Crown DC-300A - Page 48

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Table of Contents2
List of Illustrations4
Product View5
General Information5
Specifications6
DC 300A Performance Graphs7
Typical Intermodulation Distortion7
Typical Harmonic Distortion7
Typical Frequency Response8
Typical Power Response (Per Channel)8
Typical Phase Response9
Typical Noise Spectrum10
Typical Crosstalk10
Typical Limits of VI Output11
Typical Damping Factor12
Power Efficiency12
Installation & Operation13
Scope13
Unpacking13
Mounting13
Amplifier Protection Mechanisms14
Load Protection Methods14
Graph of VI Operating Range of DC-300A Output14
Fuse Selector Memograph for Loudspeaker Protection15
Relay Controlled Protector with Overload Indicator15
Peak Power Limiting Compressor with Overdrive Indicator15
Turn-On-Transient Muter for Load Protection15
Operating Precautions16
Source Resistance and Damping Factor Vs. Length and Size of Ouput Leads16
Connecting Output Lines17
Connecting Input Lines17
Schematic for Full Range Electrostatic Speaker Connections17
Schematic of Earphone Pad17
Connecting Power18
Operating Controls18
Table for Selection of Input DC Blocking Capacitor18
Low-Pass Filter for Severe RF at Inputs18
Normal Hi-Fi Installation19
Cleaning19
Table of Line Voltage Connections19
Amplifier Operating Controls19
Normal Hi-Fi Hook-Up Diagram20
Circuit Description21
Principles of Operation21
Outuput Circuitry21
Protection Circuits22
LVA, LVA Current Source and Bias Servo Circuits22
Input Circuitry22
Service Procedures23
Service Policies23
Removal of Front Panel and Chassis Cover23
Removal of Chassis Cover Assembly23
Replacement of Components on DCA Main PC Board Assembly24
Replacement of Level Potentiometer (R100, R200)24
Replacement of Power Switch SW124
Replacement of Thermal Switch (SW-2, SW-3)24
Test Equipment25
Test Procedures25
Calibration of Test Equipment25
Replacement of Output and Driver Transistors25
Test Equipment Table26
Test Equipment Complement Chart29
Troubleshooting30
Verify and Identify the Problem30
Visual Inspection30
Turn-On Procedure Troubleshooting31
Input/Output Offset Voltage Check31
Bias Level Check31
Checkout Procedure - 1Khz Input, no Load31
Fuse Blows or + or -60V Appears at Output32
Continuous DC Voltage at Output32
Oscillation at Output with or Without Signal32
Output Unstable When Adjusting Level Pot32
Checkout Procedure - 1Khz Input, with Load33
Checkout Procedure - Protection Circuit Tests33
Clipping Test33
Protection Memory Test33
Checkout Procedure - 20Khz Sine Wave Input34
Checkout Procedure - 10Khz Square Wave Input34
IM (Inter-Modulation) Distortion Test34
Bias Level Check and Adjustment35
Input/Output Offset Adjustment35
Checkout Procedure - 20-20Khz Hum and Noize Test35
Checkout Procedure - Quiescent AC Power Consumption35
Parts Replacement Kit36
Schematics, Parts Lists and Component Locations37
Parts Replacement37
Rear View: Main Chassis38
Front View: Front Panel Removed38
Front Panel Assembly Exploded View39
Parts List: DCA Main Board Assembly40
Parts List: DCA Main Board - Non 2N3773 Outputs41
Heatsink PC Board 7954U Component Location42
Parts List: Heatsink Board Assembly 4120742
Shield Assembly Exploded View43
Parts List: Shield Assembly43
Transformer Assembly Exploded View44
Chassis Exploded View45
Filter Capacity Assembly Exploded View46
Output Coil Assembly Exploded View47

Crown DC-300A - Page 48

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