QSC_RMX_Series_(Rev.B)_Service_Manual 电路图.pdf

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1、Technical Service Manual RMX Series LLLLLRMX 850 LLLLLRMX 1450 LLLLLRMX 2450 *TD-000098-00* TD-000098-00 Rev. B RadioFans.CN 收音机爱 好者资料库 RadioFans.CN 收音机爱 好者资料库 RMX Series Technical Service Manual1 QSC Audio Products, Inc. Technical Services Group Phone:1-800 QSC AUDIO (1-800-772-2834) USA only +1 (7

2、14) 957-7150 Fax:+1 (714) 754-6173 Postal:1665 MacArthur Blvd. Costa Mesa, California 92626 USA E-mail:tech_ Web: (product information and support) (parts and accessory sales) RMX 850 RMX 1450 RMX 2450 RMX Series Technical Service Manual Copyright 2001, 2002 QSC Audio Products, Inc. All rights reser

3、ved. Document # TD-000098-00, Rev. B. Released February 2002. RadioFans.CN 收音机爱 好者资料库 2QSC Audio Products, Inc. RMX 850RMX 1450RMX 2450 OUTPUT POWER in watts FTC: 20 Hz20 kHz 0.1% THD, both channels driven 8 per channel185260450 4 per channel280400650 EIA: 1 kHz 0.1% THD, both channels driven 8 per

4、channel200280500 4 per channel300450750 1 kHz 1% THD, typical, both channels driven 2 per channel4307001200 Bridge Mono: 8, 20 Hz20 kHz, 0.1% THD5308001300 8, 1 kHz, 0.1% THD6009001500 4, 1 kHz, 1% THD, typical83014002400 DYNAMIC HEADROOM2 dB 4 DISTORTION SMPTE-IM 0.01% 0.01% 300 8 NOISE (unweighted

5、 20 Hz to 20 kHz, below rated output)100 dB100 dB100 dB VOLTAGE GAIN31.6 (30 dB)40 (32 dB)50 (34 dB) INPUT SENSITIVITY, V RMS full rated power 81.15v (+3.4 dBu)1.15v (+3.4 dBu)1.23v (+4.0 dBu) INPUT IMPEDANCE10 K unbalanced 20 K balanced CONTROLSFront: AC switch, Ch. 1 and Ch. 2 gain Rear: 10-positi

6、on DIP switch INDICATORSPOWER:Green LEDCLIP:Red LED, 1 per channel SIGNAL:Yellow LED, 1 per channel CONNECTORSInput:Active balanced; XLR and (6.3 mm) TRS, tip and pin 2 positive, and barrier strip Output:“Touch-Proof” binding posts and Neutrik Speakon COOLINGContinuously variable speed fan, back-to-

7、front air flow AMPLIFIER PROTECTIONFull short circuit, open circuit, thermal, ultrasonic, and RF protection Stable into reactive or mismatched loads LOAD PROTECTIONTurn-on/turn-off muting, AC coupling, triac crowbar (on each channel) OUTPUT CIRCUIT TYPEABABH AB: Class AB complementary linear output

8、H: Class AB complementary linear output with Class H 2-step high efficiency circuit DIMENSIONS19.0 (48.3 cm) wide, 3.5 (8.9 cm) tall (2 rack spaces) 15.9 (40 cm) deep (rack mounting to rear support ears) WEIGHTShipping:41 lb. (18.6 kg)46 lb. (20.9 kg)50.5 lb. (23 kg) Net:35 lb. (15.9 kg)40 lb. (18.2

9、 kg)44.5 lb. (20.2 kg) POWER REQUIREMENTSAvailable for 120 or 220240 VAC, 50/60 Hz POWER CONSUMPTION 120 VAC (both channels driven) Multiply currents by 0.5 for 230V units US patents pending SPECIFICATIONS SUBJECT TO CHANGE WITHOUT NOTICE l ac i pyT 1 l l uF 2 xaM 3 e l d IA5 . 0 8 A3A1 . 4A4 . 7 4

10、A5 . 4A6 . 6A5 . 11 2 A5 . 6*A5 . 9*A71 l ac i pyT 1 l l uF 2 xaM 3 e l d IA5 . 0 8 A7 . 3A4 . 5A01 4 A6A6 . 9A61 2 A3 . 9*A7 . 41*A52 l ac i pyT 1 l l uF 2 xaM 3 e l d IA6 . 0 8 A4A7 . 9A4 . 61 4 A3 . 6A6 . 51A72 2 A2 . 9*A32*A14 RMX Series Performance Specifications RMX Series Technical Service Ma

11、nual3 Table of Contents RMX Series Performance Specifications . 4 1. Introduction . 6 1.1 Service bulletins. 6 1.2 The well-equipped service bench . 6 1.3 Working with surface-mount components . 6 1.4 Series description . 8 1.5 Technical descriptions and theory of operation. 8 2. Component identific

12、ation and pinout . 10 3. Troubleshooting: Symptoms, causes, RMX0002, “RMX Turn-on Delay” (all RMX models); RMX0003, “RMX 2450 Turn-off Mute” (RMX 2450); RMX0004, “RMX 2450 AC Wire Routing” (RMX 2450); RMX0005, “RMX 2450 AC Wire Replacement” (RMX 2450); and RMX0006, “RMX 2450 IRFZ44N Field Effect Tra

13、nsistors (RMX 2450). 1.3 Working with surface-mount components RMX amplifiers, like many modern electronic products, use surface-mount technology (SMT) components where appropriate in order to make high-density circuitry that is reliable and economical to manufacture. SMT components in the RMX amps

14、are used in the small-signal and control circuits, so they do not handle significant amounts of power; therefore, they are subject to very little stress and should seldom fail. Sometimes they do fail, or they require replacement for a performance upgrade or modification. Thus, it is important to kno

15、w how to work with SMT components. Specialized tools and equipment exist for soldering, unsoldering, and removing SMT components quickly and efficiently, but they are often expensive. Most SMT repairs, though, can be handled reasonably well with common tools and equipment, such as tweezers, solder b

16、raid, and fine-tip soldering irons. The original factory components are tacked to the board with a spot of glue, so you might have to apply some force to break the adhesive. Two-terminal components (resistors, capacitors, diodes, etc.) Removal 1 Use two soldering irons, preferably about 25 to 40 wat

17、ts, with fine tips. 2 With a soldering iron in each hand, hold one tip on the solder at one end of the component and the other tip on the other end (Figure 1.1). 3 Once the solder melts on both ends, grip the component between the two tips and lift it from the circuit board. 4 Use solder braid and a

18、 soldering iron to remove the solder from the two pads (Figure 1.2). 1.2 The well-equipped service bench To properly service RMX amplifiers, a technician needs the right tools. The technicians service bench should have the following equipment: Digital multimeter with RMS AC voltage and current Digit

19、al clamp-on ammeter Dual-trace oscilloscope Audio distortion analyzer Non-inductive load resistors, configurable as 8 ohms (min. 500 watts capacity), as 4 ohms (min. 750 watts capacity), and 2 ohms (min. 1200 watts capacity) Variable AC voltage source, such as a Variac or Powerstat variable transfor

20、mer, with a rated current capacity of up to 25A (for 120V models) or 12A (for 230V models) Low-distortion audio sine wave generator Philips and flat screwdrivers Soldering iron with a fine tip (2560W recommended) Rosin-core solder (60/40 or 63/37) Long-nose pliers Diagonal cutters Wire strippers Aut

21、omated test equipment, such as an Audio Precision workstation, is very useful for servicing RMX amplifiers. Contact QSC Technical Services to obtain applicable AP test files. Figure 1.1. Figure 1.2. RMX Series Technical Service Manual5 Solder Solder Tweezers Solder Insertion 1 With a soldering iron

22、and 60/40 or 63/37 eutectic-type solder, melt just enough solder onto one pad to create a small mound (Figure 1.3). 2 Grasp the component in the middle with tweezers. Melt the small mound of solder with the iron and place the component across the two pads (in the correct orientation, if the componen

23、t is sensitive to direction) and press it flat against the circuit board, with one end of the component immersed in the melted solder (Figure 1.4). 3 Hold the component in place and take the soldering iron away. Let the solder harden to tack the component in place. 4 Fully solder the other end of th

24、e component to its pad. Let the solder harden (Figure 1.5). 5 Fully solder the tacked end of the component to its pad (Figure 1.6). Three-terminal components (transistors, etc.) Removal 1 With a soldering iron and solder braid, remove as much solder as possible from the middle terminal of the compon

25、ent. 2 With a soldering iron in each hand, hold one tip on the solder at the terminal at one end of the compo- nent and the other tip on the terminal at the other end. 3 When the solder on both ends melts, grip the component between the two tips and lift it from the circuit board. You might need to

26、quickly touch the pad on the middle terminal with a soldering iron to melt any remaining solder that might be holding the component down. 4 Use solder braid and a soldering iron to remove the solder from the three pads. Insertion 1 With a soldering iron and 60/40 or 63/37 eutectic-type solder, melt

27、just enough solder onto one pad to create a small mound of solder. 2 Grasp the component with tweezers. Melt the small mound of solder with the iron and place the component in the correct orientation across the three pads and press it flat against the circuit board, with one terminal of the componen

28、t pressed into the melted solder. 3 Hold the component in place and take the soldering iron away. Let the solder harden to tack the component in place. 4 Fully solder the other terminals of the component to their pads. Let the solder harden. 5 Fully solder the tacked terminal of the component to its

29、 pad. Multi-pin components (ICs, etc.) Removal Removing a multi-pin SMT component is a delicate procedure. Ideally, you should use a soldering iron with an attachment that allows you to heat all the pins simultaneously. If such a soldering device is not available, use this procedure: 1 Use a solderi

30、ng iron and solder braid to remove as much solder as possible from the pins of the component. 2 With fine tweezers, carefully try to lift each pin to see if its free. If its not, touch it with the tip of the soldering iron and if necessary, use the solder braid to remove the remaining solder. 3 Repe

31、at the process until all the pins are free and you can remove the component. Insertion 1 With a soldering iron and 60/40 or 63/37 eutectic-type solder, melt just enough solder onto one pad to create a small mound of solder. It is usually easiest to use a pad that corresponds to one of the end or cor

32、ner pins of the component. 2 Grasp the component with tweezers. Melt the small mound of solder with the iron and place the component in the correct orientation upon its pads and gently press it flat against the circuit board, with the appropriate terminal of the component pressed into the melted sol

33、der. 3 Hold the component in place and take the soldering iron away. Let the solder harden to tack the component in place. 4 Fully solder the other terminals of the component to their pads. Let the solder harden. 5 Fully solder the tacked terminal of the component to its pad. Figure 1.3. Figure 1.4.

34、 Figure 1.5. Figure 1.6. 6QSC Audio Products, Inc. 1.4 Series description QSCs RMX Series amplifiers are entry-level professional audio products, designed for good, basic performance and reliability at low price. The series comprises three models: the RMX 850, RMX 1450, and RMX 2450. Each one has tw

35、o audio channels and is two rack spaces tall. See page 2 for complete specifications. The RMX 850 and RMX 1450 have single-sided printed circuit boards. The RMX 2450 uses double-sided boards. 1.5 Technical descriptions and theory of operation Note: Some of these descriptions concern circuitry that i

36、s duplicated in the amplifiers two channels. For the sake of simplicity, the descriptions are of Channel 1 only. Components in Channel 1 have a 3-digit designation with “1” as the first digit; their equivalents in Channel 2 have a “2” as the first digit, followed by the same two numerals. For exampl

37、e, R122 and R222 have identical functions in their respective channels. Power supplies Unlike other recent QSC amplifiers, the RMX line uses strictly conventional power supplies, with large transformers that operate at the 50 or 60 Hz frequency of the AC line. The electrical current in the secondary

38、 circuitry is converted to DC through a full-wave bridge rectifier. The resulting 100 or 120 Hz ripple is filtered out by large capacitors that also serve as current reservoirs for short-term, transient demands. The supply provides a bipolar set of supply rails for each channel, with equal quiescent

39、 positive and negative voltages, as shown in Figure 1.7. Note that unlike many bipolar supplies for complementary transistor arrangements, the secondary windings are not connected to ground at the center. This is because the output transistors are directly mounted to the heat sink, metal-to-metal, t

40、o maximize heat transfer; this grounds the collectors, requiring somewhat different output and power supply arrangements. The grounded-collector concept is described later in this chapter. In the RMX 2450, the secondaries are tapped to provide an intermediate set of bipolar rails for the Class H out

41、put circuitry. Figure 1.8 shows one channel. Class H operation is described later in this chapter. The 24-volt cooling fan is driven by a separate DC supply that is powered by a +Vcc -Vcc +Vcc -Vcc Channel 1 Channel 2 +110V -110V +55V -55V Channel 1 Ch. 1 Center Tap To Channel 2 Center Tap 125W 2 0.

42、047 F 20-volt tap on the transformer primary. To minimize fan noise, the fan speed is controlled by varying its actual DC voltage in response to the amplifiers heat sink temperatures. An optocoupler isolates the fan control circuitry from the thermal sensors. Audio circuitry The audio inputs are bal

43、anced to offer a reasonably high amount of common-mode noise rejection. The input balancing is done using a single op amp (one half of an NE5532 dual op amp) arranged as a differential amplifier. The degree of common-mode rejection is dependent on a close match between the input resistors (R100 and

44、R101 in Figure 1.9) and between the feedback resistor and the shunt resistor (R105 and R106). The circuitry uses 1% precision resistors to ensure at least 40 dB of common-mode rejection. The feedback and shunt capacitors, C101 and C103, add a first-order high-frequency roll-off, down 3 dB at 88.4 kH

45、z (over two octaves above the high end of the audio spectrum). This makes the amplifier less susceptible to RF interference, high-frequency oscillations, etc. Also in this stage, the feedback loop contains one half of a 13600 dual operational transconductance amplifier (Figure 1.10). The OTA is part of the clip limiter circuitry; when the clip limiter is activated, a control voltage increases the transconductance of the OTA, which essen- tially decreases the impedance of the feedback loop and reduces the gain of the stage i