QSC-ISAseries-pwr-sm维修电路原理图.pdf

Technical Service Manual ISA Series ISA280 ISA300T ISA300Ti ISA450 ISA500T ISA500Ti ISA750 ISA800T ISA800Ti ISA1350 *TD-000163-00* TD-000163-00 Rev. A QSC Audio Products, Inc. Costa Mesa, CA 92626 USA RoHS RadioFans.CN 收音机爱 好者资料库 RadioFans.CN 收音机爱 好者资料库 Technical Service Manual1 ISA Series Power Amplifiers QSC Audio Products, Inc. Technical Services Group Phone:1-800 QSC AUDIO (1-800-772-2834) USA only +1 (714) 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) ISA280 ISA450 ISA750 ISA1350 ISA300T XLR (pin 2 +) and detachable Euro-style terminal blocks Output:Screw terminals with safety shroud DataPort V2:HD-15 female COOLINGContinuously variable speed fan, back-to-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 (2-tier)H (3-tier) AB: Class AB+B complementary linear output H: Class AB+B complementary linear output with Class H 2- or 3-tier high efficiency circuit DIMENSIONS19.0 (48.3 cm) wide, 5.25 (13.3 cm) tall (3 rack spaces) 15.9 (40 cm) deep (rack mounting to rear support ears) WEIGHTShipping:ISA 280: 42 lb (19.1 kg)ISA 450: 46 lb (20.9 kg)ISA 750: 50.5 lb (23 kg)68 lb (30.8 kg) ISA 300Ti: 50 lb (22.7 kg)ISA 500Ti: 55 lb (25 kg)ISA 800Ti: 63 lb (28.6 kg) Net:ISA 280: 35 lb (15.9 kg)ISA 450: 40 lb (18.2 kg)ISA 750: 44.5 lb (20.2 kg)77 lb (34.4 kg) ISA 300Ti: 44 lb (20 kg)ISA 500Ti: 49 lb (22.3 kg)ISA 800Ti: 57 lb (26 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 RadioFans.CN 收音机爱 好者资料库 Technical Service Manual7 ISA Series Power Amplifiers 1. Introduction 1.2 Service bulletins Contact QSC Technical Services to make sure you have the most up-to-date service bulletins for ISA Series amplifiers. Service bulletins may be distributed in hard copy, via fax, and electronically (Adobe Acrobat PDF) via CD-ROMs, FTP from the QSC web site (), and e-mail. One service bulletin has been issued for the ISA Series at the time this manual was printed: ISA0001, “ISA Turn-on Hangup” (ISA450, ISA500T, ISA750 and ISA800T) 1.1 Restriction of Hazardous Substances Directive (RoHS) Beginning in June 2006 (serial number date code 0606xxxxx), all ISA Series amplifiers are manufactured to conform to the European Unions RoHS Directive, which reduces the amount of hazardous substances allowed in products for sale within its member nations. In electronic equipment such as audio power amplifiers, this applies primarily to certain toxic heavy metals, such as lead, which may be present in electronic components, solder, and other parts. RoHS-compliant materials When servicing RoHS-compliant amplifiers, it is important for the service technician to use only RoHS-compliant components and solder (lead-free). All replacement parts provided by QSC for RoHS-compliant products are certified as RoHS compliant. RoHS-compliant tools Soldering irons and desoldering apparatus used on RoHS-compliant products must also not be contaminated by hazardous substances, such as lead. Therefore, you cannot use the same soldering and desoldering tools for RoHS-compliant products and solder as you do for non-compliant products and solder. You must either use separate soldering irons, desoldering tools and braid, etc., or at the very least designate separate tips and braids and use only the appropriate ones. If you contaminate a tip or braid, even inadvertently, by using it on a non-compliant product or solder, you can no longer use it with RoHS-compliant products or solder. 1.3 The well-equipped service bench To properly service ISA amplifiers, a technician needs the right tools. The technicians service bench should have the following equipment: Digital multimeter with RMS AC voltage and current Digital 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 transformer, 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 (RoHS-compliant solder, or 60/40 or 63/37 for non-RoHS product only) Long-nose pliers Diagonal cutters Wire strippers Automated test equipment, such as an Audio Precision workstation, is very useful for servicing ISA amplifiers. Contact QSC Technical Services to obtain applicable AP test files. RadioFans.CN 收音机爱 好者资料库 8QSC Audio Products, Inc. TD-000163-00 Rev. A Solder braid Solder Solder Tweezers Solder 1.4 Working with surface-mount components ISA 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 ISA amps 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 know 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 braid, 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 watts, 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 soldering iron to remove the solder from the two pads (Figure 1.2). Insertion 1 With a soldering iron and appropriate 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 component 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 the 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 component. 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 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 appropriate solder, melt 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 component 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 pad. Figure 1.1. Figure 1.2. Figure 1.3. Figure 1.4. Figure 1.5. Figure 1.6. RadioFans.CN 收音机爱 好者资料库 Technical Service Manual9 ISA Series Power Amplifiers 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 soldering 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 Repeat the process until all the pins are free and you can remove the component. Insertion 1 With a soldering iron and appropriate 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 corner 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 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 pad. RadioFans.CN 收音机爱 好者资料库 10QSC Audio Products, Inc. TD-000163-00 Rev. A 1.5 Series description QSCs ISA Series amplifiers are entry-level professional audio products for installed sound systems, designed for good, basic performance and reliability at low price. The series comprises seven current modelsthe ISA280, ISA300Ti, ISA450, ISA500Ti, ISA750, ISA800Ti, and ISA1350and three discontinued ones the ISA300T, ISA500T, and ISA800T. Outputs for distributed lines While all ISA models can drive low-impedance speaker loads as low as 2 ohms per channel, the three ending in “Ti” also have isolated transformer-coupled outputs for driving 25-, 70-, or 100- volt lines. The “T” models preceded the “Ti” ones and had non- isolated autoformer-coupled outputs; other than this distinction, they are the same as the “Ti” models. Note: For the sake of brevity, information that pertains to both versions will be combined in descriptions of the “Ti” models, except where otherwise noted. Each model has two audio channels and is three rack spaces tall. See page 2 for complete specifications. The ISA280, ISA300Ti, ISA450, and ISA500Ti have single-sided printed circuit boards. The ISA750, ISA800Ti, and ISA1350 use double-sided boards. 1.6 Technical descriptions and theory of operation Note: Some of these descriptions concern circuitry that is 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 example, R122 and R222 have identical functions in their respective channels. Power supplies Unlike other recent QSC amplifiers, the ISA 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 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 positive and negative voltages, as shown in Figure 1.7. Note that unlike many bipolar supplies for complemen- tary transistor arrangements, the secondary windings are not connected to ground at the center. +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 0.047 F This is because the output transistors are directly mounted to the heat sink, metal-to-metal, to maximize heat transfer; this grounds the collectors, requiring somewhat different output and power supply arrange- ments. The grounded- collector concept is described later in this chapter. In the ISA 750 and ISA 800T, the secondaries are tapped to provide an intermediate set of bipolar rails for the Class H output 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 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 balanced 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 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 kHz (over two 10K LINEAR 3B RIGHT ANGLE POT R106 10.0K R_0805 R101 10.0K R_0805 R100 10.0K R_0805 R105 10.0K R_0805 CWCCW W R112 10K A1 R102 1K R_0805 +IN_A -IN_A C101 180p-5% C_0805 C103 180p-5% C106 10-50NP 3 + 2 - 1 NE5532 U101:1 A1 R113 270 R_0805 To LM13600 operational transconductance amp Figure 1.7 Figure 1.8 Figure 1.9 RadioFans.CN 收音机爱 好者资料库 Technical Service Manual11 ISA Series Power Amplifiers 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 h