Crown_Pulse_Series_Service_Manual电路图.pdf

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1、2005 Crown Audio, Inc. PRVENIR LE CHOC LECTRIQUE NENLEVEZ PAS LES COUVERTURES. RIEN DES PARTIES UTILES LINTRIEUR. DBRANCHER LA BORNE AVANT DOUVRIR LA MODULE EN ARRIRE. TO PREVENT ELECTRIC SHOCK DO NOT REMOVE TOP OR BOTTOM COVERS. NO USER SERVICEABLE PARTS INSIDE. REFER SERVICING TO QUALIFIED SERVICE

2、 PERSONNEL. DISCONNECT POWER CORD BEFORE REMOVING REAR INPUT MODULE TO ACCESS GAIN SWITCH. CAUTIONAVIS WARNING TO REDUCE THE RISK OF ELECTRIC SHOCK, DO NOT EXPOSE THIS EQUIPMENT TO RAIN OR MOISTURE! The information furnished in this manual does not include all of the details of design, production, o

3、r variations of the equipment. Nor does it cover every possible situation which may arise during installation, operation or maintenance. If you need special assistance beyond the scope of this manual, please contact the Crown Technical Support Group. 1718 W. Mishawaka Road Elkhart IN 46517 Phone: (8

4、00) 342-6939 / (219) 294-8200 FAX: (219) 294-8301 The lightning bolt triangle is used to alert the user to the risk of electric shock. The exclamation point triangle is used to alert the user to important operating or maintenance instructions. Crown Pulse Series Service Documenation RadioFans.CN 收音机

5、爱 好者资料库 Cautions and Warnings Exclamation Mark Symbol: This symbol is used to alert the user to make special note of important operating or maintenance instructions. Lightning Bolt Symbol: This symbol is used to alert the user to the presence of dangerous voltages and the possible risk of electric s

6、hock. DANGER: The outputs of the amplifier can produce LETHAL energy levels! Be very careful when making connections. Do not attempt to change output wiring until the amplifier has been off at least 10 seconds. WARNING: This unit is capable of producing high sound pressure levels. Continued exposure

7、 to high sound pressure levels can cause permanent hearing impairment or loss. User caution is advised and ear protection is recommended when using at high levels. WARNING: Do not expose this unit to rain or moisture. WARNING: Only properly trained and qualified technicians should attempt to service

8、 this unit. There are no user serviceable parts inside. WARNING: When performing service checks with the power off, discharge the main power supplies fully before taking any measurements or touching any electrical components. A 300-ohm 10-W resistor is recommended for this. Hold the resistor with pl

9、iers, as the resistor may become extremely hot. CAUTION: Under load, with a sine wave signal at full power into both channels, the amplifier may draw in excess of 30 amperes from the AC service mains. CAUTION: When performing tests, do not connect any load to the amplifier until instructed to do so.

10、 There is no danger to the amplifier in operating without any load (open outputs). WARNING: Do not change the position of the mode switches when the amplifier is turned on. If the position of these switches is changed while the amplifier is powered, transients may damage your speakers. WARNING: Heat

11、sinks are not at ground potential. Simultaneously touching either heatsink and ground, or both heatsinks will cause electrical shock. CAUTION: Eye protection should be worn at all times when protective covers are removed and the amplifier is plugged in. CAUTION: When performing tests that require a

12、load, the load must be resistive and must be capable of handling 1000 W (per channel). CAUTION: Disconnect the power cord before installing or removing any cover or panel. CAUTION: Electrostatic discharge will destroy certain components in the amplifier. Techicians must have approved ESD protection.

13、 Proper grounding straps and test equipment are required. 2002-2005 Crown Audio, Inc RadioFans.CN 收音机爱 好者资料库 Circuit Theory, Pulse Series Introduction This section is intended to assist maintenance and service of the Pulse family of amplifiers. Component references detailed are for channel 1. Operat

14、ion of channel 2, 3, and 4 is identical except where explicitly noted. Switch mode power supply Mains power is brought in through a small, filtered IEC inlet; the purpose of this filter is to attenuate any high frequency noise produced by the SMPS, conducting back down the mains inlet. The chassis f

15、use protects the system in the event of failure or severe abuse by the user. A second, large, common mode inductor and two small Y capacitors, provide attenuation of relatively low frequency (100kHz 1MHz) noise, conducting back down the mains. An inrush limiting power resistor (R16), is used to prev

16、ent mains current inrush. The resistor is protected by a PTC thermistor (TH1) and once the SMPS is running, a relay (RLY1) closes over, shorting out the resistor and PTC and allowing normal operation. The bridge rectifier (BR2) is used with a bank of 6 1800uF/200V capacitors (C28, C29, C33, C34, C42

17、 therefore in order to start the SMPS, a boot supply is used. The boot supply comprises of R30 and R102 (10K/2W), C76 (1000uF/63) and ZD5 (47V). C76 is charged up to 47V via R102 and R30 from the 320V rail, this then powers the control electronics until SMPS operation has started and can keep itself

18、 running. It takes approximately 4 seconds to charge C67 and the SMPS cannot be switched on until this capacitor has been fully charged. The purpose of the SMPS control electronics is to provide 85kHz switching waveforms to a pair of power IGBTS (TR24 and TR32) the micro-controller turns on the cont

19、rol electronics through an opto-coupler (OPT1). When told to start by the microprocessor, all secondary supplies of the SMPS are off, and both soft start relays are open. Immediately after being told to start, the IGBTs are producing a power square wave, which is applied to the power transformer, in

20、itially through two 50R/5W resistors (R28, R142). The function of these resistors is to limit the start up current through the IGBTs. Approximately 50mS after start up, the secondary rails are present and the SMPS is powering its own control electronics, at this point the input soft start relay RLY1

21、 will close. Approximately 100mS after RLY1 closes the relay (RLY2), across R28, and R142 will close and at this point the SMPS is fully up and running. All secondary voltages are produced by rectification of the square wave from the IGBTs. The power amplifier consists of a fairly conventional Class

22、 A driver stage driving a Class AB bipolar output stage. Each stage will be dealt with individually. Input Stage Class A Driver The input signal returned from the level control is fed via DC blocking capacitor C143 and R221. DC bias current for the Class A input stage is supplied via R222, while 4n7

23、 capacitor C116 prevents any extreme high frequency input signals from reaching the power amplifier and also provides a low source impedance at high frequencies to ensure frequency stability. The first stage of the class A driver consists of TR76 and TR77 configured as a long tailed pair differentia

24、l amplifier. Emitter resistors R238 and R239 de-sensitize the performance of the input stage to parametric variations of the two input transistors. The quiescent current for the input stage is delivered by current source TR65. Diodes D51 and D52 provide a reference voltage of approximately 1.2V, whi

25、ch is applied to the base of TR65. Approximately half of this (0.6V) will then appear across R187 (220R), which then sets the current, sourced from TR65 collector at approximately 2.7mA. In the quiescent state half of this current is driven through TR76 and TR77. Hence the voltage dropped across emi

26、tter resistors R238 and R239 will be approximately equal at 75mV. RadioFans.CN 收音机爱 好者资料库 Overall voltage feedback of the amplifier is derived through R243 and R241. R242 and C20 provide local feedback around the Class A section only to define the dominant pole of the amplifier. C126 connected in se

27、ries with R241 gives 100% DC feedback to minimize any DC offset at the output. The resultant feedback signal is applied to the base of TR77. The collector currents of TR76 and TR77 are fed via D76 and D75 to R260 and R272 respectively. Hence, in the quiescent state, R260 and R272 should each exhibit

28、 a voltage drop of 1.35V or so. Under normal conditions the signals at the bases of TR76 and TR77 will be identical. However, under fault conditions, such as a DC offset at the output, the base voltages will become offset also. For example, in the event of a large DC offset of +50V at the output, a

29、positive DC voltage will appear at the feedback point and hence at the base of TR77. Although this would, in theory, be the full +50V, owing to C126 being rated at only 16V, the voltage will, in practice, be somewhat lower. However, the important issue is that the voltage is positive. In the event t

30、he voltage is negative this indicates that the feedback network is faulty (most likely R243 itself). The voltage at TR77 base being positive whilst the base of TR76 is close to 0V will then reverse bias TR77 base-emitter hence turning off the transistor. Hence, no voltage should appear across R239 a

31、nd R272 while double the normal voltage will appear across R238 and R260 (150mV and 1.3V respectively). Should this not be the case, it indicates a fault in the input stage itself. The output of the input long-tailed-pair (i.e. the voltages at the anodes of D76 and D75) are fed to a second long-tail

32、ed-pair TR80 and TR81. The bias current for this stage, is set by resistor R261 thus; D76 drops approximately the same voltage as the base-emitter junction of TR80. The same can be said of D75, and the base-emitter junction of TR80. This sets a current of about 5.75mA, split between TR80 and TR81. C

33、137 and C138 provide a little Miller Feedback around TR80 and TR81 respectively. These capacitors can be important to the stability of the amplifier but do not define the dominant pole. It should also be noted that either of these capacitors becoming leaky (difficult to measure in circuit) will resu

34、lt in a DC offset at the output. The collector of TR81 drives the output stage in conjunction with the collector of TR67 while the collector of TR80 drives current mirror TR66/TR67 via R212. In the quiescent state R212 will show a voltage drop of around 52V, and the current mirror emitter resistors

35、R188 R189 and will show equal voltage drops of 145mV. Hence, for the same +50V DC offset, described earlier, one would expect no voltage drop across any of R212, R188 or R189, indicating that the feedback is attempting to correct the fault. Likewise, for a negative DC offset one would expect these v

36、oltages to be twice their usual value. If this is not the case then the second stage (TR80-TR67) is at fault. The collectors of TR81 and TR67 are joined to form the output of the class A driver by the Vbe multiplier - R128, R127 and TR71 (mounted on the heatsink) bypassed at AC by C124 - which sets

37、the output stage bias. The bias voltage across the Vbe multiplier should range between 2.4V (heatsink warm) and 2.5V (heatsink cold). Bias voltages outside this range indicate a fault with the Vbe multiplier and/or a fault in the second long- tailed pair (TR80 - TR81, R261, R212, R188, R189). For ex

38、ample, too small a bias voltage could be caused by: R261 being high, R189 being high, R127 being low, TR71 being faulty etc. Too high a bias voltage is rare, and would, most likely, be caused by a faulty transistor or resistor in the Vbe multiplier circuit. C132 is very important for ensuring HF Sta

39、bility. A faulty capacitor in this position will usually cause excess distortion and in the case of anything less than 100pF can reveal a very spiky instability. Output Stage The output stage consists of a symmetrical Siklai follower - TR89-TR59, R189, R29A, R35A, R56A and C21A - generating the high

40、 current drive required for the parallel connected symmetrical follower output stage TR57, TR73, TR79, and TR93, R231, R244, R248, R257. V-I limiting is controlled by TR90, TR68B, R36A-R43A, C1A, C2A, R212, R25A-R27A, R30A, R33A, R55A, D7A-D9A, D11A, ZD76-ZD6A. As the output stage is symmetrical, th

41、e positive half only will be described (Q13A-Q16A, R44A- R47A, C2A, TR68A, R36A-R39A, R25A, R26A, R30A, R55A, D8A, D11A, ZD76, ZD5A). Output stage protection is accomplished by a three-slope V-I limiting circuit which has limiting characteristics chosen to emulate the Safe operating area of the outp

42、ut stage transistors at their maximum operating temperature. The V-I limiting works by controlling TR68A: when the base-emitter voltage of TR68A exceeds about 0.65V then TR68A turns on and steals current, via D8A, from the input of the output stage and thereby limiting the output. So, V-I limiting i

43、s controlled by controlling the base-emitter voltage of TR68A. Each output device has its own current sharing resistor - R44A-R47A - the voltage across which is proportional to the current flowing in the output device. These voltages are sampled and summed by R36A-R39A. C2A ensures stability when V-

44、I limiting is activated. The voltage across the output devices is sampled by R25A and R26A (R30A and ZD5A limit the voltage range to reduce off- load distortion) and this, summed with the output current derived signals from R36A-R39A, controls TR68A for output voltages less than about 3Vpk. Thus the

45、 amplifier is protected for short circuits because the base-emitter voltage of TR68A increases when output current increases and when voltage across the output devices increases. For output voltages exceeding about 3Vpk, ZD76 conducts connecting R55A to sense the output voltage. In this case, as out

46、put voltage increases, the base-emitter voltage of TR68A reduces, thus the current limit is increased as the output voltage increases, defining the third slope of the limiting characteristic. “Peak” LED circuit The “peak” LED (LED1A) is driven in series with the Limiter LED (LED2A) from the output o

47、f the amplifier via D13A with its threshold controlled by ZD7A and R58A. With no signal present, ZD7A and R58A generate a reference voltage at the anode of ZD7A, which is 18V below the +HT supply rail. All the current flowing through R58A comes from ZD7A. To turn the LEDs on, the amplifier is requir

48、ed to produce an output voltage approximately 5V above the reference, at which point ZD7A is no longer in breakdown and the current flowing through R58A comes from the output stage via D13A, LED1A and LED2A. Thus the “peak” LED threshold and the “Clip Limiter” threshold vary with the +HT voltage and

49、 thus the output loading conditions. Protection System The protection system is based around IC1, a TL074 quad op-amp. The temperature of the heatsink is monitored by TH1, an LM35DZ temperature sensor integrated circuit producing 10mV / o C. The temperature signal is then multiplied by 10 by one op-amp (pins 8,9,10) it is a tight fit), and then lift up and away from the chassis. After removing the PCB from the chassis, discharge the power supply capacitors. For C75 use a 1k/5W resistor. For the bulk reservoir capacitors, use a 10k/5W resistor. 2