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GE MLSH041 Maintenance Manual Download Page 16

ALIGNMENT AND TROUBLESHOOTING PROCEDURES

16

LBI-38438A

5.2

TRANSMITTER

Alignment and troubleshooting for Transmitter circuitry on the Transmitter/Receiver
board CMN-233A/B.

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.

5.2.2

Measuring Instruments

1.

AVR (DC Power Supply DC 0-20V, 20A)

2.

Power Meter (usable at the value above 80 W)

3.

Directional Coupler

4.

Signal Generator

5.

Spectrum Analyzer

6.

Attenuator (30 dB, above 80 W)

7.

Tester

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Summary of Contents for MLSH041

Page 1: ...LBI 38438A Maintenance Manual Service Section MLS High Band Two Way Mobile Radios MLSH041 ...

Page 2: ... the United States This manual is published by Com Net Ericsson Critical Radio Systems Inc without any warranty Improvements and changes to this manual necessitated by typographical errors inaccuracies of current information or improvements to programs and or equipment may be made by Com Net Ericsson Critical Radio Systems Inc at any time and without notice Such changes will be incorporated into n...

Page 3: ...ZER BOARD 8 4 2 TO REMOVE THE TRANSMITTER RECEIVER BOARD 8 4 3 TO REMOVE THE FRONT PANEL CONTROL UNIT 8 5 ALIGNMENT AND TROUBLESHOOTING PROCEDURES 11 5 1 SYNTHESIZER 11 5 1 1 Test Equipment Required 11 5 1 2 TX VCO RX VCO Alignment 12 5 1 3 Transmitter Frequency Adjustment 13 5 1 4 Receiver Frequency Adjustment 13 5 1 5 Modulation Level Adjustment 13 5 1 6 Audio Check 14 5 1 7 Audio Output Level A...

Page 4: ...TMENT The transmitter has been adjusted at the factory and should require no readjustment However the antenna length should be adjusted for optimum VSWR and the frequency and modulation measured and recorded for future reference For the complete transmitter adjustment refer to the Alignment Procedure see Table of Contents 2 2 RECEIVER ADJUSTMENT No initial adjustments to the receiver are required ...

Page 5: ...es of water per cell per week is acceptable for batteries in continuous operation A weak battery will often cause excessive noise or faulty operation 3 1 3 Mechanical Inspection Since mobile units are subject to constant shock and vibration check for loose plugs nuts screws and parts to make sure that nothing is working loose 3 1 4 Antenna The antenna antenna base and all contacts should be kept c...

Page 6: ...stor to be positioned properly and the capacitors to fit into proper locations Refer to Figure 1 and trim the new transistor leads if required to the lead length of the removed transistor 5 Apply silicon grease to back of the replacement transistor and place the transistor into the mounting slot 6 Replace the transistor mounting screws using a moderate torque of 5 inch pounds 7 Tack solder the fou...

Page 7: ...e tinned end of the component on the tinned pad on the board and simultaneously touch the component and the pad with a well tinned soldering iron while pressing the component down on the board 3 Place the tinned soldering iron on the other end of the component and the pad simultaneously Apply solder to the top of the end of the component until the solder starts to flow Use as little solder as poss...

Page 8: ...F connecting the power supply cable to the board and turn the cable stopper mounted on the rear of the frame assembly 90 degrees Lift the cable stopper up and remove the power supply cable 4 Remove the two 2 screws I securing power module HC1 Remove the I screws securing the power transistors audio IC and AVR IC 5 Remove the two 2 screws J securing the board Carefully lift up and remove the board ...

Page 9: ...DISASSEMBLY PROCEDURES LBI 38438A 9 Figure 2 Disassembly Procedure Top View Figure 3 Disassembly Procedure Bottom View ...

Page 10: ...DISASSEMBLY PROCEDURE 10 LBI 38438A Figure 4 Disassembly Procedure Front Panel ...

Page 11: ... or circuit Troubleshooting procedures are provided for most major problems that might arise in the Transmitter the Receiver and the System Control Synthesizer Board 5 1 SYNTHESIZER Alignment and Troubleshooting for Synthesizer Circuitry on System Control Synthesizer Board CMC 551A B are detailed in the following subsections 5 1 1 Test Equipment Required 1 Audio Oscillator 2 Deviation Monitor 3 Os...

Page 12: ... 0 MHz Select highest frequency transmit channel With 50 ohm load on the antenna connector J1 key the radio Monitor TP201 with a digital voltmeter and tune L206 for 7 0 VDC 0 1 V Unkey the radio 2 TP201 CV201 7 0 VDC Select the highest frequency receive channel Monitor TP201 with digital voltmeter and tune CV201 for 7 0 VDC 0 1 V 3 TP201 3 5 7 5 VDC Select lowest frequency channel Voltage should b...

Page 13: ...1 3 Transmitter Frequency Adjustment STEP METERING POINT TUNING CONTROL METER READING 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 1 J201 or J1 FREQ TRIM Control on TCXO XU201 Channel Operating Freque...

Page 14: ...level and set LOOP MOD ADJUST RV203 for a deviation of 2 kHz Unkey the radio 6 Disconnect the audio oscillator and replace P602 in position 1 2 7 Select a frequency with Tone Channel Guard 8 Key the radio and set CG DEVIATION ADJUST RV202 for a deviation reading of 0 75 kHz NOTE If Channel Guard is not used on any frequency channel CG DEV ADJUST RV201 may be set for 4 5 kHz deviation instead of 3 ...

Page 15: ...on 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 Terminate J701 1 6 with a 4 ohm 6 watt resistor connect the audio level meter and the distortion analyzer input across the resistor Set the volume to the maximum point Press DOWN button two times Adjust RV601 for 4 watt output 4 Vrms using the distor...

Page 16: ...33A B 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 2 Measuring Instruments 1 AVR DC Power Supply DC 0 20V 20A 2 Power Meter usable at the value above 80 W 3 Directional Coupler 4 Signal Generator 5 Spectrum Analyzer 6 Attenuator 30 dB above 80 W 7 Tester ...

Page 17: ...firm voltage of TR8 collector is 9V at TP4 and that the relay K1 clicks at this time 3 Setting APC off power RV1 RV2 Connect RF cable P101 to J201 Turn the control RV1 on APC fully clockwise CW Next turn the volume RV2 slowly CW and set an output of 70W 2W at the highest frequency of each band 4 Confirming minimum power RV1 Turn the volume RV1 on APC fully CCW and confirm minimum power of 30W or l...

Page 18: ...ALIGNMENT AND TROUBLESHOOTING PROCEDURES 18 LBI 38438A 5 2 5 Transmitter Troubleshooting ...

Page 19: ...ALIGNMENT AND TROUBLESHOOTING PROCEDURES LBI 38438A 19 ...

Page 20: ...Hz 2 DC Voltmeter 3 Frequency Counter up to 100 MHz with 0 05 V sensitivity 4 Audio Level Meter and Distortion Analyzer 5 4 ohm 6 Watt Resistor 5 3 1 2 Preliminary Adjustment 1 Connect 13 8 VDC to P2 2 Set MONITOR switch to out position 3 Select desired channel 4 Disable Channel Guard by connecting ground to J701 7 5 Connect RF Signal Generator to antenna jack J1 NOTE Make sure the transmitter is ...

Page 21: ... J701 1 6 with a 4 ohm 6 watt resistor Connect the Audio Level Meter and Distortion Analyzer input across the resistor Adjust the volume control for 4 W output 4 0 Vrms using Audio Level Meter 4 J701 1 6 L503 L505 L510 See Procedure Set the output signal level of RF signal generator so as to obtain 12 dB SINAD at audio output Adjust coils L503 L505 and L510 to obtain maximum 12 dB SINAD sensitivit...

Page 22: ...or 5 3 5 Test Procedure 5 3 5 1 STEP 1 AUDIO OUTPUT AND DISTORTION Measure Audio Power Output as follows 1 Apply a 1000 microvolt on frequency test signal modulated by 1000 Hz with 3 0 kHz deviation to antenna jack J1 2 With 4 Watt Speaker Disconnect speaker plug if present Connect a 4 0 ohm 6 watt load resistor across the external speaker loads 3 Adjust the VOLUME control for rated power output o...

Page 23: ...ve all controls as they are and all equipment connected if the Modulation Acceptance Bandwidth test is to be performed SERVICE CHECK If the sensitivity level is more than rated 12 dB SINAD check the alignment of the IF stage as directed in the Alignment Procedure 5 3 5 3 STEP 3 MODULATION ACCEPTANCE BANDWIDTH OR IF BANDWIDTH If Steps 1 and 2 check out properly measure the bandwidth as follows 1 Se...

Page 24: ...ALIGNMENT AND TROUBLESHOOTING PROCEDURES 24 LBI 38438A 5 3 5 4 Receiver Troubleshooting ...

Page 25: ...ALIGNMENT AND TROUBLESHOOTING PROCEDURES LBI 38438A 25 ...

Page 26: ...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 A ...

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