DR-9 Service manual
Contents
1. Date August 27 2007 C LASS E Model Number DR 9 Class Audio Inc Subject Service manual Class Audio Inc 5070 Francois Cusson Lachine Qu bec Canada H8T1B3 www classeaudio com PRO SVR_LEGACY Page 1 of 11 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 Fuses 10 Voltage Change 10 Schematics 12 The contents of this document as well as the files associated with it contain 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 Incorporated PRO SVR_LEGACY Page 2 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 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 persons2. The exclamation point within an equilateral triangle is intended to alert the user to the presence of important operating and 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 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 Class 3 ALWAYS 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 replacement part orders and the Class order number when returning defective parts for credit PRO SVR_LEGACY Page 3 of 11 Output and Heatsink Output and Heatsink Protection Supply and Soft start Input board Block diagrams DC main supply DC auxiliary supply Signal Output ACmains Vo
3. Infinite PRO SVR_LEGACY Page 8 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 See 7 Connect a multimeter to one of the emitter resistor leads and set the multimeter to mV scale Turn trimpot R16 counterclockwise until it reaches 0Q A click should be heard Turn on amplifier and let it warm up for 15 minutes on idle Adjust trimpot R16 to get a 14mV reading Let the amplifier warm up for a 24 hours period with signal and load Remove signal and load and reconnect the multimeter setted to mV scale to one of the emitter resistor leads 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 1 2 3 Connect a multimeter to the output binding posts and set the multimeter to mV scale Adjust trimpot R5 in order to reach OmV It is easier to turn the trimpot 2 turn at a time and let DC offset stabilize in order to get an accurate reading A tolerance of imV is acceptable PRO SVR_LEGACY Page 9 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 US
4. ING A 100W INCANDESCENT BULB HOLDING THE FUSES VERY TIGHTLY A LOOSE FUSE HOLDER CAN TRANSLATE INTO WHEN REPLACING FUSES PLEASE MAKE SURE THAT THE FUSE HOLDERS ARE DISTORTION ON TOP OF THE SIGNAL Main fuses For 100 120v units 8A slo blo Classe part number MDL 8A For 220 240v units 6A slo blo Classe part number MDL 6A The main fuse is located at the back of the unit on the rear 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 Using a ohmmeter locate and label each of the four transformer windings Rewire the terminal block according to the schematic in fig 1 Replace varistor with correct value PRO SVR_LEGACY Page 10 of 11 Voltage Change DR 9 primary SCHEMATIC TERMINAL BLOCK WHITE Yritow ui EB a BLACK WHITE WHITE 3 WHITE Per ow wwe WHITE WHITE WHITES BLACK BLACK 3 YELLOW Y WHITE 2 WHITE 4 WHITE BLACK WHITE SLACK 3 s AMan 2 2 0 votrs WHITE 3 wHirE 2 Ro BLACK YELLOW Z WHITE 4 WHITE 34 wie Z BLACK YEuowz WHITE BLACK 3 lt gt YEttow Y TWiST TOGETNER SOLDEE AMD Covel WiTH MEAT SHENK TUBING OR ELECTRICAL TAPE BEND AROUND BASE OF TRANSFORMER NOTE Do not connect unused winding
5. ing out of specifications PRO SVR_LEGACY Page 6 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 supply Mosfet 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 supply Mosfet Blown fuses Check for short between fuse and ground Check power supply circuits positive rail negative rail supply Mosfet No output Check connexions Check output relays Check power supply circuits positive rail negative rail supply Check output transistors Mosfet Unit turn into protection 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 Mosfet 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 7Q resistor Intermittent signal Check connections Replace shield wires Intermittent fast output relay click Check DC off
6. ltage selector Noise filter PRO SVR LEGACY Page 4 of 11 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 bg WON Du 11 12 13 14 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 Connect the unit to a variable transformer setted to OVac Turn the bias trimpot R16 counter clockwise until a click is heard Slowly raise the voltage to 10Vac and check positive and negative rails and pre driver supply Check fuses If one or more supply are not within specifications return to the troubleshooting guide Slowly raise voltage until you hear relays click this point is around 55Vac Recheck every supply If one or more supply are not within specifications return to the troubleshooting guide Raise voltage to 120Vac Recheck every supply Report to Calibration and adjusments to adjust bias and DC offset Note that bias can be adjusted to 14mV and
7. s unless specified Isolate and wrap them at base of transformer Fig 1 120v AC wiring PRO SVR_LEGACY Page 11 of 11 ee cz O 01UF 100 1N6148 Di A AA 1000UF 53Y 184148 D2 gt POSDRIVE ct MOUNTED ON UPPER TEE BAR MIDDLE DEVICE Rt FDBK S 0UF 100 Ree SOS ee RS el CG OCC ares sas 200K gt NECORIVE 47UF 200V LEVEL FRIMPOT MOUNTED ON LOWER TEE BAR MIDDLE DEVICE 1N4148 D3 75 2 R20 lt Wee t 5BY cts 1000UF 63 1N4148 D4 cs 0 01UF 100Y COMPANY CLASSE AUDIO INC TITLE DR 9 POWE LiF TE eae en alias DRAWING NO DR 9 1RO ORAWA DJR DATE FE8 20 91 SHEET 1 OF 1
8. set before relays Check relays Check capacitors on protection circuit PRO SVR_LEGACY Page 7 of 11 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 7Q resistor and 10Q 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 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 E C
9. the following tests can be performed before the unit is send to the burn in bench for a 24 hours warm up Connect the unit to a load and to a source using balanced inputs and single ended inputs independently 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 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 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 Redo steps 10 to 13 before shipping to the customer PRO SVR_LEGACY Page 5 of 11 Protection Modes and Indicators The protection circuit on the DR 9 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 the 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 that is runn
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