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LBI-31511B
MAINTENANCE MANUAL
403-430 MHz & 450-512 MHz, DELTA-S NARROWBAND
TWO WAY FM RADIO
SERVICE SECTION
TABLE OF CONTENTS
Page
DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Front Cover
INITIAL ADJUSTMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Front Cover
MAINTENANCE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
PREVENTIVE MAINTENANCE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
DISASSEMBLY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
PA TRANSISTOR REPLACEMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
REMOVING IC’s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
REPLACING CHIP COMPONENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1
2
1
1
2
2
PROGRAMMING AND ALIGNMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
SERVICE TIPS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
TEST AND TROUBLESHOOTING PROCEDURES . . . . . . . . . . . . . . . . . . . . . . .
TRANSMITTER ALIGNMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
RECEIVER ALIGNMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
RECEIVER AUDIO AND SQUELCH WAVEFORM CHECKS . . . . . . . . . . . . . . . . . .
MECHANICAL LAYOUT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
INTERCONNECTION DIAGRAMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2
3
4
7
11
14
15
17
DESCRIPTION
•
•
Alignment procedures for the transmitter and receiver.
Troubleshooting flow charts and waveforms.
The service section of this manual contains the diagnostic routines, and other maintenance information to service this radio. The service section includes:
•
•
•
System interconnections.
•
Mechanical layout.
Disassembly procedures.
Replacement of IC’s chip capacitors and resistors.
INITIAL ADJUSTMENT
After the radio has been installed (as described in the
Installation Manual), the following adjustments should be made by a certified electronics technician.
Printed in U.S.A.
LBI-31511
TRANSMITTER ADJUSTMENT MAINTENANCE
The adjustment for the transmitter includes measuring the forward and reflected power and adjusting the antenna length for optimum ratio, then setting the transmitter to rated power output.
Next, measure the frequency and modulation and record these measurements for future reference. For the complete transmitter adjustment, refer to the Alignment Procedure (see Table of
Contents).
PREVENTIVE MAINTENANCE
To ensure 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. This preventive maintenance should include the checks as listed in the table of Maintenance Checks.
MAINTENANCE CHECKS
CONNECTIONS - Ground connections and connections to the voltage source should be periodically checked for tightness. Loose or poor connections to the power source will cause excessive voltage drops and faulty operation. When ground connections are not made directly to the battery, the connection from the battery to vehicle chassis must be checked for low impedance. A high impedance may cause excessive voltage drips and alternator noise problems.
INTERVAL
6 Months
As
Required
X
ELECTRICAL SYSTEM - Check the voltage regulator and alternator or generator periodically to keep the electrical system within safe and economical operating limits. Overvoltage is indicated when the battery loses water rapidly. Usage of 1 or 2 ounces of water per cell per week is acceptable for batteries in continuous operation. A weak battery will often cause excessive noise or faulty operation.
X
X 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. Be sure that all screws are properly torqued.
ANTENNA - The antenna, antenna base and all contacts should be kept clean and free from dirt or corrosion. If the antennas or its base should become coated or poorly grounded, loss of radiation and a weak signal will result.
ALIGNMENT - The transmitter and receiver meter readings should be checked periodically, and the alignment "touched up" when necessary. Refer to applicable Alignment Procedure and troubleshooting sheet for typical voltage readings.
FREQUENCY CHECK - Check transmitter frequency and deviation. Normally, these checks are made when the unit is first put into operation, after the first six months and once a year thereafter.
X
X
X
DISASSEMBLY
•
To gain access to the unit for servicing:
1.
Unlock the radio.
2.
Pull down the handle.
3.
Pull the radio forward and lift radio out of mounting place -- if desired.
4.
Pry up the front of top cover and lift the cover off.
5.
To gain access to the bottom side, pull the radio all the way out of the mounting frame and remove the four mushroom shaped feet using a #30 Torx® screwdriver.
NOTE
With the top cover removed all components on the
PA and TRS board are accessible for tuning. The PA,
IF, and synthesizer/exciter covers must be removed to expose components.
•
To remove the TRS board:
1.
Remove the bottom cover.
2.
Remove the eleven retaining screws at (A) (Figure 1) securing the circuit board to the main frame.
3.
Remove two retaining screws (B) securing systems connector J601 to front casting.
4.
Unsolder the two feed through capacitor terminals
(E) on printed wire pattern.
5.
Turn over the radio and remove the three retaining screws (D) (Figure 2) securing the audio bridge amplifier, U601 and U602, and the 5 and 9 volt regulators U702 and Q705 to the side of chassis.
6.
To remove the front end shield, remove the 20 retaining screws securing the shield to the front end casting and remove.
7.
To remove the synthesizer shield, remove the seventeen retaining screws securing the shield to the synthesizer top casting.
Copyright© September 1985, General Electric Company
Figure 1 - Disassembly - Bottom View
Figure 2 - Disassembly - Top View
LBI-31511
1
LBI-31511
•
To replace TRS board:
1.
Perform above procedures in reverse order.
•
To remove the PA board:
1.
Remove the three retaining screws (G) securing the
PA filter cover to the main frame.
2.
Remove the eight retaining screws (F) from around the edge of the PA board.
3.
Remove the two retaining screws (H) securing the antenna connector to the main frame.
4.
Loosen the retaining screw (J) securing the pass transistor to the side of the PA chassis compartment.
5.
Remove the retaining screws (K) securing the PA transistors to the main frame.
6.
Turn the radio over and remove the nut and washer from the stud of PA transistor Q1.
NOTE
Torque #8 nut on Q1 to 6 inch pounds when replacing.
7.
Unsolder the two power feed through capacitors at
(L).
8.
Carefully lift the PA board up off the pins extending upward from the TRS board.
NOTE
Note the position of the copper washer spacer under transistor Q1. Be sure that this spacer is in place when replacing the board.
PA TRANSISTOR REPLACEMENT
WARNING
The RF Power Transistors used in the transmitter contain Beryllium Oxide, a TOXIC substance. If the ceramic or other encapsulation is opened, crushed, broken or abraded, the dust may be hazardous if inhaled. Use care in replacing transistors of this type.
•
To replace the PA RF transistors:
1.
Unsolder one lead at a time with a 50 watt soldering iron. Use a scribe or X-acto® knife to hold the lead away from the printed circuit board until the solder cools.
2.
Remove retaining screws and lift out the transistor.
Remove any old solder from the printed circuit board with a vacuum desoldering tool. Special care should be taken to prevent damage to the printed circuit board runs because part of the matching network is included in the base and collector runs.
3.
Trim the new transistor leads (if required) to the lead length of the removed transistor. The letter "C" on the top of the transistor also indicates the collector.
4.
Apply a coat of silicon grease to the transistor mounting surface. Place the transistor in the mounting hole.
Align the leads as shown on the Outline Diagram.
Then replace the transistor mounting screws using moderate torque.
5.
Solder the leads to the printed circuit pattern. Start at the inner edge of mounting hole and solder the remaining length of transistor lead to the board. Use care not to use excessive heat that causes the printed wire board runs to lift up from the board. Check for shorts and solder bridges before applying power.
•
To replace the PA board:
1.
Perform the above procedures in reverse order, being careful to realign all interconnecting pins and sleeves. Be sure the antenna gasket between the antenna jack and front casting is positioned properly.
CAUTION
Failure to solder the transistor leads as directed may result in the generation of RF loops that could damage the transistor r may cause low power output.
LBI-31511
REMOVING IC’s
3.
Remove excess solder with a vacuum solder extractor.
4.
Carefully remove the epoxy adhesive and excess flux to prevent damage to the printed board.
Removing IC’s (and most other soldered-in components) can be easily accomplished by using a vacuum desoldering tool.
To remove an IC, heat each lead separately on the solder side and remove the old solder with the desoldering tool.
CAUTION
The CMOS Integrated Circuit devices used in this equipment can be destroyed by static discharges. Before handling one of these devices, the serviceman should discharge himself by touching the case of a bench test instrument that has a 3-prong power cord connected to an outlet with a known good earth ground. When soldering or desoldering a CMOS device, the soldering iron should also have a 3-prong power cord connected to an outlet with a known good earth ground. A batteryoperated soldering iron may be used in place of the regular soldering iron.
To Replace Chip Components
1.
Using as little solder as possible, "tin" one end of the component and one of the pads on the printed wiring board.
2.
Place the "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 possible while getting a good joint.
4.
After the component has cooled, remove all flux from the component and printed wiring board area with alcohol.
PROGRAMMING AND ALIGNMENT
REPLACING CHIP COMPONENTS
Replacement of chip components 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 following procedure describes how to change the frequencies in the radio EEPROM(S) for new user frequencies.
Also included is an alignment procedure guide to assist you in aligning the radio after the frequencies have been changed. The alignment procedure should be performed in the order given and it must be performed prior to putting the radio back in service.
PROGRAMMING
NOTE
The metallized end terminations of the parts may be touched with the soldering iron without causing damage.
To Remove Chip Components
1.
Grip the component with tweezers or needle nose pliers.
2.
Alternately heat each end of the chip in rapid succession until solder flows, and then remove and discard the chip.
The DELTA-S UHF Narrowband radio may be programmed using the TQ-2310 Suitcase Programmer, the 4EX22A10 Hand
Programmer or by a Personal Computer. The procedures for using the programmers are covered in detail in LBI-31263 (TQ-
2310) and LBI-31275 (4EX22A10). TQ-3334 provides the software and programming instructions for programming with a PC.
When programming the radio, consideration must be given to the individual band split for the T/R/S board. See the Programming tips on the following page and the individual band splits listed below.
2
LBI-31511
BAND
SPLIT
450-470 MHz
470-494 MHz
494-512 MHz
403-430 MHz
450-470 MHz
470-494 MHz
494-512 MHz
403-430 MHz
T/R/S BOARD
(NEG. GRD. ONLY)
19D901620G1 (Tin Cont.)
19D901620G2 (Tin Cont.)
19D901620G3 (Tin Cont.)
19D901620G4 (Tin Cont.)
19D901620G5 (Gold Cont.)
19D901620G6 (Gold Cont.)
19D901620G7 (Gold Cont.)
19D901620G8 (Gold Cont.)
T/R/S BOARD
(FLOATING GRD.)
19D900920G1
19D900920G2
19D900920G3
19D900920G4
MICROCOMPUTER SOFTWARE (U705)
The latest software package is a 19A703244P23 or a
19A703868G5; replacing the following packages:
Narrowband
19A703244P10
19A703241G3-8
PROGRAMMING TIPS
Wideband
19A703244P21,22
19A703868G2-4
When programming with the Suitcase Programmer or a
Personal Computer, Jumper P707 (if present on Negative
Ground System Boards only) must be removed. If programming the S950/S990 Control Unit for download to the radio, P703 on the rear of Control Unit must be disconnected to isolate Advance
Change Pulse Line.
When the 4EX22A10 Hand Programmer, Jumper P706
(Negative Ground T/R/S Boards) must be removed (to disconnect D720), or lift one end of D720 on Floating Grd T/R/S
Boards.
ALIGNMENT
4.
Tune the exciter.
5.
Adjust transmitter power amplifier.
6.
Set the reference oscillator frequency (one setting for both transmit and receive).
UNDER RECEIVE ALIGNMENT SECTION
1.
Adjust local oscillator-buffer injection.
2.
Adjust front end.
3.
Adjust IF selectivity.
4.
Adjust FM detector/audio pre-amp.
SERVICE TIPS
CHANNEL GUARD BOARD
When servicing the transmit/receive/synthesizer board it may be helpful to remove and relocate the Channel Guard board.
Both the Channel Guard board and Channel Guard extender may be removed and set aside during servicing. While servicing the radio install P608 to connect VOL/SQ/HI.
After the radio has been programmed with new user frequencies, the radio re-alignment procedure is as follows:
UNDER SYNTHESIZER AND TRANSMITTER
ALIGNMENT PROCEDURE
1.
Check 9 volt regulator.
2.
Adjust the synthesizer transmitter VCO.
3.
Adjust the synthesizer receiver VCO.
NOTE
Typical voltage readings are provided on the Schematic
Diagram for reference when troubleshooting.
LBI-31511
MICROCOMPUTER
When servicing the microcomputer/synthesizer circuitry it is sometimes desirable to force the microcomputer into specific operating modes. Following are some tips that allow you to initiate these modes.
•
To force the microcomputer to continually try to reload the synthesizer. This mode will enable you to check the serial data, clock, channel change pulse and enable signals to the synthesizer. Grounding the lock detect line into the microcomputer at U703-8.
•
To stop the microcomputer from running, disable the watchdog timer by shorting the collector and emitter of Q714 and ground the single step line at U705-5.
When servicing the radio be sure that no solder buildup has occurred on the chassis or shield.
To assure a high degree of resistance to microphonics be sure to replace exactly, all hardware removed. Be sure that all mounting screws are properly torqued and shields in place.
Refer to Mechanical Layout Diagram.
NOTE
Loose or rubbing parts, especially in the VCO area are particularly sensitive and can cause microphonics. Again be certain all hardware is properly installed and torqued.
MICROPHONICS
TEST FREQUENCIES
Synthesized radios tend to be sensitive to shock and vibration, creating microphonics. The construction of the
DELTA-S, radio with its die cast aluminum frame, cast shields, and multiple board mounting screws, provides a high degree of immunity. When removing either printed circuit board or the shields, note the exact location and position of all mounting hardware including rubber padding and bracket (if included).
If the EEPROM is not custom programmed to the customers specified personality, then a standard test program is provided. The EEPROM is programmed on channels 1 through
16 including tone and digital Channel Guard and carrier control timer. Table 1 identifies the programmed test frequencies.
3
LBI-31511
SIGNAL LEVELS
CAS
RUS
SIGNAL
Sq Dis, Input
CCT Sq Dis, Input
TX Enable
PTT, Input
CURRENT REFERENCE CHART
SERVICE
PLUG
P701
P702
P703
P704
P705
J353
J352
J712
TYPICAL PERFORMANCE INFORMATION
INDICATION
High Level
Low Level
High Level (RX Un-sq)
Low Level (RX Squelched)
Low Level (RX Mute/PTT)
Pulled low (RX unsquelched)
Logic Low (Sq. Dis)
Logic High (Sq)
RX Un-Sq
Logic Low
Logic High
Logic Low
Logic High
Logic Low
Logic High
VOLTAGE LEVEL
9.0 Vdc
0.15 Vdc
9.0 Vdc
0.15 Vdc
0.6 Vdc
0 Vdc
2.4 Vdc
0.14 Vdc
0.35 Vdc
5.5 Vdc
2.0 Vdc
9.0 Vdc
1.0 Vdc
13 Vdc
TROUBLESHOOTING PROCEDURE
(Cont.)
TYPICAL PERFORMANCE INFORMATION
RADIO CONNECTOR IDENTIFICATION
Front Connector
Systems Metering
Option Connector
PROM Program Plug
RF Metering
RX Input
IF Input
RX Inj.
Exciter Input
Exciter Output
Hand Programmer Enable
Program Disable
TX PA Metering
VG Interface
Fixed Squelch
Channel Guard
Aux Audio
DPTT
IGN A+
J601
J602
J603
J711
J101
P401
P404
P451
P102
P101, P103
P706
P707
J1
P612
P605
P608
P610
P402
P403
FUNCTION
5V
9V
9V
9V
9V
TYPICAL CURRENT/mA
75
70
TX 90, RX 80
TX 45, RX 75
TX 40, RX 55
EXCITER
LBI-31511
RECEIVER READINGS SYSTEM JACK, J602
TEST POS FUNCTION
D
H
IF AMP
RX INJ
SCALE
1V
1V
TYPICAL
READING
0.75
0.55
TRANSMITTER QUICK CHECKS
– Connect red system metering plug to J602, system metering.
– Connect black plug of GE Test Set to RF Metering jack J101. Set polarity to "+" and voltage range to the 1 volt position (Test 1).
TEST POINT DATA (Typical)
TEST POINT
J602-3
J602-2
J202
VOLTAGE
9.0
±
0.05 Vdc
13.2 Vdc (A+)
3.0-7.5 Vdc
0.7 VPP
5.5 Vdc (Nominal)
5.0 Vdc
CONTROL
R703
DESCRIPTION
9 Volt Regulator
C220 (RX)
L209 (TX)
VCO Control Voltage
(See Synth Align)
Reference Osc. Output (high impedance)
Reference Oscillator compensation line voltage
VCC to Microcomputer
RANGE
POSITION
TEST 1
TEST
POS.
A
TEST 1
TEST 1
B
C
METERING
JACK J101
J101-10
J101-9
J101-8
RF METERING J101
EXCITER READINGS
PROBABLE CAUSE
METERING READINGS
FUNCTION
METER
SCALE
TYPICAL
READING
AMPL-1 0-1 0.2V
TRIPLER
AMPL-3
REL PWR
OUT
0-3
0-1
0.2V
0.5V
HIGH
Q101
Shorted
R 1 0 1 , R 1 0 3
Open
Q102
Defective; R107
Open
H e l i c a l C o i l
L114
Shorted Or
Mis-tuned
LOW
Q101 Open; R103, R105,
O p e n ; L 1 0 3 O p e n ;
O s c i l l a t o r / B u f f e r
Defective
Q102 Shorted; R110 Open;
L104, L105, and associated c i r c u i t s , d e f e c t i v e o r improperly tuned.
Q103 OR Q104 defective.
Check resistors, capacitors around Q103 and Q104.
Helical coils L107, L108 m is - t un ed o r de f ec ti v e.
D 1 0 1 a n d a s s o c i a t e d metering circuits defective.
(Cont.)
4
LBI-31511 TROUBLESHOOTING PROCEDURE
PA QUICK CHECKS
– Connect red system metering plug to J602, system metering.
– Connect black plug of GE Test Set of RF Metering jack J1 of PA. Set polarity to "+" and voltage range to the 1 volt position (Test 1).
LBI-31511
(Cont.)
PA TROUBLESHOOTING PROCEDURE
When troubleshooting the transmitter check for typical meter readings for the exciter, J101, and the power amplifier JACK,
J1. Typical readings for the various test positions and test points are given in the charts below.
NOTE
Regulated +5 Vdc and +9 Vdc can be opened by P701 thru P705 to facilitate troubleshooting.
POWER AMPL METERING J1
PA JACK READINGS
80, 90
100W
35, 40
50W
65,
75W
TEST
POS.
METERING
POINT
FUNCTION
MEASURED
SCALE
TYPICAL
READING
TYPICAL
READING
TYPICAL
READING
METER
READING
PROBABLE CAUSE
HIGH LOW
A
B
C
J1-10 RF DRIVE
J1-9 CONTROL
VOLTAGE
0-1 V
0-15V
0.5 V
4 V
J1-8 TX 0-15V 12.5V
0.5 V
4.5 V
12.5V
0.5V
7.5V
12.5V
L o w e x c i t e r output
L o w e x c i t e r o u t p u t .
Realign or repair exciter.
High exciter output.
E
F
J1-6 PA
CURRENT
J1-5 DRIVER
CURRENT
0-15A
15 A
5 A
---
8 A
11A
4A
Excessive voltage drop in power cable.
RF output low.
R F o u t p u t e x c e s s i v e l y high. Be sure a n t e n n a i s p r o p e r l y matched to 50 ohms.
1 0 0 W A T T
PA C h e c k
A 1 Q 5 a n d
A 1 Q 6 . B e s ur e a ntenna i s p r o p e r l y matched to 50 ohms.
40 WATT PA
R F o u t p u t p o w e r i s excessive. Be s ur e a ntenna i s p r o p e r l y matched to 50 ohms.
100 WATT PA A1Q5 a n d A 1 Q 6 h a v e excessive gain. RF gain.
RF output set too low.
40 WATT PA Low RF output.
SYMPTOM PROCEDURE
Little or No
RF Output
Key transmitter and check J1-10 (Pos A) for +0.5
V (exciter output).
Unkey transmitter and check Q105-C for +9.0
Vdc.
Check DC voltages on Q101-Q105.
readings.
ANALYSIS
Refer to Schematic Diagram and verify voltage
Verify +9.0 volt supply. Check R124 and L117.
Disconnect P102 on Exciter and measure RF output of synthesizer.
If voltages are incorrect, check L103, L106, L110,
L112, L117 and all resistors for each stage. Check
R106, R110, R114, R118, R119 and R124. Check
Q101-Q105. Replace components if defective.
No RF present: see Synthesizer Troubleshooting
Procedure.
RF present: reconnect P102 and proceed to next step.
Key transmitter and monitor voltage at J101-9
(Pos B Tripler). Voltage should increase.
Monitor J101-8 (Pos C) and key transmitter.
Voltage should increase.
Disconnect P103 on exciter and measure RF output power from exciter. Should be 0.5 watts or more.
If voltage does not increase check Q116-Q118, L106 and associated components.
If voltage does not increase, check Q103, Q104 and associated components. Check D101 and associated metering circuitry. Finally, check both helical filters.
If exciter output is low, check Q105 and associated circuitry. Also check 2nd helical filter including L114 and L115. Retune exciter if needed.
If output power is correct be sure P101 is soldered securely and that it mates properly with the contact on the power amplifier.
(Cont.)
5
LBI-31511
TEST PROCEDURE
These Test Procedures are designed to help you to service a receiver that is operating -- but not properly. The problems encountered could be low power, poor sensitivity, distortion, limiter not operating properly and low gain. By following the sequence of test steps starting with Step 1, the defect can be quickly localized. Once the defective stage is pin-pointed, refer to the "Service Check" listed to correct the problem.
Additional corrective measures are included in the Troubleshooting Procedure. Before starting with the Receiver Test
Procedures, be sure the receiver is tuned and aligned to the proper operating frequency.
TEST EQUIPMENT REQUIRED
•
•
Distortion Analyzer
Signal Generator
•
6 dB attenuation pad
•
Audio Isolation Transformer
•
4 ohm resistor (15 watt minimum)
PRELIMINARY ADJUSTMENTS
NOTE
These procedures are written around the Heathkit
Distortion Analyzer. If a Distortion Analyzer other than the Heath IM-12 is used, measure the sensitivity and modulation acceptance bandwidth in accordance with manufacturer’s instructions.
1.
Unsquelch the receiver.
RECEIVER TEST PROCEDURE
STEP 1
AUDIO POWER OUTPUT
AND DISTORTION
TEST PROCEDURE
Measure Audio Power Output as follows:
A. Apply a 1000 microvolt, on-frequency test signal modulated by 1,000 Hz with
±
3.0 kHz deviation to antenna jack J2.
B. With 12 Watt Speaker
Disconnect speaker lead pins from J1A-36 and 37 on rear of control unit. Connect a 4.0 ohm, 15 watt load resistor across system metering jack J602-6 and 7 on the TRS board.
Connect the isolation transformer input across the resistor. Connect the isolation transformer output to the Distortion Analyzer (See Figure 5).
C. Adjust the VOLUME control for 12 watts output
6.93 VRMS using the Distortion Analyzer as a voltmeter.
D. Make distortion measurements according to manufacturer’s instructions. Reading should be less than
3%. If the receiver sensitivity is to be measured, leave all controls and equipment as they are.
SERVICE CHECK
If the distortion is more than 3%, or maximum audio output is less than 12 watts, make the following checks:
E.
Battery and regulator voltage --- low voltage will cause distortion. (Refer to Receiver Schematic Diagram for voltages.)
F.
Audio Gain (Refer to Receiver Troubleshooting Procedure.)
G. FM Detector Alignment (Refer to Receiver Alignment.)
LBI-31511
STEP 2
USABLE SENSITIVITY
(12 dB SINAD)
If STEP 1 checks out properly, measure the receiver sensitivity as follows:
A. Apply a 1000 microvolt, on-frequency signal modulated by 1000 Hz with 3.0 kHz deviation to J601.
B. Place the RANGE switch on the Distortion analyzer in the 200 to 2000 Hz distortion range position (1000 Hz filter in the circuit). Tune the filter for minimum reading or null on the lowest possible scale (100%, 30%, etc.)
C. Place the RANGE switch SET LEVEL position (filter out of the circuit) and adjust the input LEVEL control for a +2 dB reading on a mid range (30%).
D. Set signal generator output to 0.3 µ
V. Switch the
RANGE control from SET LEVEL to the distortion range Readjust Distortion Analyzer SET LEVEL as required until a 12 dB difference (+2 dB to -10 dB) is obtained between the SET LEVEL and distortion range positions (filter out and filter in).
E.
The 12 dB difference (Signal plus Noise and Distortion to noise plus distortion ratio) is the "usable" sensitivity level. The sensitivity should be less than rated 12 dB
SINAD specifications with an audio output of at least
6 watts (49 Volts RMS across 4.0 ohm receiver load using the Distortion Analyzer as a Voltmeter).
F.
Leave 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 the rated 12 dB
SINAD, check the alignment of the RF stages as directed in the Alignment Procedure.
STEP 3
MODULATION ACCEPTANCE BAND-
WIDTH (IF BANDWIDTH)
If STEPS 1 and 2 check out properly, measure the bandwidth as follows:
A. Set audio to 10% of rated output.
B. Set the Signal Generator output for twice the microvolt reading obtained in the 12 dB SINAD measurement.
C. 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.
D. While increasing the deviation of the Signal Generator, switch the RANGE control from SET LEVEL to distortion range until a 12 dB difference is obtained between the SET LEVEL and distortion range readings
(from +2 dB to -10 dB).
E.
The deviation control reading for the 12 dB difference is the Modulation Acceptance Bandwidth of the receiver. It should be more than
±
7.0 kHz.
SERVICE CHECK
If the Modulation Acceptance Bandwidth test does not indicate the proper width, check the synthesizer frequency and then refer to the Alternate IF Alignment
Procedure.
6
LBI-31511 TRANSMITTER ALIGNMENT
TEST PROCEDURES
These Test Procedures are designed to assist you in servicing a transmitter that is operating -- but not properly. Once a defect is pin-pointed, refer to the Transmitter Troubleshooting Procedure. Before starting, be sure that the transmitter is tuned and aligned to the proper operating frequency.
LBI-31511
(Cont.)
TEST PROGRAMMING
In DELTA-S radios, in which the EEPROM is not custom programmed, the EEPROM may be programmed with the personality similar to the ones shown in Table 1 below. See data on production tag with radio for exact data.
Table 1 - Programmed Test Frequencies
CAUTION
Before bench testing the radio, be sure or the output voltage characteristics of your bench power supply.
To protect the transmitter power output transistors from possible instant destruction, the following input voltages must not be exceeded:
Transmitter unkeyed:
Transmitter keyed (50 ohms resistive load):
20 Volts
18 Volts
Transmitter Keyed (no load or non-resistive load): 14 Volts
These voltages are specified at the normal vehicle battery terminals of the radio and take the voltage drop of standard cables into account. The voltage limits shown for a non-optimum load is for "worst case" conditions. For antenna mismatches likely to be encountered in practice, the actual limit will approach the 18 Volt figure.
Routine transmitter tests should be performed at EIA Standard Test Voltages of (13.6 Vdc for loads of 6 to 16 amperes; 13.4
Vdc for loads of 16 to 36 amperes). Input voltages must not exceed the limits shown, even for transient peaks of short duration.
Many commonly used bench power supplies cannot meet these requirements for load regulation and transient voltage suppression. Bench supplies which employ "brute force" regulation and filtering (such as Lapp Model 73) may be usable when operated in parallel with a 12 volt automotive storage battery.
FREQUENCY
SPLIT
450-470 MHz
470-494 MHz
494-512 MHz
403-430 MHz
CHANNEL
NO.
6
7
4
5
1
2
3
6
7
4
5
1
2
3
5
6
7
3
4
1
2
5
6
7
3
4
1
2
TRANSMIT
FREQUENCY
503.000
509.000
503.000
497.000
494.000
512.000
503.000
413.025
419.025
413.025
407.025
403.000
430.000
414.000
461.025
467.025
461.025
455.025
450.000
470.000
461.000
483.8875
489.8875
483.8875
477.8875
470.000
494.000
485.000
RECEIVE
FREQUENCY
502.975
503.975
502.975
501.975
501.975
511.750
502.750
413.050
414.050
413.050
412.050
403.050
429.750
413.750
461.050
462.050
461.050
460.050
460.025
469.750
460.750
483.050
484.050
483.050
482.050
470.050
493.750
484.750
CHANNEL GUARD
ENC/DEC
71.9
023
---
---
---
71.9
---
71.9
023
---
---
---
71.0
---
71.9
023
---
---
---
71.9
---
71.9
023
---
---
---
71.9
---
CCT
---
---
30 SEC
---
---
---
---
---
---
30 SEC
---
---
---
---
---
---
30 SEC
---
---
---
---
---
---
30 SEC
---
---
---
---
(Cont.)
7
LBI-31511 TRANSMITTER ALIGNMENT
TRANSMITTER FREQUENCY
tor.
ADJUSTMENT
First check the frequency to determine if any adjustment is required. The frequency should be set with a frequency meter or counter with an absolute accuracy that is 5 to 10 times better than the tolerance to be maintained, and with the entire radio as near as possible to an ambient temperature of 25
°
C
(77
°
F).
The oscillator frequency should be set at 25
°
C ambient temperature. In the range of 15
°
C to 40
°
C, if the frequency deviates more than
±
1 PPM, it may be reset to
±
1 PPM, respectively.
NOTE
Refer to Figures 3 and 4 Frequency Correction Fac-
Adjust L352 to set the transmit frequency while monitoring RF output jack J2 through a 30 dB decoupler. If adjusting
L352 does not result in setting transmitter on frequency, remove synthesizer top cover, set L352 two turns from top of coil form, then adjust course frequency control L354 on frequency. Replace cover. This procedure would be necessary if repair/replacing parts in oscillator circuit.
MODULATION LEVEL
ADJUSTMENT
PROCEDURE
1.
Select a center frequency channel. Disable Channel
Guard if present.
2.
Preset R366 fully counterclockwise and R22 on
Channel Guard board (if present) to the center of its range.
3.
Apply a 1 kHz tone at 1.0 VRMS to mic input jack
J603-17. Connect deviation monitor to RF output jack J2 through a 30 dB decoupler. Set DEVIATION
ADJUST R237 for rated deviation.
±
3.75 kHz with
Channel Guard or
±
4.5 kHz without Channel Guard.
4.
Apply a 400 Hz tone through a 100
µ
F capacitor to
J603-15. Set output level to obtain a deviation of
±
2.0
kHz. Note and maintain this voltage level while switching the output frequency to 10 Hz. Adjust REF
OSC Deviation Control R366 starting from the fully clockwise position for
±
2.0 kHz deviation. Remove the modulation.
5.
Select a channel with Channel Guard nearest the center frequency and adjust R22 on the Channel
Guard option board to
±
0.65 kHz (tone or digital
Channel Guard).
ACCESSING CENTER TUNE FREQUENCY
When a radio is factory programmed for less than 16 channels, channel 16 is programmed for transmit and receive center tune frequency.
To access center tune frequency use available control unit and select channel 16.
The MOD ADJUST controls are adjusted to the proper setting before shipment and normally do not require readjustment. This setting permits approximately 75% modulation for the average voice level. The audio peaks which would cause overmodulation are clipped by the modulation limiter. The limiter, in conjunction with the de-emphasis network, instantaneously limits the slope of the audio wave to the modulator, thereby preventing overmodulation while preserving intelligibility.
TEST EQUIPMENT
1.
An audio oscillator (GE Model 4EX6A10)
2.
Deviation Monitor
3.
An output meter or a VTVM
4.
GE Tes t Set Mo de l 4E X3A1 1 T est Cab le
19C850590G1
NOTE
Under normal operation, in radios built prior to January 1989, the microcomputer will not access this channel. The following tests accesses Channel 16 to assure its availability for tuning purposes.
1.
Apply +12 Vdc through a 10K resistor to J604-
3, then turn the radio on. This tells the microcomputer to always access Channel 16.
2.
To select the transmit center tune frequency, press the PTT switch (J601-11). Release the
PTT switch to select the receiver center frequency.
3.
To exit this mode remove power from J604-3 and momentarily remove power from the radio.
AUDIO CHECK
TEST EQUIPMENT REQUIRED
•
Audio Oscillator
•
Oscilloscope
AUDIO AC VOLTAGES
•
•
AC Voltmeter
Deviation Monitor
1.
Connect audio oscillator output across J603-10 (MIC HI) and J603-16 (MIC LO).
SCOPE
SETTING
HORIZONTAL
VERTICAL
SET AUDIO OSCILLATOR AT 1000 Hz WITH OUTPUT OF
1.0 VRMS. MODULATION ADJUSTED FOR 4.5 kHz
DEVIATION. NOTE: AN RMS OR PEAK READING
VOLTMETER WILL READ 1/2 TO 1/3 OF PEAK-TO-PEAK
READINGS.
U301-7
200
µ
SEC/DIV
2 VOLTS/DIV
LBI-31511
C301-1
200
µ
SEC/DIV
2 VOLTS/DIV
AUDIO SENSITIVITY
1.
Connect audio oscillator output across J603-10 (MIC HI) and J603-16 (MIC LO). Adjust output for 1000 Hz at 1.0 VRMS.
2.
Reduce generator output until deviation falls to 3.0 kHz for radios without Channel Guard or to 2.25 kHz for radios with
Channel Guard. Voltage should be less than 120 millivolts.
Figure 3 - Correction Factor in Freq. Setting Figure 4 - Correction Factor in Freq. Setting
8
LBI-31511 TEST CABLE
19C850590G1
(19C850593, Rev. 4)
TRANSMITTER ALIGNMENT
SYNTHESIZER AND TRANSMITTER ALIGNMENT
TEST EQUIPMENT REQUIRED
1.
Watt meter, 50 ohm (capable of measuring 150 watts & 1 watt)
2.
Digital Voltmeter
3.
RF Frequency Counter
4.
RF Voltmeter
5.
Power Supply, 13.8 Vdc regulated
6.
GE Test Set, 4EX3A11 with Test Set Adapter 19C850590G1
7.
Tuning Tool 19B800716P2
PRELIMINARY CHECKS AND ADJUSTMENTS
NOTE
Refer to Figure 5 for location of tuning adjustment controls.
LBI-31511
Connect black plug of GE Test Set to RF Metering jack J101. Connect red system metering plug to J602, system metering.
Set polarity to "+" and voltage range to the 1 volt position (Test 1).
NOTE
Before aligning or making any adjustments to the transmitter, be sure that the output of the 9 volt regulator is set for
9.0
±
0.05 Vdc. Monitor J602-3 with a digital voltmeter and adjust R703.
ALIGNMENT PROCEDURE
Synthesizer TX and RX Vco
The TX and TX VCO voltage adjustments are described by the following steps 1-5. After the lock detect light D713 goes out (step 1 and 3) each VCO is adjusted after selecting the appropriate channel for the maximum reading indicated.
If the light is not out, all readings are meaningless.
As long as the highest operating frequency (VCO voltage) does not exceed the maximum meter reading and the lowest operating frequency (VCO voltage) is not less than the minimum meter reading, the adjustment is proper.
When the two frequency spread is minimal it is acceptable to center tune the VCO voltage between the maximum and minimum meter readings.
If the highest operating frequency is at the low end of the frequency split (example 451.025 MHz on the 450-470 MHz split), the VCO reading may never reach the maximum. Therefore adjust the lowest operating frequency to a VCO voltage above the minimum reading.
9
LBI-31511 TRANSMITTER ALIGNMENT
SYNTHESIZER & TRANSMITTER ALIGNMENT
STEP
METERING POSITION
GE TEST
SET
MULTIMETER
(- TO A-)
TUNING
CONTROL
METER
READING
1.
LED D713 L209 Light out
2.
J202 L209
PROCEDURE
Select the highest frequency transmit channel. Key the transmitter and tune L209 so that the lock detect indicator D713 goes out.
Monitor J202 with a digital voltmeter. Tune L209 for 7.5 Vdc max.
3.
LED D713 C220
Below 7.5
Vdc
Light out
4.
J202 C220
Unkey the transmitter. Select the highest frequency receive channel and tune C220 so that the lock detect indicator D713 goes out.
Monitor J202 with a digital voltmeter. Tune C220 for 7.5 Vdc max.
5.
J202
Below 7.5
Vdc
Above 3.0
Vdc
Test aid for TX and RX Injection
Select the lowest frequency transmit and receive channel. Key the transmitter and check the TX VCO voltage. Unkey the transmitter and check the RX VCO voltage. Both readings should be above 3.0 Vdc.
Monitor TX injection at J102 and RX injection at J451. (Note:
Terminate TX VCO output with 50 ohms to maintain lock with plug removed).
TX injection +5 to +15 dBm
RX injection +5 to +15 dBm
EXCITER/TRANSMITTER POWER AMPLIFIER (Cont.)
LBI-31511
STEP
METERING POSITION
GE TEST
SET
MULTIMETER
(- TO A-)
TUNING
CONTROL
10.
C
(AMPL-3)
J101-8 C10
METER
READING
0.01
11.
C11 500 mw
PROCEDURE
Tune C10 for a dip, 0.01 volts typical. Note, after C11 is tuned, this voltage typically will be 0.5 volts.
Tune C11 for maximum exciter power output as indicated on the wattmeter, connected to J103-2, 4. Exciter output is typically 600 mw.
12.
A
(PA
INPUT)
J1-10 C11
Power is unavailable and the exciter is already connected to the PA, connect the meter to PA board J1. Connect a 150 watt wattmeter to antenna connector
J2. Set the RF Power Adjust control for maximum power (fully clockwise).
Tune C11 for maximum meter reading on J1, position A. Check the meter reading at both ends of the frequency spread. They should be approximately equal. If not adjust C11 accordingly. Set RF power Adjust for rated output power.
13.
A
(PA
INPUT)
J1-10 C11
NOTE
If more than 6.0 MHz (5.0 MHz on 403-430 MHz split) channel spacing is required. Perform steps 13 and 14.
Select the highest frequency channel. Key transmitter and adjust C11 so that output power is slightly above rated power.
14.
C10 Select lowest frequency channel. Key transmitter and adjust C10 so that output power is slightly above rated power. Switch to highest frequency channel and verify rated output power. If necessary repeat this step.
EXCITER TRANSMITTER POWER AMPLIFIER
Preset all four tuning screws in the exciter (C8-C11) so that the tops of the tuning screws are approximately 7 mm above the top of the casting.
Preset L103 so that the core is flush with the top of the coil form.
NOTE
The exciter can be isolated from the rest of the radio for tuning purposes, if desired. To isolate and set up, remove P102 and P103. Connect a (0-1 watt) wattmeter to J103-2, 4. Apply a +7 dBm at 1/3 carrier frequency signal to J102-2, 4.
* Fo is the transmit output frequency at the antenna. The injection frequency is Fo/3 at J102.
REFERENCE OSCILLATOR FREQUENCY
If less than 6.0 MHz (5.0 MHz on 403-430 MHz split) channel spacing is required, select the highest transmit RF frequency.
If 6.0 to 12.0 MHz bandwidth (5.0 to 10.0 MHz on 403-430 MHz split) is required, select center frequency. (Refer to "Accessing
Center Tune Frequency" and complete steps.
STEP
METERING POSITION
GE TEST
SET
MULTIMETER
(- TO A-)
TUNING
CONTROL
6.
J101-10
METER
READING
0.25 V
7.
8.
A
(AMPL-1)
B
(TRIPLER)
B
(TRIPLER)
J101-9 L103
J101-9 C8
-0.45 V
PROCEDURE
Key the transmitter. No tuning required in this step.
Tune L103 for maximum negative meter reading (switch voltmeter for negative reading.)
-0.5 Tune maximum reading.
9.
C
(AMPL-3)
J101-8 C9 2.0 V Tune C9 for maximum meter reading. Stop when maximum is reached.
STEP
METERING POSITION
GE TEST
SET
MULTIMETER
(- TO A-)
TUNING
CONTROL
METER
READING
15.
J2 L352
PROCEDURE
C h a n n e l
O p e ra t in g
Frequency
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. Figures 4 and 5 below show the temperature versus frequency correction curve for the 5 PPM and optional 2 PPM reference osc.
Key the transmitter while monitoring the frequency at the antenna connector J2.
Adjust L352 for the assigned channel freq.
±
225 Hz for a 5 PPM radio (standard) or
±
90 Hz for a 2 PPM radio (optional).
Note: The receiver injection frequency will automatically be correct.
10
LBI-31511 TRANSMITTER ALIGNMENT
Figure 5 - Transmitter/Receiver Tuning & Adjustment Controls
RECEIVER ALIGNMENT LBI-31511
RECEIVER FREQUENCY ADJUSTMENT
(Refer to Transmit Frequency Adjustment, no adjustment of receive frequency is required.)
ALTERNATE IF SWEEP ALIGNMENT
1.
Attach an oscilloscope probe to IF AMP. MTR. (J602-
10). (Refer to Figure 6).
2.
Using an HP8640B signal generator, set with an onchannel frequency, feed a 20 Hz modulating frequency with 12 kHz of deviation into the radio at antenna jack
J2.
3.
Connect a coaxial cable between the AM output of the
HP8640B and the external 10 trigger signal on the scope. Use NORMAL triggering.
4.
DC couple the scope probe and adjust the controls for
0.1V per div. and 2 msec per div.
5.
Adjust the AM output level to make sure the scope is triggering. Adjust the RF input signal level to keep the
IF passband sweep pattern just below saturation (typ. 9
µ
V). After using the vertical and horizontal positioning controls to center the waveform, check for a scope pattern similar to the one below.
SERVICE NOTE: L410, L411, L412, L507 and L508 should be tuned to peak the IF passband, and any ripple should be minimized in the passband.
Figure 6 - Test Set-Up For 20 Hz Double-Trace Sweep Alignment
Figure 7 - Test Set-Up, Audio Output Measurement
11
LBI-31511 RECEIVER ALIGNMENT
ALIGNMENT PROCEDURE (Cont.) RECEIVER ALIGNMENT
TEST EQUIPMENT REQUIRED (Or Equivalent)
1.
GE Test Set 4EX3A11, 4EX8K12, or 20,000 ohmsper-volt millimeter with 1 volt scale
2.
AC Voltmeter
3.
FM Deviation Monitor
4.
Digital Voltmeter
5.
VOM
6.
RF Signal Generator (403-512 MHz)
7.
8.
9.
Frequency counter (Hewlett-Packard 5300B)
Oscilloscope
Audio Isolation Transformer (1:1) 19A116736P1 or equivalent
10. 4 ohm 15 watt resistor
11. Tuning tool 19B800716P2
PRELIMINARY CHECKS AND ADJUSTMENTS
NOTE
Refer to Figure 5 for location of tuning and adjustment controls.
1.
Connect the black plug from the Test Set to the RF metering jack J101. Connect red system metering plug to J602, system metering. Set Test Set to 1 volt scale. A 20,000 ohms-per-volt multimeter may be used when the GE Test Set is not available.
2.
Preset C1-C7 to maximum height above top of tuning nut (10 mm above casting).
3.
Preset L509 to top of coil form and then turn clockwise 11 full turns.
4.
Preset L451 to top of coil form, then turn 15 turns clockwise.
5.
Preset L410, L411, L412, L507 and L508 to top of coil form and then turn clockwise 9 full turns.
6.
Apply power to radio and monitor the regulated 9 volt supply at J602-3. Adjust R703 if necessary to obtain 9
±
0.01 Vdc.
Use a digital multimeter.
NOTE
Before aligning the receiver or making any adjustments to the radio be sure that the output of the 9 volt regulator is set for 9.0
±
0.1 Vdc.
ALIGNMENT PROCEDURE
STEP
METERING POSITION
GE TEST
SET
MULTIMETER
(- TO A-)
TUNING
CONTROL
METER
READING
1.
G
(RX INJ)
J101-4
PROCEDURE
L452
LOCAL OSCILLATOR-BUFFER INJECTION
Peak Select desired channel or center tune frequency. Set Test Set to 1 volt scale and tune L452 for maximum reading on Test Set.
(Cont.)
LBI-31511
STEP
METERING POSITION
GE TEST
SET
MULTIMETER
(- TO A-)
TUNING
CONTROL
3.
J101-4 C7
4.
G
(RX INJ)
H
(RX MIX)
J101-3 C6, C7
L452
METER
READING
Dip
5.
6.
7.
8.
D
(IF AMP)
D
(IF AMP)
D
(IF AMP)
D
(IF AMP)
J602-10
J602-10
J602-10
J602-10
C3
C1, C5
C2, C4
L508, L507
L410, L411 and L412
C1-C5
PROCEDURE
Tune C7 for a dip in Test Set reading.
Peak
MAX
FRONT END ALIGNMENT
Connect RF signal generator to antenna jack J2. Set frequency to desired receive channel or center tune frequency. Set modulation frequency to 1 kHz and deviation to 3 kHz. Set input level to -10 dBm (70 mV).
Tune C3 for maximum indication on meter while reducing the input level of the signal generator as required to keep the IF AMP reading from saturating. (0.6 V typical).
Peak
Tune C6 for maximum. Sequentially retune L452, C6 and C7 until there is no further increase in meter reading.
Peak C1, C5, C2, C4 in sequence while reducing output level of signal generator to prevent saturation.
RF SELECTIVITY
NOTE
Maximum
(See
Procedure)
Maximum
If the IF amplifiers have been aligned using the alternate sweep alignment method, proceed to Step 9.
Select a center frequency channel. Apply an on-frequency signal with 1 kHz modulation to antenna jack J2. Set deviation to 3 kHz. Reduce signal level to approximately 75% of saturated level shown on Test Set meter. While making the following adjustments keep the signal level below saturation.
Tune L508, L507, L412, L411 and L410, in that order, for a peak reading.
Repeak coils until no further improvement in meter reading is noted.
Repeak C1-C5.
9.
10.
L509
R629
FM DETECTOR/AUDIO PREAMPLIFIER
NOTE
The audio output is a balanced bridge circuit and requires all test equipment connected across the speaker leads to the both AC and DC isolated from ground.
0.35 - 0.5
VRMS
Connect test equipment as shown in Figure 5.
Set signal generator output for 1000
µ
V. Set R629 and volume control to the center position. Monitor the speaker outputs (J602-6, 7) with an AC voltmeter. Tune quadrature coil L509 for a peak reading.
Adjust R629, audio preamplifier level for nominal 300 mV RMS at VOL/SQ
HI (J603-14).
(Cont.)
12
LBI-31511
ALIGNMENT PROCEDURE (Cont.)
STEP
METERING POSITION
GE TEST
SET
MULTIMETER
(- TO A-)
TUNING
CONTROL
METER
READING
11.
12.
13.
D
(IF AMP)
D
(IF AMP)
J602-10
J602-10
PROCEDURE
FIXED SQUELCH ADJUSTMENT (8 dB SINAD)
(EARLIER MODELS)
R666 Adjust fixed squelch control R666 fully clockwise (open squelch). Adjust input level of RF Signal Generator to produce a SINAD sensitivity reading of 8 dB. Turn R666 fully counterclockwise (maximum squelch position) to close squelch. Slowly readjust R666 to the position where the squelch just opens. Verify that squelch opens at 8
±
1 dBm.
MULTI-FREQUENCY SPREAD (Multi-Frequency Radios)
(Single Frequency Radio Proceed to Step 16.)
C1-C3 Select a center frequency channel. Apply an on-frequency signal with 1 kHz modulation to antenna jack J2. Set deviation to 3 kHz. Reduce signal level to approximately 75% of saturated level shown on Test Set meter.
Detune C2 three turns clockwise or counterclockwise. Detune in direction that will not exceed maximum or minimum tuning screw height. Tune C1 for a peak. Increase or decrease signal generator level as required to maintain 75% of the saturated signal level. Detune C3 and then tune C2 for a peak. Detune C4 and then tune C3 for a peak.
C4, C5
14.
15.
16.
H
(RX MIX)
D
(IF AMP)
J101-3
J2
C6
C5
C1-C5
Detune C5 clockwise to minimum tuning screw height. Tune C4 for a peak.
Then tune C5 to maximum tuning screw height. Tune C5 for a peak reading.
Select highest channel frequency and note meter reading. Select lowest channel frequency and note reading. Tune C6 slightly to equalize these two readings. If they cannot be equalized tune C6 to improve the channel with lowest reading.
Adjust the frequency of the signal generator to the highest frequency channel. Apply a modulated signal at the 0.35
µ
V level. Measure the SINAD level in accordance with Step 2 of Receiver Test Procedures. If the SINAD reading is 12 dB SINAD or less, tune C5 counterclockwise until the SINAD reading is greater than 12 dB. Switch to the lowest frequency channel and set the signal generator to the lowest frequency channel. Measure the
SINAD level on the distortion analyzer. If the SINAD reading is less than
12 dB, tune C5 clockwise until the SINAD reading is 12 dB. Recheck the sensitivity at the high frequency channel. Readjust C5, if necessary, to keep the sensitivity at the band edges greater than or equal to 12 dB SINAD.
Set signal generator for 12 dB SINAD level. Adjust C1-C5 for best sensitivity.
LBI-31511
13
LBI-31511 RECEIVER AUDIO AND SQUELCH WAVEFORM CHECKS LBI-31511
(19D901350, Sh. 1, Rev. 10)
14
LBI-31511 MECHANICAL LAYOUT LBI-31511
(19D900977, Sh. 1, Rev. 20)
15
LBI-31511 MECHANICAL LAYOUT LBI-31511
(19D900977, Sh. 2, Rev. 14)
16
LBI-31511 INTERCONNECTION DIAGRAM LBI-31511
(19D900980, Sh. 1, Rev. 4)
17
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