FOR RECEIVERS OPER ATING BETWEEN 482.8 TO 494 MHz (OSC/MULT BD’S 19D423266G3 & G7): A. IF THE RECEIVER HAS LESS THAN 8 ICOMS, REMOVE C407, C412, C417 .

REPLACE C407 WITH C2318 (10pF, N80). REPLACE C412 WITH C2319 (4pF, NPO).

B. IF THE RECEIVER HAS MORE THAN 8 ICOMS, REMO VE C407 , C41 2, C417 .

REPLACE C407 WITH C2320 (6pF, N80). REPLACE C412 WITH C2319 (4pF, NPO).

3. FOR RECEIVERS OPER ATING BETWEEN 500.8 TO 512.0 MHz (OSC/MULT BD’S 19D423266G4 & G8): A. IF THE RECEIVER HAS LESS THAN 8 ICOMS, REMOVE C407, C412, C417 .

REPLACE C407 WITH C2317 (8pF, N80). REPLACE C412 WITH C2321 (3pF, NPO).

B. IF THE RECEIVER HAS MORE THAN 8 ICOMS, REMO VE C407 , C41 2, C417 .

REPLACE C407 WITH C2316 (5pF, N80). REPLACE C412 WITH C2321 (3pF , NP0).

4. SOLDER ALL ELECTRICAL CONNECTIONS. DISCARD CAPACITORS NOT USED.

5. IN APPLICATION OF THIS KIT THE CRYSTAL OSCILLATOR FREQUENCY MUST BE CHANGED PER THE FOLLOWING FORMULA:

FX= Fo + 11.2

6. MARK ALL OSC/MUL T BD’S (19D42 3266) WITH A BLUE COLOR DOT IN T HE AREA OF THE PL DRAWING NO. PER 19A115740P1.

7. APPLY LABEL (19A130206P3) TO SIDE OF PLASTIC FRAME.

8. TEST AND ALIGN PER NORMAL PROCEDURE.

Figure 4 - Receiver Module Location Diagram

HIGH SIDE INJECTION

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