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TABLE OF CONTENTS
(Cont.)
4.3.6.1
Operation of Phase Lock Loops
~25
~25
4.3.6.2
Digital Control
4.3.6.3
oscillator Control
~29
4.3.7
Second LO and BFO Generator, A8
~33
4.3.7.1
Internal/External Reference Frequenc;:y
~33
4.3.7.2
Internal Mode
~33
4.3.7.3
External Mode
~35
4.3.7.4
Second Local Oscillator
~.35·
...
4'.3.7.5
Beat t:requency Oscillator (BFO)
.4-37:
4.3.8
Receiver Control Section
q...;.41
4.3.8.1
Microcomputer Board, A6A2
4-48
4.3.8.2
Serial Asynchronous Interface, A6A 1
4-53
4.3·.9
Power Supply, Ala
~57
4.3.9.1
DC Power Supply
4-57
SECTION V. MAINTENANCE
5.1
General
5-1
5.2
Preventive Maintenance
5-1
5.2.1
Inspection for Damage or Wear
5-1
5.2.2
Cleaning and Lubrication
5-2
5.3
Maintenance Support Equipment
5-3
5.4
RA6790/GM Operational Checkout and Fault Isolation
5-4
Procedures
5.4.1
Initial Check
5-5
5.4.2
BITE Check
5-6
5.4.3
Al Low Pass Filter Check
5-9
5.4.4
A4 Main IF / AF Audio Check
5-10
5.4.5
A5 ISB Audio Check
5-10
5.4.6
A6A 1 Remote Serial Asynchronous Interface Check
5-10
5.5
RA6790/GM Performance Tests
5-10
5.5.1
Frequency Tuning
5-12
5.5.2
Frequency Display
5-12
5.5.3
Frequency Stability
5-13
5.5.4
Frequency Calibration Resolution
5-13
5.5.5
RF Gain Control
5-13
5.5.6
Final IF Frequency
5-13
5.5.7
Fixed/Variable BFO Operation
5-14
5.5.8
Audio Output Power
5-15
5.5.9
Audio Distortion
5-15
5.5.10
Operation After Restoration of Power
5-15
5.6
Board Level Fault Isolation
5-16
5.7
Receiver Assembly and Disassembly Procedures
5-16
5.7.1
Preliminary Procedure
5-16
5.7.2
Top and Bottom Covers
5-16
5.7.3
Al Module Removal
5-17
5.7.4
Al Module Installation
5-17
5.7.5
A2 Module Removal
5-19
5.7.6
A2 Module Installation
5-19
5.7.7
Module Removal
5-19
5.7.8
A3 Module Installation
5-20
5.7.9
A4 Module Removal
5-20
iii
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