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1、PRO-SVR_LEGACY Page 1 of 11 Date: August 27, 2007 Model Number: DR-8 Class Audio Inc. Subject: Service manual Class Audio, Inc. 5070 Franois Cusson Lachine, Qubec Canada H8T1B3, RadioFans.CN PRO-SVR_LEGACY Page 2 of 11 Table of Contents Introduction 3 Important Notes on Servicing 3 Ordering Replacem
2、ent 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 Fuses 10 Voltage Change 10 Schematics 12 The contents of this document as well as the files associated with it conta
3、in confidential information that is proprietary to Class 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 Class Audio Incorp
4、orated. RadioFans.CN PRO-SVR_LEGACY Page 3 of 11 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
5、 the user to the presence of uninsulated dangerous voltage within the products 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 an
6、d maintenance (servicing) instructions. Class 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: Europe Phone: 44 (0) 1903 221 700 E-m
7、ail: Asia Phone: (852) 2790 8903 E-mail: classebwgroup.hk Rest of the World Phone: (514) 636-6384 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 Class. 3.A
8、LWAYS use Class 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 replac
9、ement part orders and the Class order number when returning defective parts for credit. RadioFans.CN PRO-SVR_LEGACY Page 4 of 11 Block diagrams RadioFans.CN PRO-SVR_LEGACY Page 5 of 11 Start Up Procedure When receiving a unit, an assiduous visual inspection must be performed. Do not connect the unit
10、 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 co
11、ndition. 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.
12、 Turn the bias trimpot (R16) counter clockwise until a click is heard. 4. Slowly raise the voltage to 10Vac, and check positive and negative rails and pre-driver supply. Check fuses. 5. If one or more supply are not within specifications, return to the troubleshooting guide. 6. Slowly raise voltage
13、until you hear relays click, this point is around 55Vac. Recheck every supply. 7. If one or more supply are not within specifications, return to the troubleshooting guide. 8. Raise voltage to 120Vac. Recheck every supply 9. Report to Calibration and adjusments to adjust bias and DC offset. Note that
14、 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. 10. Connect the unit to a load, and to a source using balanced inputs and single ended inputs, independently. 11. Perform a test with a 200Hz, a 2kHz and a 20k
15、Hz 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. 12. Connect the unit to a small speaker, and short the input. Check for any noise. Perform this step with single en
16、ded inputs and balanced inputs, independently. 13. 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. 14. Redo steps 10 to 13 before shipping to the customer. RadioFans.CN PRO-SVR_LEGACY Page 6 of 11 Protection M
17、odes and Indicators The protection circuit on the DR-8 is triggered by a high DC offset condition. This is the only protection available on this unit. Therefore, extra precautions should be taken to make sure the unit is OFF before manipulating the connections. When a high DC offset is present at th
18、e output, the protection circuit opens both output relays, even if the condition is only present on one channel. If the relays are intermittently clicking, DC offset should be monitored for a long period of time, to make sure DC offset caused that condition, and not the protection circuit itself tha
19、t is running out of specifications. RadioFans.CN PRO-SVR_LEGACY Page 7 of 11 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/o
20、r 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,
21、 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, Mosfe
22、t 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
23、 board; Check 4.7? resistor. Intermittent signal Check connections; Replace shield wires. Intermittent / fast output relay click Check DC offset before relays; Check relays; Check capacitors on protection circuit. RadioFans.CN PRO-SVR_LEGACY Page 8 of 11 Output Transistors Testing and Replacement PL
24、EASE 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 tr
25、ansistors, 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
26、channel. When replacing blown output transistors, you must also replace positive and negative Mosfet drivers and bias transistor. Carefully inspect 4.7? resistor and 10? soft start resistor, and replace if necessary. Replace any burnt component or board. Pins : 1 Base 2 Emitter Case Collector You sh
27、ould have these results, if the transistor is good. MJ15024 (NPN) Positive lead Negative lead Result B C Conductive B E Conductive C B Infinite C E Infinite E B Infinite E C Infinite MJ15025 (PNP) Positive lead Negative lead Result B C Infinite B E Infinite C B Conductive C E Infinite E B Conductive
28、 E C Infinite RadioFans.CN PRO-SVR_LEGACY Page 9 of 11 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. Connect a multimeter to one of the emitter resistor lea
29、ds and set the multimeter to mV scale. 2. Turn trimpot R16 counterclockwise until it reaches 0?. A click should be heard. 3. Turn on amplifier, and let it warm up for 15 minutes on idle. 4. Adjust trimpot R16 to get a 14mV reading. 5. Let the amplifier warm up for a 24 hours period with signal and l
30、oad. 6. Remove signal and load, and reconnect the multimeter, setted to mV scale, to one of the emitter resistor leads. 7. Readjust R16 to 18mV 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.
31、 1. Connect a multimeter to the output binding posts and set the multimeter to mV scale. 2. Adjust trimpot R5 in order to reach 0mV. It is easier to turn the trimpot turn at a time, and let DC offset stabilize in order to get an accurate reading. 3. A tolerance of 1mV is acceptable. RadioFans.CN PRO
32、-SVR_LEGACY Page 10 of 11 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 HOL
33、DERS 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: 5A slo-blo, Classe part number MDL-5A 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 re
34、ar panel. 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. To convert from 120VAC to 220 VAC. 1. Remove ONE of the wires
35、of group 1 going to the power switch (see fig. 1 for details). 2. Cut group 2 and separate all the wires at the junction where they joined the single wire going to the AC receptacle at the rear of the amplifier. 3. With an ohmmeter, test for continuity between one of the wires removed from group 1 a
36、nd each wire of group 2. 4. Cut off and insulate the wire of group 2 which is continuous with the wire of group 1. 5. Test for continuity between the same wire of group 1 and both wires of group 3 or both wires of group 4 (do not separate the wires of each group). 6. Whichever group is continuous wi
37、th the wire from group 1 should be joined to the wire going to the AC receptacle at the rear of the amplifier (formely attached to group 2) Solder and insulate carefully. 7. Reinsulate the non-continuous group and leave it as it was. 8. Join together the wires from group 1 (the same wires you first
38、removed and have tested with) to the non-continuous wire of group 2 (previously tested). Solder and insulate carefully. 9. Replace the power switch with a 250v one. 10. Remove the varistor, and replace with a 250v one 11. Test the amplifier with a autotransformer. RadioFans.CN PRO-SVR_LEGACY Page 11 of 11 Voltage Change Fig. 1 120v AC wiring Fig. 2 220v AC wiring RadioFans.CN RadioFans.CN RadioFans.CN
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