Classé Audio Inc.
Date:
August 20, 2007
Model Number:
CAV-75
Subject:
Service manual
Classé Audio, Inc. 5070 François Cusson Lachine, Québec Canada H8T1B3, www.classeaudio.com
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Table of Contents
Introduction 3
Important Notes on Servicing 3
Ordering Replacement Parts 3
Block Diagrams 4
Start up Procedure 5
Protection Modes and Indicators 6
Troubleshooting Guide 7
Output Transistors Testing and Replacement 8
Calibrations and Adjustments 9
Parts List 10
Updates 11
Fuses 12
Voltage Change 12
Remote Interface Information 13
Schematics 14
The contents of this document as well as the files associated with it contain confidential information that is proprietary to Classé Audio
Incorporated and are intended solely for the purpose of servicing product. No part of its contents may be used, copied, disclosed, or conveyed to
any party in any manner whatsoever without prior written permission from Classé Audio Incorporated.
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Introduction
Please read this manual carefully before commencing servicing!
Only qualified and authorized personnel should attempt to service this product.
The lightning flash with arrowhead symbol, within an equilateral triangle, is intended
to alert the user to the presence of uninsulated dangerous voltage within the
product’s enclosure that may be of sufficient magnitude to constitute a risk of electric
shock to persons.
The exclamation point within an equilateral triangle is intended to alert the user to
the presence of important operating and maintenance (servicing) instructions.
Classé has a global product support network. For product assistance or to order replacement parts please
contact your nearest service center always quoting the unit serial number.
North America
Phone: (978) 664-2870 E-mail: classe@bwgroupusa.com
Europe
Phone: 44 (0) 1903 221 700 E-mail: classe@bwgroup.com
Asia
Phone: (852) 2790 8903 E-mail: classe@bwgroup.hk
Rest of the World
Phone: (514) 636-6384 E-mail: cservice@classeaudio.com
Important Notes on Servicing
1. ALWAYS observe ESD precautions when handling electronic modules or PCBAs.
2. NEVER exchange boards with a different revision number, unless authorized by Classé.
3. ALWAYS use Classé original replacement parts. The use of generic parts may void the warranty of
the unit.
Ordering Replacement Parts
There may be a delay in processing incomplete requests. Please be sure to include all required information.
Remember to quote the serial number of the unit on all replacement part orders and the Classé order number
when returning defective parts for credit.
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Block diagrams
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Start Up Procedure
When receiving a unit, an assiduous visual inspection must be performed. Do not connect the unit without
analysing the symptoms reported by the customer and the results of the inspection.
Using the troubleshooting guide, find the problem and proceed to the repair. Once this step is done, follow
these steps, known as the start-up procedure, to ensure that everything in the unit is in working condition.
1. Proceed with a post repair visual inspection. Take the time to check if every wire is reconnected
properly, every screw is bolted on, no soldering and/or metal residues lying in the unit, every fuse has
been replaced, etc.
2. Turn the bias trimpots, counter clockwise for channels 2, 4, 6 and clockwise for channels 1, 3, 5, until a
click is heard.
3. Since there is no soft-start sequence of the CAV-75, it is impossible to us a bypass to perform a slow
start up.
4. Connect Main supply, and turn on the unit.
5. If one or more supply are not within specifications, return to the troubleshooting guide.
6. If every supply is within specifications, report to calibration and adjusments to adjust bias and DC
offset. Note that bias can be adjusted to 14mV, and the following tests can be performed before the
unit is send to the burn-in bench for a 24 hours warm-up.
7. Connect the unit to a load, and to a source using single ended inputs.
8. Perform a test with a 200Hz, a 2kHz and a 20kHz tone, both sinus wave and square wave. Check the
output with a oscilloscope, on 4 ohms and 8 ohms loads. Take special cares about oscillation and phase
correlation between channels.
9. Connect the unit to a small speaker, and short the input. Check for any noise.
10. Put the unit on a burn-in bench, and let it sit for 24 hours, then readjust bias. Let the unit on the burnin bench for another 72 hours.
11. Redo steps 7 to 11 before shipping to the customer.
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Protection Modes and Indicators
The front LED shows the status of the amplifier (ON or OFF). Unlike other Classé amplifiers, when starting up
a CAV75, the front LED will not show a flashing pattern, since there is no soft start sequence. The only
protection available on a CAV75 consists of rail and mosfet fuses. If there is a fault, one or more fuses will
blow, showing a faulty component. The technician will first need to identify and cure the cause of failure
(please report to troubleshooting guide). When the cause has been identified, disconnect the unit from the
system including the AC power. Remove the top cover and look for damaged or burned components. If no
other components than the fuses appear to be damaged, the technician can then replace the broken fuses
with the same value and rating (please report to fuses section). The fuses are located on the capacitor board.
When replacing fuses, please make sure that the fuse holder are holding the fuses very tightly. A loose fuse
holder can translate into distortion on top of the signal.
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Troubleshooting Guide
Symptom
Unit won’t turn on
Smoked and/or burned
components
Blown fuses
No output
Unit turn into protection
Excessive buzz and/or hum
Oscillation
Intermittent signal
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Possible cause
Check connections;
Check fuses;
Check relays;
Check power supply circuits (positive rail, negative rail,
supply).
Check for short between components and ground;
Check output transistors;
Check output relays;
Check power supply circuits (positive rail, negative rail,
supply).
Check for short between fuse and ground;
Check power supply circuits (positive rail, negative rail,
supply).
Check connexions;
Check output relays;
Check power supply circuits (positive rail, negative rail,
supply);
Check output transistors.
Check for smoked and/or burned components;
Check power supply circuits (positive rail, negative rail,
supply);
Check source and load;
Check protection circuit;
Check sensor wires between sensor PCB and control PCB;
Check outputs transistors and Mosfet drivers.
Check electrical lines;
Check for a ground loop in the system.
Check source;
Check capacitors on main board;
Check 4.7ƻ resistor.
Check connections;
Replace shield wires.
Mosfet
Mosfet
Mosfet
Mosfet
Mosfet
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Output Transistors Testing and Replacement
PLEASE NOTE THAT THESE TESTS ARE ONLY EFFECTIVE ON BIPOLAR TRANSISTORS.
DO NOT PERFORM THESE TESTS ON MOSFET DEVICES, AS THEY ARE LIKELY TO
BECOME SHORT DURING THE TEST.
You should check all pin combinaisons, as there is a chance that only one side of the transistor is short. When
replacing outputs transistors, the technician should first disconnect both outputs and main board to check if
the blown outputs were caused by a faulty component on the amplifier’s base. Blown output transistors should
be replaced by kits, not individually. These kits contains matched transistors for both rails of one channel.
When replacing blown output transistors, you must also replace positive and negative Mosfet drivers and bias
transistor. Carefully inspect 4.7ƻ resistor and replace if necessary. Replace any burnt component or board.
Pins : 1
2
3
Base
Collector
Emitter
You should have these results, if the transistor is good.
2SC3263 (NPN)
Positive lead
B
B
C
C
E
E
Negative lead
C
E
B
E
B
C
Result
Conductive
Conductive
Infinite
Infinite
Infinite
Infinite
Negative lead
C
E
B
E
B
C
Result
Infinite
Infinite
Conductive
Infinite
Conductive
Infinite
2SA1294 (PNP)
Positive lead
B
B
C
C
E
E
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Calibrations and Adjustments
Bias adjustment:
Note: Bias adjustment should be made without any load connected to the amplifier’s output, and no signal
connected to the amplifier’s input.
1. Since it is impossible to connect a multimeter to both emitter’s resistors in order to measure and adjust
bias without disassembling the heatsink from the chassis, we provided a test point to ease the bias
procedure. It is located near the bias trimpot.
2. Connect the positive probe of a millivoltmeter to the test point and the negative probe to the positive
speaker post of the channel to be adjusted.
3. Turn channel 2, 4, 6 trimpots counterclockwise and channel 1, 3, 5 trimpots clockwise until it reaches
0ƻ. A click should be heard.
4. Turn on amplifier, and let it warm up for 15 minutes on idle.
5. Adjust trimpot to get a 14mV reading.
6. Let the amplifier warm up for a 24 hours period with signal and load.
7. Remove signal and load, and reconnect the multimeter.
8. Readjust to 20mV.
DC offset:
Note: DC offset adjustment should be made without any load connected to the amplifier’s output, and no
signal connected to the amplifier’s input.
On these units, DC offset can’t be adjusted. Measure DC offset using a voltmeter connected to the output
posts, scale setted to mV. DC offset should be less than 10mV.
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Parts List
This is not a detailed part list. It is a list of major chassis parts and PCBs. If you need to order a specific part,
please contact Classe Audio with the part location, PCB number, and model and serial number of the unit.
If you need a complete PCB, please replace the (x) in the Classe part number with the revision number printed
on the board.
Parts
B01CX
B01GX
B0D3X
B0D1X
B0D4X
B0D2X
B01DX
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Complete
Complete
Complete
Complete
Complete
Complete
Complete
PCB,
PCB,
PCB,
PCB,
PCB,
PCB,
PCB,
Description
power switch
filter
capacitor
heatsink
supply
amplifier
remote
Classe part number
B01CXR(x)
B01GXR(x)
B0D3XR(x)
B0D1XR(x)
B0D4XR(x)
B0D2XR(x)
B01DXR(x)
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Updates
1. On board B0D1X (3 PCBs), replace R110 and R210 with Classe part number A211-1308.
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Fuses
EXTRA PRECAUTIONS SHOULD BE TAKEN WHEN REPAIRING, MODIFYING, OR
TROUBLESHOOTING IN THE POWER SUPPLY AREA. UNIT MUST BE DISCONNECT
FROM MAIN SOURCE AND CAPACITORS MUST BE DISCHARGED USING A 100W
INCANDESCENT BULB.
WHEN REPLACING FUSES, PLEASE MAKE SURE THAT THE FUSE HOLDERS ARE
HOLDING THE FUSES VERY TIGHTLY. A LOOSE FUSE HOLDER CAN TRANSLATE INTO
DISTORTION ON TOP OF THE SIGNAL.
Main fuses:
For 100 – 120v units: 6A slo-blo, Classe part number MDL-6A
For 220 – 240v units: 4A slo-blo, Classe part number MDL-4A
The main fuse is located at the back of the unit, on the rear panel.
Control board fuse: 0.50A, Classe part number 225.500
The control board fuse is located on top of the supply board (B0D4X)
Mosfet fuses: 0.75A, Classe part number 225.750
The Mosfet fuses are located on top of the capacitors board (B0D3X)
Rail fuses: 3.15A, Classe part number GDB-3.15A
The rail fuses are located on top of the capacitors board (B0D3X)
Voltage Change
EXTRA PRECAUTIONS SHOULD BE TAKEN WHEN REPAIRING, MODIFYING, OR
TROUBLESHOOTING IN THE POWER SUPPLY AREA. UNIT MUST BE DISCONNECT
FROM MAIN SOURCE AND CAPACITORS MUST BE DISCHARGED USING A 100W
INCANDESCENT BULB.
1. Set the jumper position according to the table below.
2. Replace the varistor, according to new line voltage, following Classe’s recommendations. If varistor is
not available, remove old varistor and leave it empty.
Mains
100VAC
120VAC
220VAC
240VAC
Mains
100/120VAC
220/240VAC
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Jumper positions, main transformer
Jumper 1
Jumper 2
Jumper 3
A
E
F
A
C
D
B
E
B
D
-
Position 1
In
Out
Jumpers, auxiliary transformer
Position 2
Position 3
Out
Out
Out
In
Varistor
221
221
391 / 441
391 / 441
Position 4
Out
Out
Position 5
In
Out
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Remote Interface Information
The CAV75 can be turned on or off using an simple interface connected to the Remote jack, located at the
back of the unit.
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