Classe Audio CA-301 Service manual

Classé Audio Inc.

Date:
Model Number:

Subject:

July 17, 2007

CA-301
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
IR 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
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]

is intended

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 (RV1) 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 tab 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 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 100Hz, a 1kHz and a 10kHz tone. Check the output with a oscilloscope, on 4

ohms and 8 ohms loads. Take special cares about oscillation and phase corelation 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 CA301 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 CA301 is equipped with four Mosfet 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 Mosfet fuses are located on the control
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 Possible cause

Unit won’t turn on Check connections;

Smoked and/or burned
components

Blown fuses Check for short between fuse and ground;

No output Check connexions;

Unit turn into protection Check for smoked and/or burned components;

Excessive buzz and/or hum Check electrical lines;

Oscillation Check source;

Intermittent signal Check connections;

Check fuses;
Check soft-start circuit;
Check relays;
Check power supply circuits (positive rail, negative rail, Mosfet
supply).
Check for short between components and ground;
Check output transistors;
Check output relays;
Check power supply circuits (positive rail, negative rail, Mosfet
supply).

Check power supply circuits (positive rail, negative rail, Mosfet
supply).

Check output relays;
Check power supply circuits (positive rail, negative rail, Mosfet
supply);
Check output transistors.

Check power supply circuits (positive rail, negative rail, Mosfet
supply);
Check source and load;
Check protection circuit;
Check sensor wires between sensor PCB and control PCB;
Check outputs transistors and Mosfet drivers.

Check for a ground loop in the system.

Check capacitors on main board;
Check 4.7Ω resistor.

Replace shield wires.

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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 4.7Ω resistor and 10Ω soft start resistor, and replace if necessary. Replace any
burnt component or board.

Pins : 1 Base
2 Emitter
Case Collector

You should have these results, if the transistor is good.

MJ21194 (NPN)

Positive lead Negative lead Result

B C Conductive
B E Conductive
C B Infinite
C E Infinite
E B Infinite
E C Infinite

MJ21193 (PNP)

Positive lead Negative lead Result

B C Infinite
B E Infinite
C B Conductive
C E Infinite
E B Conductive
E C Infinite

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