QSC-DCA3022-pwr-sm 维修电路原理图.pdf

Product Model: DCA 1222, DCA 1622, DCA 2422, DCA 3022, DCA 3422Document #: TD-000495-00Initial Release: April 2015Revised Release: Revision: AService ManualQSC Audio Products, LLC Costa Mesa, California, USA DCA 2 Channel SeriesRadioFans.CN 收音机爱 好者资料库2QSC Audio Products, LLCRadioFans.CN 收音机爱 好者资料库3TD-000495-00 DCA 2 Channel Series Service ManualTable of Contents1. Introduction .51.1 Restriction of Hazardous Substances Directive (RoHS) .51.2 Revision history .51.3 Service bulletins .51.4 Serial Numbers .51.5 The well-equipped service bench .62. Product specification and images .73. Operational description .83.1 Series description .83.2 Circuit descriptions .84. Testing .194.1 Requirements .194.2 Setup .194.3 Test procedures .205. Troubleshooting guide.235.1 General tips and tricks.235.2 Intermittent signal from gain pots .265.3 Main PSU damage (IGBTs or flyback diodes blown) .265.4 Shorted output transistors in amplifier section .275.5 Step circuit failure .275.6 Leaky transistors in amplifier current limit circuit .285.7 Weak capacitor C107 in PSU .295.8 Input stage damage .295.9 Protect signal transistors shorted .305.10 Zobel resistors burned .306. Service updates .317. Schematics .328. Assembly drawings .338.1 DCA 2-CH chassis assembly .338.2 DCA 2-CH PCB assembly .369. Replacement parts .379.1 Amplifier module replacement summary .379.2 SG-000060-00, PLC power supply restoration kit .379.3 SG-000568-TS, PLC housekeeping (bias) rebuild kit .379.4 Finished Good (all DCA 2-channel models) .389.5 WP-000080-00, ship kit DCA 2CH .389.6 Chassis assembly, (all DCA 2-channel models) .389.7 WP-001223-00, DCA 1222 PCB assembly .409.8 WP-001623-00, DCA 1622 PCB assembly .459.9 WP-002423-00, DCA 2422 PCB assembly .509.10 WP-003023-00, DCA 3022 PCB assembly .559.11 WP-003423-00, DCA 3422 PCB assembly .604QSC Audio Products, LLCQSC Audio Products, LLC Technical Services Group 1665 MacArthur Blvd. Costa Mesa CA 92626 USADCA 2 Channel Series Amplifiers Service ManualCopyright 2014 by QSC Audio Products, LLC. All Rights Reserved. QSC and the QSC logo are trademarks of QSC Audio Products, LLC in the U.S. Patent and Trademark Office and other coun-tries. Patents may apply or be pending. Windows is a registered trademark of Microsoft Corp. Audio Precision is a registered trademark of Audio Precision, Inc. All other trademarks are property of their respective owners.+1 (714) 957-7150 1-800 QSC AUDIO (USA only) +1 (714) 754-6173 (fax) (main web site) (Technical Service Group web site) (parts and accessories sales)5TD-000495-00 DCA 2 Channel Series Service Manual1. Introduction1.1 Restriction of Hazardous Substances Directive (RoHS) QSC DCA series amplifier products 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 processors, this applies primarily to certain toxic heavy metals, such as lead, which may be present in electronic components, solder, and other parts.RoHS-compliant materialsWhen servicing RoHS-compliant electronic products, 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 toolsSoldering 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 contami-nate a tip or braid, even inadvertently, by using it on a non-compliant product or solder, you should no longer use it with RoHS-compliant products or solder.1.2 Revision historyNo revision history yet.1.3 Service bulletinsAt the publish date of this service manual, 5 service bulletins concerning the DCA series amplifiers have been issued. Check or contact QSC Technical Services Group (TSG) for the latest information on applicable service docu-ments. For a quick summary, refer to “6. Service updates” on page 31. 1.4 Serial NumbersSerial numbers on QSC DCA series amplifiers are nine digits long. The first four digits are a manufacturing date code in mmyy format; the last five digits are the sequential identifying number for each individual product. For example, a serial number of 0711xxxxx would indicate that the QSC product was manufactured in 07/2011, or July 2011. The amplifiers serial number can be found on the rear panel near the AC inlet.AMPLIFIER120 V 2.3 A 50/60HZMonthYear6QSC Audio Products, LLC1.5 The well-equipped service benchService bench setup Desoldering equipment or desoldering braid Bank of non-inductive load resistors, configurable as 8 ohms min. 1500 watts capacity), as 4 ohms (min. 3000 watts), and 2 ohms Digital multi meter with RMS AC voltage and current Digital clamp-on ammeter Dual-trace oscilloscope, 1Mhz or greater Low-distortion audio sine wave generator Audio distortion analyzer (recommended Audio Precision) Variable AC voltage source, such as a Variac or PowerstatTools required Phillips and flat head screwdriver (electric recommended) Soldering iron and solder suitable for electronics Desoldering equipment or desoldering braid Hex nut driver set, 1/2” and 7/16” Desoldering equipment or desoldering braid Basic tools for electronic repair including various pliers, wire-cutters, strippers, and crimpers.7TD-000495-00 DCA 2 Channel Series Service Manual2. Product specification and imagesDCA1222 | DCA1622 | DCA2422 | DCA3022 | DCA3422 Details1675 MacArthur Boulevard Costa Mesa, CA 92626 Ph: 800/854-4079 or 714/957-7100 Fax: 714/754-6174 DCA1222 | DCA1622 | DCA2422 | DCA3022 | DCA3422 Spec Sheet 02/06/2013please recycle 2013 QSC Audio Products, LLC. All rights reserved. QSC and the QSC logo are registered trademarks of QSC Audio Products, LLC in the U.S. Patent and Trademark office and other countries. Speakon is a registered trademark of Neutrik. DCA1222 DCA1622 DCA2422 DCA3022 DCA3422Stereo Mode (both channels driven) Continuous average output power per channel 8 / 20 Hz 20 kHz / 0.03% THD 200 W 300 W 425 W 550 W 700 W 8 / 1 kHz / 1% THD 215 W 350 W 475 W 625 W 800 W 4 / 20 Hz 20 kHz / 0.05% THD 325 W 500 W 700 W 900 W 1100 W 4 / 1 kHz / 1% THD 375 W 600 W 825 W 1050 W 1250 W 2 / 1 kHz / 1% THD 600 W 800 W 1200 W 1500 W 1700 WBridge-Mono Mode Continuous average output power 16 / FTC 20 Hz 20 kHz / 0.1% THD 400 W 600 W 850 W 1100 W 1400 W 8 / FTC 20 Hz 20 kHz / 0.1% THD 700 W1100 W 1500 W 2000 W 2300 W 4 / EIA 1 kHz / 1% THD 1200 W 1600 W 2400 W 3000 W 3400 WSignal to Noise (20 Hz 20 kHz) -106 dB -107 dB -108 dB -107 dB -107 dBInput Sensitivity at 8 1.0 Vrms 1.2 Vrms 1.5 Vrms 1.7 Vrms 1.9 VrmsInput Sensitivity at 4 0.9 Vrms 1.1 Vrms 1.3 Vrms 1.5 Vrms 1.7 VrmsOutput Circuitry Class AB Class AB 2-tier Class H 2-tier Class H 2-tier Class HPower Requirements (1/8 pink noise at 4) 6 A* 10 A* 8 A* 12 A* 12 A*Distortion (SMPTE-IM) 0.01% 0.01% 0.02% 0.02% 0.02%Distortion (typical) 20 Hz 20 kHz: 10 dB below rated power 0.01% THD / 4 and 8 1.0 kHz and below: full rated power 500Input Impedance 10k ohms unbalanced, 20k ohms balancedInput Clipping 10 Vrms (+22 dBu)Cooling Variable-speed fan, rear-to-front air flowConnectors (each channel) Input: 1/4 TRS, 3-pin XLR and 3-pin detachable terminal blocks (one per channel) Output: Neutrik Speakon and safety shrouded barrier strip, including monitor ouputControls Front: AC switch, Ch. 1 & 2 gain knobs Rear: DIP switches for Ch. 1 & 2 | clip limiter on/off | LF filter on/off | LF filter freq select -30 or 50 Hz inputs parallel or stereo; bridge modeIndicators Power-On: Green LED | Parallel inputs: Yellow LED | Bridged: Yellow LED Clip/Prot: Red LED | Level -10 dB: Green LED | Level -20 dB: Green LED | Signal -35 dB: Green LED (1 per channel)Amplifier Protection Full short circuit, open circuit, thermal, ultrasonic, and RF protection. Stable into reactive or mismatched loadsLoad Protection On/off muting, individual channel DC fault blockingDimensions (HWD) 3.5 (8.9 cm) 2 RU x 19 (48.3 cm) rack mounting x 14 (35.6 cm) from front mounting railsVoltage Gain 40 x (32 dB)Weight - Net / Shipping 21 lb (9.5 kg) / 27 lb (12.3 kg)Optional Accessories DCM Digital Cinema Monitors provide complete crossover and monitor functions Basis and QSC for a complete networked audio solution, including DSP and control and monitoring of amplifiers and loudspeakers The XC-3 cinema crossover is for bi-amp applications with all commonly used cinema speakers The SF-3 subwoofer filter is an adjustable highpass filter for subwoofers The LF-3 low frequency filter is used with the XC-3 for tri-amp applications The DSP-3 and DSP-4 digital signal processors feature a fully programmable signal chain and includes crossover filters plus numerous additional dynamics processors* at 120 VAC, both channels driven; multiply current by 0.5 for 230V units8QSC Audio Products, LLC3. Operational description3.1 Series descriptionCrystal-clear, seat-shaking cinema sound is here with our DCA Series Digital Cinema Amplifiers. Five 21 lb (9.5kg), two rack space models offer power points from 200 to 1700 watts per channel. With QSCs exclusive PowerLight switching technol-ogy youll hear ultra powerful bass and superior highs in every action scene. In addition to their superior performance, weve packed these amplifiers with useful features and every input/output connector youll ever need.3.2 Circuit descriptions3.2.1 Startup sequenceOrderly start-up and shutdown are critical to reliable operation of the switching supply. The general start-up sequence is as follows:1. Apply AC power (turn on the AC switch).2. Current flows through the inrush limiting resistor R324, charging the main filter capacitors C132, 136, 140 and C133, 137, 141.3. After about 0.5 seconds, the Bias Supply U16 starts up, supplying regulated 16V and 18V power to the switching controllers. This supplies a modest current to the Power LED via R232 (Sheet 4), causing a “half bright” condition. Power is supplied to all controller circuitry including the switching oscillator U14:1.4. Meanwhile, timer U14:2 holds the shutdown line HI for 3 seconds, allowing time for the main filters to fully charge before enabling the main supply.5. When U14:2 times out, the relay is clicked on, bypassing the inrush resistor, and the main supply begins switching. 6. The secondary capacitors are charged, the fan starts, full current is supplied to the Pilot LED via R252, and the amplifier enters a 1-second muting interval before being released to run.3.2.2 EMI filterThe EMI filter reduces both common mode and differential mode interference generated by the switching supply (and also protects against incoming spikes). All sources of in-terference have been reduced as much as possible, but a certain residue must be filtered. We attenuate the high frequency interference by increasing the series impedance (using inductance) and then shunt the high frequencies to ground (via capac-itance). Since we can only apply a small amount of capacitance from AC line to ground, to avoid coupling AC current to ground, we need as much inductance as possible.The entire EMI filter is contained in a shielded box, represented by dashed lines. This prevents capac-itive coupling of internal interference into the AC cord. It is also necessary for the AC cord wires to go directly to their terminals without resting on the coil, to avoid partial capacitive bypassing of the filter.9TD-000495-00 DCA 2 Channel Series Service Manual3.2.3 Inrush limitingPCB traces pass under the EMI shield and connect the AC voltage to wires. The high-side wire (EH1 to EH2) goes to the front corner of the PCB, to R324 and K1. R324 is a 10-ohm NTC with a large energy absorption capability (180 joules). When AC voltage is first applied, this resistor slows down the inrush of current charging the main filter capacitors. After three seconds, relay K1 clicks on and bypasses R324 for full power. Relay K1 is controlled by Q92 and Q93. For the relay to operate, the 18V supply to the coil must be active, and the 5V control line connected to R329 must go low. This turns off Q93 and enables R327 to turn on Q92. Although the relay has a 24V coil, it has a “must operate” rating of less than 18V. If the relay does not operate, the non-bypassed NTC will still support a moderate amount of amplifier power, but heavy loads will overheat it. If the NTC runs hot during regular use, the relay is not working. The AC current then goes to the main power switch (ES1 to switch), and returns via another wire (switch to ES2) which feeds one side of the AC rectifier.3.2.4 Main power supplyThe high side of the main DC filter bank is labeled PRI_HI and is about 330V above the negative rail, PRI_LO. All switching control circuitry uses PRI_LO as its local “ground”. All primary control voltages are specified with respect to PRI_LO. HOWEVER, always remember that this common reference is still connected to the AC line, and can NOT be used to ground ordinary non-isolated scope probes.An independent “bias” supply also operates from the main rails, supply-ing regulated +16V and +18V with respect to PRI_LO, plus an isolated secondary control voltage.Switching devices and high frequency power conversionThe essential principle of the PLC platform power supply is that two high frequency switching transistors, IGBT devices Q96 and Q97, switch back and forth between Pri-Hi and Pri-Lo, generating an AC square-wave voltage at about 110kHz. This couples power from the main DC reservoir to the isolated, secondary DC supply, through a high frequency transformer T2, which is much smaller than the normal 50/60-Hz AC transformer. Because of the high frequency, the core is small, all wind-ings are short and have very low losses, therefore the power transfer is improved.The Insulated Gate Bipolar Transistor can be thought of as a moderate sized FET driving a high current bipolar transistor in a Darlington configuration. The IGBT has the advantages of reduced gate drive capacitance (lower drive currents), and much lower conduction losses at high currents than the same-size FET. Its drawbacks are somewhat slow turn-off, and thus increased losses if turned off with a high current flowing.IGBTs operate best with a full 15V gate drive. When fully enhanced, peak currents of over 100A can be handled. The Pow-erlight gate drive circuit does not supply a full 15V, especially under heavy overloads, which probably limits its peak power handling. Power supply cutback values had to be set accordingly. Because of the regulated Bias supply, the PLC platform can handle plenty of power with no apparent strain. The PLX gate