Classe Audio CAM-350 User manual

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Date: August 16, 2007
Model Number: CAM-350
Classé Audio Inc. 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
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, 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: [email protected]
Europe
Phone: [phone] E-mail: [email protected]
Asia
Phone: [phone] E-mail: [email protected]
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 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 CAM350 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 CAM350 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;
Check fuses;
Check soft-start circuit;
Check relays;
Check power supply circuits (positive rail, negative rail, Mosfet
supply).
Smoked and/or burned
components
Check for short between components and ground;
Check output transistors;
Check output relays;
Check power supply circuits (positive rail, negative rail, Mosfet
supply).
Blown fuses Check for short between fuse and ground;
Check power supply circuits (positive rail, negative rail, Mosfet
supply).
No output Check connexions;
Check output relays;
Check power supply circuits (positive rail, negative rail, Mosfet
supply);
Check output transistors.
Unit turn into protection Check for smoked and/or burned components;
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.
Excessive buzz and/or hum Check electrical lines;
Check for a ground loop in the system.
Oscillation Check source;
Check capacitors on main board;
Check 4.7Ωresistor.
Intermittent signal Check connections;
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 4.7Ωresistor and 10Ωsoft start resistor, and replace if necessary. Replace any
burnt component or board.
Pins : 1 Base
2 Collector
3 Emitter
You should have these results, if the transistor is good.
2SC3264 (NPN)
Positive lead Negative lead Result
B C Conductive
B E Conductive
C B Infinite
C E Infinite
E B Infinite
E C Infinite
2SA1295 (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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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. On positive heatsink, connect a multimeter to R111 leads and set the multimeter to mV scale.
2. Turn trimpot R104 counterclockwise until it reaches 0Ω. A click should be heard.
3. Turn on amplifier, and let it warm up for 15 minutes on idle.
4. Adjust trimpot R104 to get a 10mV reading.
5. Repeat procedure with negative heatsink.
6. Let the amplifier warm up for a 24 hours period with signal and load.
7. Remove signal and load, and reconnect the multimeter, setted to mV scale, to R112 leads.
8. Readjust R104 to get a 12mV reading.
9. Repeat procedure with negative heatsink.
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 Description Classe part number
B1DAX Complete PCB, power switch B1DAXR(x)
B1D1X Complete PCB, heatsink B1D1XR(x)
B02AX Complete PCB, amplifier B02AXR(x)
B1B3X Complete PCB, control B1B3XR(x)
B1B1X Complete PCB, capacitors B1B1XR(x)
B016X Complete PCB, AC B016XR(x)
B258X Complete PCB, input B258XR(x)
B019X Complete PCB, sensor B019XR(x)
B01GX Complete PCB, filter B01GXR(x)
B1B2X Complete PCB, supply B1B2XR(x)

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Updates
1. On board B1D1X (both PCBs), replace R104 with Classe part number 3299X-1-202.
2. On board B1D1X (both PCBs), replace D101 and D103 with Classe part number 1N5333B.
3. On board B1B3X, replace P011XR02 to 040AR3, and drop rail voltage sensor from 500mV to 250mV.
4. Add a jumper from GND post on B1B1X PCB to relay GND on B1B3X PCB.

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Fuses
EXTRA PRECAUTIONS SHOULD BE TAKEN WHEN REPAIRING, MODIFYING, O
R
TROUBLESHOOTING IN THE POWER SUPPLY AREA. UNIT MUST BE DISCONNEC
T
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: 10A slo-blo, Classe part number MDA-10A
For 220 – 240v units: 4A slo-blo, Classe part number MD
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 (B1B2X)
Mosfet fuses: 0.75A, Classe part number 225.750
The Mosfet fuses are located on top of the supply board (B1B2X)
Voltage Change
EXTRA PRECAUTIONS SHOULD BE TAKEN WHEN REPAIRING, MODIFYING, O
R
TROUBLESHOOTING IN THE POWER SUPPLY AREA. UNIT MUST BE DISCONNEC
T
FROM MAIN SOURCE AND CAPACITORS MUST BE DISCHARGED USING A 100W
INCANDESCENT BULB.
1. Set the primary wires of the main transformer as described 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.
3. Set the jumpers accordingly on the auxiliary transformer located at the back of the unit on the top
main board on the left-hand side of the auxiliary transformer (see tables below)
Primary wires, main transformer
Mains X1 X2 X3 X4 X5 X6 X7 X8 Varist
or
100VAC Grey Yellow Blue Black Orange White - - 130
120VAC Blue Black Grey Yellow Orange White - - 130
220VAC - Yellow Grey Black - White Blue Orange 250
240VAC - Black Grey Yellow - White Blue Orange 250
Jumpers, auxiliary transformer
Mains Position 1 Position 2 Position 3 Position 4 Position 5
100/120VAC In Out Out Out In
220/240VAC Out Out In Out Out

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IR Interface Information
Press and hold: AMP + LINE 1 = Turns on Amplifier # 1
AMP + LINE 2 = Turns on Amplifier # 2
AMP + LINE 3 = Turns on Amplifier # 3
AMP + BAL 1 = Turns on Amplifier # 4
AMP + BAL 2 = Turns on Amplifier # 5
AMP + BAL 3 = Turns on Amplifier # 6
J3 J2 J1 J0 ADDRESS RC Button Auto ON Note
X X X X 0 Amp1 No QC setting
X X X Out 1 Amp2 No
X X Out X 2 Amp3 No
X X Out Out 3 Amp4 No
X Out X X 4 Amp5 No
X Out X Out 5 Amp6 No
X Out Out X 0 Amp1 No
X Out Ot Out 0 Amp1 Yes On with AC
Out X X X 0 DC No
Out X X Out 1 DC No
Out X Out X 2 DC No
Out X Out Out 3 DC No
Out Out X X 4 DC No
Out Out X Out 5 DC No
Out Out Out X 0 DC No
Out Out Out Out 0 DC Yes On with AC

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