Page 1
640A SERVICE MANUAL
TABLE OF CONTENTS
Safety Precautions & Important Notes 3
Amplifier Bias Set-up
4
Main Assembly BOM (Silver Unit)
5 -“ 7
Input & Tone PCB Schematic (Tone Control)
8
Revised: Input & Tone PCB Schematic (Input Select) 9
Input & Tone PCB Layout (Top Side) 10
Input & Tone PCB Layout (Bottom Side)
11
Input & Tone PCB BOM
12
Front Panel Schematics
13
Front Panel PCB Layout (Top Side)
14
Front Panel PCB Layout (Bottom Side)
15
Front Panel PCB BOM
16
Power Amp Schematic (Power Supply)
17
Power Amp Schematic (Protection)
18
Power Amp Schematic (Left Channel)
19
Power Amp Schematic (Right Channel)
20
Power Amp PCB Layout (Top Side)
21
Power Amp PCB Layout (Bottom Side)
22
Power Amp PCB BOM
23 -“ 25
Speaker Output Schematic
26
Speaker Output PCB Layout (Top Side)
27
Speaker Output PCB Layout (Bottom Side)
28
Speaker Output PCB BOM
29
Mains Input Schematic
30
Mains Input PCB Layout (Top Side)
31
Mains Input PCB Layout (Bottom Side)
32
Mains Input PCB BOM
33
IC Pin Layout Details
34 -“ 38
Silver / Black Difference BOM
39
Amended Input Circuit Schematic (Jan 2004)
40
Amended Input Circuit Schematic (March 2005)
41
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SA FE TY P R EC AU TIO NS & I M PO RTA N T N OTES
1. Check that the rear of the product indicates the correct supply voltage \
for you area.
2. The lighting flash with the arrowhead within an equilateral
triangle is intended to alert the user or service agent to the
presence of dangerous voltages within the product enclosure
that may be of sufficient magnitude to constitute a risk of
electric shock to persons.
3. The exclamation point within an equilateral triangle is
intended to alert the user or service agent to the presence of
important operating and maintenance (Servicing) instructions
in the literature accompanying the appliance.
4. This product complies with EEC Low Voltage (73/23/EEC) and
Electromagnetic Compatibility (89/336/EEC) Directives when used and
serviced in accordance with this manual. For continued compliance all
components marked safety and EMC critical must only be replaced by
Cambridge Audio approved parts.
5. Any unauthorised design alterations or additions will void the
manufacturers warranty; furthermore the manufacturer cannot accept
responsibility for personal injury or property damage resulting therefrom.
6. When servicing, care should be taken to observe the original routing \
and dressing of the leads and it should be confirmed that they have been\
returned to normal after re-assembly.
Notes on chip component replacement
Never reuse a component that has been removed from a PCB
Notice that the minus side of a tantalum capacitor may be damaged by hea\
t
C O PY RIG HT N OTIC E.
© 2005 Audio Partnership PLC. All rights reserved.
Cambridge Audio and Azur are registered trademarks of Audio Partnership \
PLC. This document
may not be reproduced, distributed, transmitted, displayed, published, or broadcast without the
express written prior permission of Audio Partnership PLC.
Alteration or removal of any trademark, copyright, or other notice from this content is prohibited.
Information provided in this document is provided solely for the use of official service agents in
repairing and servicing Audio Partnership PLC products.
