AudioPro-AP3000-pwr-sm维修电路原理图.pdf
SERVICE MANUAL 3000 HIGH EFFICIENCY STEREO POWER AMPLIFIER U.S.A. Yorkville Sound Inc. 4625 Witmer Industrial Estate Niagara Falls, New York 14305 USA Voice: (716) 297-2920 Fax: (716) 297-3689 WORLD HEADQUARTERS CANADA Yorkville Sound 550 Granite Court Pickering, Ontario L1W-3Y8 CANADA Voice: (905) 837-8481 Fax: (905) 837-8746 Quality and Innovation Since 1963 Printed in Canada VERSION 1.50 October 1998 RadioFans.CN 收音机爱 好者资料库 1 AUDIOPRO AP-3000 SERVICE MANUAL M1012 “THE INPUT BOARD” The input board processes the audio signal from the input jacks to the voltage amplifier board, (M1011). Each channel consists of a balanced gain stage, defeatable bass boost filter, and a preemphasis filter network. The balanced input, (XLR Jack) and unbalanced input (phone jack) are wired in parallel to the input of a balanced operational amplifier, (U1). The gain of this stage is 1.6 (4dB) balanced and 1.6 (4dB) unbalanced. Resistors R1, R5 along with capacitors C1 and C2 form a radio interference elimination filter. Switch S1 selects a flat or bass boosted frequency response. The bass boost filter provides a 20Hz high pass, high Q filter response with a +4dB peak at 55Hz. The filter consists of a tee network on the input of U1A along with R9, R10, R11, C5 and C6. The gain is 1 (0dB) in the passband, (above 100Hz). Operational amplifier U3B is a high pass shelving filter with a +2dB shelf above 20KHz. This filter provides the pre- emphasis required to obtain a flat frequency response (to 20KHz) on the power amplifier output at full power. M1011 VOLTAGE AMPLIFIERS AND SYSTEM CONTROL This board contains: Voltage amplifiers to drive the current amplifiers on the M1002 boards. The front panel volume control circuitry. The EMS control system with its associated circuits: Pre clipping and line current sensing heater circuits. Clip and activity LEDs. Driver circuitry for the amplifier disable relay (used during amplifier turn on, turn off, thermal shutdown and current limiting). Circuit Explanation: Refer to the schematic of M1011 as the sections of the circuit are explained. The audio signal enters the board from M1012 through connector MS4. The two channels are marked L and R for left and right. The signals are to be considered as differential sources and therefore are marked as L+, L-,R+ and R-. Since the left channel has the same topology as the right channel we will only look at the left channel. The signal (L+) at the terminal block (MS4) passes through the front panel level control (P1) and the desired level enters the inverting input of U1. Op amp U1 is an inverting amplifier with a set gain of 2.40 (7.6dB). Built around U1 is a dual purpose circuit controlled by a voltage divider consisting of R15, R16, R17, R18, R19, R20 and R21. The voltage divider sets two reference levels, (HDRM & CLP). Reference voltage levels vary with the voltage levels on the +/-100VDC supply rails. As the amplifier?s output is loaded, the supply rails voltage decreases and so do the reference levels. Transistors Q1, Q3 the surrounding resistors provide a pre-clipping function that tracks the supply rails through the HDRM voltage reference and clips the audio signal at approximately 11.2V pk. The clip LED indicator circuit is connected through D1 and D2 to the output of U1, The bases of Q2 and Q4 are connected to the “CLP” reference voltage, and when the peak output voltage of U1 (+/-Vp) is enough to forward bias the transister junctions, Q2 or Q4 will trigger the clip led circuit (Q5), and eliminate the clip LED. INSTRUCTIONS PERTAINING TO A RISK OF FIRE, ELECTRIC SHOCK, OR INJURY TO PERSONS. CAUTION: TO REDUCE THE RISK OF ELECTRIC SHOCK, DO NOT REMOVE COVER (OR BACK). NO USER SERVICEABLE PARTS INSIDE. REFER SERVICING TO QUALIFIED SERVICE PERSONNEL. Read Instructions: The Owners Manual should be read and understood before operation of your unit. Please, save these instructions for future reference. Packaging: Keep the box and packaging materials, in case the unit needs to be returned for service. Warning: When using electric products, basic precautions should always be followed, including the following: Power Sources: Your unit should be connected to a power source only of the voltage specified in the owners manual or as marked on the unit. This unit has a polarized plug. Do not use with an extension cord or receptacle unless all three blades can be fully inserted to prevent blade exposure. Precautions should be taken so that the grounding scheme on the unit is not defeated. Power Cord: The AC supply cord should be routed so that it is unlikely that it will be damaged. If the AC supply cord is damaged DO NOT OPERATE THE UNIT. Service: The unit should be serviced only by qualified service personnel. INSTRUCTIONS RELATIVES AU RISQUE DE FEU, CHOC LECTRIQUE, OU BLESSURES AUX PERSONNES. AVIS: AFIN DE RDUIRE LES RISQUE DE CHOC LECTRIQUE, NENLEVEZ PAS LE COUVERT (OU LE PANNEAU ARRIRE). NE CONTIENT AUCUNE PICE RPARABLE PAR LUTILISATEUR. CONSULTEZ UN TECHNICIEN QUALIFI POUR LENTRETIENT. Veuillez lire le manuel: Il contient des informations qui devraient tres comprises avant lopration de votre appareil. Conservez S.V.P. ces instructions pour consultations ultrieures Emballage: Conservez la boite au cas ou lappareil devait tre retourner pour rparation. Warning: Attention: Lors de lutilisation de produits lectrique, assurez-vous dadhrer des prcautions de bases incluant celle qui suivent: Alimentation: Lappareil ne doit tre branch qu une source dalimentation correspondant au voltage spcifi dans le manuel ou tel quindiqu sur lappareil. Cet appareil est quip dune prise dalimentation polarise. Ne pas utiliser cet appareil avec un cordon de raccordement moins quil soit possible dinsrer compltement les trois lames. Des prcautions doivent tres prises afin deviter que le systme de mise la terre de lappareil ne soit dsengag. Cordon dalimentation: vitez dendommager le cordon dalimentation. NUTILISEZ PAS LAPPAREIL si le cordon dalimentation est endommag. Service: Consultez un technicien qualifi pour lentretien de votre appareil. IMPORTANT SAFETY INSTRUCTIONS safe_v3.doc Version 3.5 Mar 98 RadioFans.CN 收音机爱 好者资料库 2 The audio signal on the output of U1 enters U3 through R43 and RV1. Under normal operating conditions the gain of U3 is 1(0dB). The signal then passes through U2 to the voltage amplifier. VOLTAGE AMPLIFIER: The voltage amplifier amplifies the audio signal?s voltage from 6.5 volts peak (at the output of U2) to approximently 70v peak which is required to drive the current amplifier board M1002. M1002 provides the current required for the 70v peak signal to drive 1200 watts into 2 ohms out of the binding posts. Before the circuit is described in detail here is a quick rundown on the signal?s path through the voltage amplifier stage. Refer to the schematic of M1011. Lets consider that a positive going AC signal is present test point 3. The positive going signal will turn on the positive side of the voltage amplifier. The signal at test point 3 turns on Q12 (through R40, D14 and D13). The collector of Q12 pulls down on the base of Q14, turns this transistor on further and allows a greater current to flow out of Q14?s collector. This increase in current passes through Q15 and it?s collector to emitter voltage drop decreases. The collector of Q15 now being more positive in voltage turns the base of Q18 on causing an increase in Q18?scollector current resulting in test point 5 going positive. As the positive side of the amplifier was turning on the negative side would have been turning off. This is how test point 5 was able to move positive following the input signal. The reverse would hold true if a negative going signal was present on the input of the voltage amplifier. CIRCUIT DESCRIPTION: The voltage amplifier is a mirrored image with circuitry connected to the positive power supply rail being identical (but opposite polarity) to the circuitry connected to the negative power supply rail. For this reason we will look in detail at the positive side of the amplifier. The audio signal enters the voltage amplifier at test point 3. The signal passes through R40, D14 and D13 to the base of Q12. Diodes D13 and D14 set up the DC bias on Q12 to approximately 0.6 mA. The first voltage gain stage consists of Q12 along with the resistor chain on its collector and the emitter resistor (R44). Transistor Q12 drives the base of Q14 through the resistor chain. A DC current of approximately 6 mA should flow through the collector of Q14. The voltage drop across Q14 remains constant and is derived from the voltage drop across the voltage reference Q20, resistor R58, and the base/emitter junction of Q15. This total voltage should equal approximately 3 VDC. Transistor Q14 is the second gain stage and its output current flows through Q15. Transistor Q15 is a common base stage with the collector driving the base of output buffer Q18. Diode D17 is a clamping diode that prevents the maximum peak of the audio signal from coming within 4V of the 100 VDC rail. This is to prevent the output current amplifier (board M1002) from going into saturation during clipping and therefore having storage delay problems. Transistor Q18 buffers the high impedance present on the collector of Q15. The output of the buffer provides a low output impedance at test point 5 and is current limited to 38mA through the clamping action of D19, D20 and D23. The signal at TP-5 drives the current amp board M1002. DC offset on the amplifier?s output is corrected by operational amplifier U2. The DC offset forms a current through R54, R14 and is blocked by C5 giving a DC offset correction gain of -1. The activity L.E.D. function is a simple charge pump circuit with a transistor that redirects a constant current path through the activity L.E.D. 3 SHUTDOWN CIRCUIT: The last circuit on board M1011 is the shutdown relay and its associated drive circuitry. The relay circuit has two possible operating states. 1. Amplifier on under normal operating conditions. 2. Amplifier power switch has just been turned OFF/ON or the amplfier is in current limit protecting the amplifier?s output or the amplifier has overheated. CIRCUIT DESCRIPTION Here is how the circuit accomplishes these functions. The relay?s normally closed contacts short the output of the voltage amplifiers to ground when the power switch is off. When the power switch is turned on, the relay remains off (normally closed) for about 6 seconds. C52 charges to 35V and results in Q37 turning off allowing Q36 to turn on. As Q36 turns on, it connects the negative terminal of the relay?s coil (Pin 16) to ground energizing the relay and opening the normally closed contacts. If prolonged current limiting occurs on the amplifier?s output transistors then D50 or D51 (depending on which channel is current limiting) will be forward biased turning on Q38 (from its off state). Now +100VDC appears on the collector of Q38 and through R130 and R128 turn on Q37 therefore turning off Q36 by shorting its base emitter junction. Q36 turning off will turn the relay off and the normally closed contacts (off state) will short the outputs of the voltage amplifiers to ground so as not to continuously stress the amplifier?s output transistors. A cycle now occurs. With the voltage amplifiers now disabled there is no signal driving the output transistors (Q14 to Q28) on board M1002. The current limit circuit on M1002 turns off and D50 and/or D51 are not forward biased and Q38 turns off. Through Q37 and Q36 the relay is turned back on and the voltage amplifiers are now active again, driving the output transistors. If current limiting still occurs, then the same cycle will occur. If the cause of current limiting (low impedance or short on the speaker output terminals) has been removed, then the amplifier will continue to operate normally. The third operation that the relay provides is overheat shutdown. If for some reason the fan cannot keep the heatsinks in a safe operating temperature area then the fan control circuit (on board M1013) will deliver through the kill signal line a positive current to turn Q37 on and turn Q36 off to turn off the relay and disable the voltage amplifiers. When the temperature of the amplifier has been cooled down by the fan, then the kill signal will disappear and the relay circuit will turn on the relay to resume normal operation. Anytime the relay is in the protect mode (due to the abnormal states) then contact pin 8 of the relay will illuminate LD5 (the protect LED on the front panel). M1002 “CURRENT AMPLIFIER BOARD” The current amplifier board (M1002) receives a high voltage audio signal from voltage amplifier board (M1011) and provides the current drive necessary to drive speaker cabinets. The current amplifier is a two tier complimentary output driver design controlled by a complimentary mos-fet stage. CIRCUIT DESCRIPTION - REFER TO THE SIMPLIFIED SCHEMATIC #1 ON THE FOLLOWING PAGE 4 5 QUIESCENT CONDITION: This design is class A/B and therefore the output driver transistors must be forward biased to provide low crossover distortion. In most class A/B designs, a diode chain or VBE multiplier is used to control the bias voltage and provide a means of adjusting the bias. This design is different as there isnt a diode chain or VBE multiplier. For simplicity lets consider only the positive side of the current amplifier, that is all parts between the positive power supply rails and the audio signal output/input terminals. The negative side is the same as the positive, except for polarity changes. To bias Q14, greater than 0.5V is needed from base to emitter, (or for simplicity from base to amplifier output). Points A and B are at the same potential, so consider them to be connected. If this is true then 0.5V from test point 2 to the amplifier output must appear across R12. There must be some way of developing this voltage across R12, and there is using the mos-fet (Q5) driver along with local feedback. Simplified schematic Fig. #1 shows the biasing circuit. The current needed to develop 0.5V across R12 comes from the source of Q5. When the amplifier is first turned on the current source (Q3) turns on Q5 and current flows through R12 developing a voltage. When this voltage approaches 0.5V Q1 turns on and robs current from the gate of Q5. This causes Q5 to turn off until the reduced current flowing through Q5 maintains 0.5V across R12. Q1 will turn off slightly causing Q5 to increase its source current. The circuit reaches a point of equilibrium with approximately 0.5V across R12. Because all output devices are not identical and base emitter voltages vary, some adjustment must be available to slightly adjust the 0.5V across R12. This is accomplished with RT1. RT1 causes Q1 to turn on slightly more or less resulting in Q5 turning on slightly more or less and therefore R12? s voltage will be slightly more or less than 0.5v. The proper quiescent current adjustment is 4mV
