LBI-38425A Maintenance Manual Service Section MLS II Highband Two-Way Mobile Radios MLSH041
LBI-38425A GENERAL INFORMATION NOTICE! Repairs to this equipment should be made only by an authorized service technician or facility designated by the supplier. Any repairs, alterations or substitution of recommended parts made by the user to this equipment not approved by the manufacturer could void the user's authority to operate the equipment in addition to the manufacturer's warranty. NOTICE! The software contained in this device is copyrighted by Com-Net Ericsson Critical Radio Systems, Inc.
TABLE OF CONTENTS LBI-38425A TABLE OF CONTENTS Page 1 Description................................................................................................................................................ 4 2 Initial Adjustment .................................................................................................................................... 4 2.1 Transmitter Adjustment ...............................................................................................................
LBI-38425A 1 DESCRIPTION AND INITIAL ADJUSTMENT DESCRIPTION The service section contains the information necessary for aligning and troubleshooting the MLS II (MLSH041) two-way FM mobile radio. In addition, information is provided for removing and replacing chip components, disassembly procedures and module replacement procedures.
MAINTENANCE 3 LBI-38425A MAINTENANCE 3.1 PREVENTIVE MAINTENANCE To insure high operating efficiency and to prevent mechanical and electrical failures from interrupting system operations, routine checks should be made of all mechanical and electrical parts at regular intervals. Preventive maintenance should include the following checks: 3.1.
LBI-38425A MAINTENANCE 3.1.7 Disassembly To gain access to the transmitter, receiver, and the system control/synthesizer for servicing, loosen the four screws securing the cover at the rear of the radio. Then pull the cover out from under the edge of the front panel and lift the cover off. 3.2 DRIVER REPLACEMENT 3.2.1 To Remove Driver HC1 1. Remove the two screws securing HC1 to the printed wire board. 2.
MAINTENANCE LBI-38425A 1. Remove the two retaining screws securing PA transistor TR1 to chassis assembly. 2. Unsolder and remove capacitors. Use a desoldering tool as necessary while lifting the transistor leads with a small screwdriver or pick. Discard old capacitors. 3. Unsolder the emitter, base, and collector leads of the transistor, and remove it from the printed board. 4.
LBI-38425A 3.4 MAINTENANCE CHIP COMPONENT REPLACEMENT Replacement of chip capacitors should always be done with a temperature controlled soldering iron, using a controlled temperature of 700°F (371°C). However, DO NOT touch black metal film of the resistors or the ceramic body of capacitors with the soldering iron. The metallized end terminations of the parts may be touched with the soldering iron without causing damage. NOTE 3.4.1 To Remove Chip Components 1.
DISASSEMBLY PROCEDURE 4 LBI-38425A DISASSEMBLY PROCEDURE 4.1 TO REMOVE THE SYSTEM CONTROL/SYNTHESIZER BOARD 1. Remove the two (2) screws ! securing the top cover (refer to Figure 3). Remove the top cover. Then disconnect the interconnecting cables. 2. Remove the eight (8) screws " securing the Synthesizer shield. Remove the shield. 3. Remove the three (3) screws # securing the board. 4. Remove the screws $ securing regulator and carefully lift up and remove the board.
LBI-38425A 4.2 DISASSEMBLY PROCEDURE TO REMOVE THE TRANSMITTER/RECEIVER BOARD 1. Remove the screws ! and % securing the top cover and the bottom cover (refer to Figures 3 & 4). 2. Disconnect the interconnecting cables and then remove the seven (7) screws & securing the shield to the board. 3. Disconnect the interconnecting cable. Remove the four (4) screws ' securing the antenna shield. 4.
DISASSEMBLY PROCEDURE LBI-38425A Figure 4 – Disassembly Procedure (Bottom View) Figure 5 – Disassembly Procedure (Front Panel) 11
LBI-38425A 5 ALIGNMENT AND TROUBLESHOOTING PROCEDURES ALIGNMENT AND TROUBLESHOOTING PROCEDURES Radio maintenance is facilitated by using the Troubleshooting Procedures and servicing techniques unique to this radio. The Troubleshooting Procedures are designed to lead the serviceman rapidly to the defective component or circuit. Troubleshooting procedures are provided for most major problems that might arise in the System Control/Synthesizer Board, the Transmitter, and the Receiver. 5.
ALIGNMENT AND TROUBLESHOOTING PROCEDURES LBI-38425A 5.1.2 TX VCO & RX VCO Alignment STEP 1 METERING POINT TP201 Control Voltage Monitor TUNING CONTROL CV202 METER READING 4.0 VDC 7.0 VDC 2 TP201 CV201 7.0 VDC 3 TP201 3.5-7.5 VDC 4 J201 +2 to +8 dBm PROCEDURE In case that highest transmit frequency is < 156.8 MHz. Select lowest frequency transmit channel. With 50 ohm load on the antenna connector J1, key the radio. Monitor TP201 with digital voltmeter and tune CV202 for 4.0 VDC ±0.1 V.
LBI-38425A ALIGNMENT AND TROUBLESHOOTING PROCEDURES 5.1.3 Transmitter Frequency Adjustment STEP METERING POINT TUNING CONTROL METER READING 1 J201 (or J1) FREQ TRIM Control on TCXO (XU201) Channel Operating Frequency PROCEDURE NOTE This step assumes the frequency is measured when the transmitter is first keyed. If delayed, the rapidly rising ambient temperature must be taken into consideration. The Oscillator frequency should be set at 25°C ambient temperature.
ALIGNMENT AND TROUBLESHOOTING PROCEDURES LBI-38425A 5.1.4 Receiver Frequency Adjustment 1. No receiver frequency adjustment is required. 2. With proper alignment of EX injection frequency, RX injection frequency will automatically be correct. 5.1.5 Modulation Level Adjustment Procedure for synthesizer Transmit Deviation 1. Select the highest frequency channel. 2. Rotate CG DEV ADJUST, RV202 fully counterclockwise. 3. Connect the audio oscillator and apply a 1 kHz tone at 850 mVrms to MIC HI, J7014.
LBI-38425A ALIGNMENT AND TROUBLESHOOTING PROCEDURES 5.1.7 Audio Output Level Adjustment Procedure STEP METERING POINT TUNING CONTROL METER READING 1 J701-1 RV601 See Procedure PROCEDURE Set the signal generator to the receiver frequency with ±3 kHz deviation and 1 kHz modulation. Set the RF signal level to 1000 microvolts. Move P551 from J551-1, 2 to J551-2, 3 on the Transmitter/Receiver Board. Connect RF signal generator to J1.
ALIGNMENT AND TROUBLESHOOTING PROCEDURES LBI-38425A 5.1.
LBI-38425A 5.2 ALIGNMENT AND TROUBLESHOOTING PROCEDURES TRANSMITTER Alignment and troubleshooting procedures for Transmitter circuitry on the Transmitter/Receiver board CMN-233 are as follows: 5.2.1 General Description of Adjustment This manual is prepared for adjustments and confirmations of the Exciter/PA section and covers the following items: 5.2.
ALIGNMENT AND TROUBLESHOOTING PROCEDURES LBI-38425A ADJUSTMENT SYSTEM * 30 dB ATT SPECTRUM ANALYZER AVR POWER SUPPLY DIRECTIONAL COUPLER POWER METER RADIO SPECTRUM ANALYZER * FOR MEASURING SPURIOUS ONLY.
LBI-38425A ALIGNMENT AND TROUBLESHOOTING PROCEDURES 5.2.3 Transmitter Adjustment Procedure TEST POINT TUNING CONTROL STEP ITEM PROCEDURE 1 Initial Setting Turn the volume on APC RV1, RV2 fully counterclockwise (CCW). 2 Confirming the voltage Disconnect RF cable P101 from connector J201. Turn on the power. Turn on the PTT (ground J7012). Confirm voltage of TR6 collector is 9V at TP4 and that the relay K1 clicks at this time. TP4 3 20 Setting APC off power Connect RF cable P101 to J201.
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ALIGNMENT AND TROUBLESHOOTING PROCEDURES 5.3 LBI-38425A RECEIVER Alignment and Troubleshooting procedures for Transmitter/Receiver Board CMN-233 are as follows: Receiver Circuitry on 5.3.1 Receiver Alignment Equipment Required: • RF Signal Generator (150.8 – 174 MHz) • DC Voltmeter • Frequency Counter (up to 500 MHz with 0.05 V sensitivity) • Audio Level Meter and Distortion Analyzer • 4 Ohm, 6 Watt Resistor 5.3.1.1 1. Preliminary Adjustment Connect 13.8 VDC to P2. 2.
LBI-38425A ALIGNMENT AND TROUBLESHOOTING PROCEDURES 5.3.2 Alignment Procedure STEP TEST POINT TUNING CONTROL METER READING PROCEDURE 9.0 ± 0.2 VDC Connect the DC Voltmeter to TP501. 1 TP501 2 TP504 L511 See Procedure Connect RF signal probe from the frequency counter to TP504. Check for a reading of 81.745 MHz ±200 Hz. 3 TP503 L513 See Procedure Set the signal generator on the receive frequency with ±3 kHz deviation and 1 kHz modulation. Set the RF signal level to 1000 microvolts.
ALIGNMENT AND TROUBLESHOOTING PROCEDURES LBI-38425A 5.3.3 Fixed Squelch Adjustment 1. Disable Channel Guard, if present, (ground J701-7). Set Squelch control RV502 full CCW. 2. Connect a signal generator to antenna jack J1 and adjust for nominal 8 dB SINAD signal. 3. Adjust squelch control RV531 to maximum squelch. Receiver must be muted. 4. Adjust squelch control RV531 slowly until receiver unmutes. 5. Check that the squelch opens at an input signal level corresponding to 8 dB SINAD (±1 dB). 6.
LBI-38425A ALIGNMENT AND TROUBLESHOOTING PROCEDURES 3. Adjust the VOLUME control for rated power output of 4 watts (4.0 Vrms across the 4 ohm load) using the Distortion Analyzer as a voltmeter. 4. Make distortion measurements according to manufacturer’s instructions. Reading should be less than 5%. If the receiver sensitivity is to be measured, leave all controls and equipment as they are.
ALIGNMENT AND TROUBLESHOOTING PROCEDURES LBI-38425A 1. Set the Signal Generator output for twice the microvolt reading obtained in the 12 dB SINAD measurement. 2. Set the Range control on the Distortion Analyzer in the SET LEVEL position (1000 Hz filter out of the circuit), and adjust the input LEVEL control for a +2 dB reading on the 30% range. 3.
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Com-Net Ericsson Critical Radio Systems, Inc. P.O. Box 2000 Lynchburg, Virginia 24501 Phone: 1-800-431-2345 or (Outside USA, 1-804-592-6100) www.com-netericsson.com Printed in U.S.A.
