Classe Audio CA-300 Service manual

Classé Audio Inc.

Date:
Model Number:

Subject:

August 8, 2007

CA-300
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 13
Voltage Change 13
Remote Interface Information 14
Schematics 15

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: [phone] E-mail: [e-mail]

Europe
Phone: [phone] E-mail: [e-mail]

Asia
Phone: [phone] E-mail: [e-mail]

Rest of the World
Phone: [phone] E-mail: [e-mail]

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. Connect the unit to a variable transformer, setted to 0Vac.

3. Turn the bias trimpot (RV102) counter clockwise until a click is heard.

4. Connect the bypass wire to the variable transformer. This bypass is a power cord, modified on the

female side in order to bypass the soft start sequence. It is connected to the line ring on voltage
selector PCB.

5. Slowly raise the voltage to 10Vac, and check positive and negative rails and pre-driver supply. Check

fuses.

6. If one or more supply are not within specifications, return to the troubleshooting guide.

7. Slowly raise voltage until you hear relays click, this point is around 55Vac. Recheck every supply.

8. If one or more supply are not within specifications, return to the troubleshooting guide.

9. Raise voltage to 120Vac. Recheck every supply

10. If every supply is within specifications, unplug the unit and bypass from the variable transformer.

Reconnect only the unit.

11. Report to Calibration and adjusments (section 9) 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.

12. Connect the unit to a load, and to a source using balanced inputs and single ended inputs,

independently.

13. 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.

14. Connect the unit to a small speaker, and short the input. Check for any noise. Perform this step with

single ended inputs and balanced inputs, independently.

15. Put the unit on a burn-in bench, and let it sit for 24 hours, then readjust bias. Let the unit on the burn-

in bench for another 72 hours.

16. Redo steps 11 to 14 before shipping to the customer.

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Protection Modes and Indicators

The front LED shows the status of the amplifier. When starting up normally, the CA300 will show a FLASHING
RED LED for about 15 seconds and if all is normal, the LED will go SOLID RED. If there is a fault, the LED will
go to a FLASHING GREEN LED. The CA300 is equipped, except for some early production models, with four
rails protection fuses. In the event that one or more of these fuses would blow, 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 rail fuses are located on each device 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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