6.1 Semiconductor package descriptions and pinouts ..............................89 6.2 PL325 parts and assemblies ..................................... 93 PL325 Power Amplifier (120V) (QSC part # FG-032500-00) ..................................93 PL325 Power Amplifier (100V) (QSC part # FG-032500-01) ..................................93 PL325 Power Amplifier (230V) (QSC part # FG-032500-02) ..................................93 Chassis Assembly PL325 (120V) (QSC part # WP-032500-00) ..................................
Chassis Assembly PL380 (100V) (QSC part # WP-038000-01) ..................................121 Chassis Assembly PL380 (230V) (QSC part # WP-038000-02) ..................................122 PCB Assembly PL380 (120V) (QSC part # WP-038001-00) through January 2008 ............................. 122 PCB Assembly PL380 (100V) (QSC part # WP-038001-01) through January 2008 ............................. 126 PCB Assembly PL380 (230V) (QSC part # WP-038001-02) through January 2008 .............................
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Tables and Figures (continued) Table 3.4. Troubleshooting short circuit cutback clamping ........................... 47 Figure 3.13. Output signal and positive rail steps..............................48 Figure 3.14. Output signal and negative rail steps............................... 48 PL325 and PL340 main circuit board, with major circuit sections shown ......................53 PL325 and PL340 main circuit board, top layer ..............................
Agency Approvals UL, CE, RoHS / WEEE compliant, FCC Class B (conducted and radiated emissions) * Burst mode testing required due to AC service current limitations ** Representative of current draw with tyical music program material with occasional clipping All specifications are subject to change without notice. QSC Audio Products, LLC...
1.2 Service bulletins and updates Contact QSC Technical Services to make sure you have the most up-to-date service bulletins, schematics, and parts lists for PowerLight 3 Series amplifiers. Service materials may be distributed in hard copy, via fax, and electronically (Adobe Acrobat PDF) via CD-ROMs, FTP from the QSC web site (www.qscaudio.com), and e-mail.
Figure 1.2. Use two irons • Wire strippers • PL380 Automated test equipment, such as an Audio Precision workstation, is very useful for servicing QSC amplifiers. Contact QSC Technical Services to obtain applicable AP test files. Solder braid 1.4 Working with surface-mount components PowerLight 3 amplifiers, like many modern electronic products, use surface-mount technology (SMT) compo- Figure 1.3.
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1.4 Working with surface-mount components (continued) 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 component and the other tip on the terminal at the other end.
With its class D output section, the PL380 amplifier differs from all abnormal situations such as defective op amps or other circuitry previous QSC stand-alone models, which up to now have used that could cause abnormally high or low current demand.
1.5 PL380 Service Fixture (continued) Turn off the service fixture’s power switch and connect it to the Initial tests with the service fixture AC mains. The service fixture has a universal power supply that can operate on any AC voltage from 100 to 240 volts. These initial tests with the service fixture will allow you to deter- mine whether the amplifier’s clock and control circuitry are working properly, with no risk of damaging high-power devices or circuits.
1.5 PL380 Service Fixture (continued) terminal). The voltage is derived from other low-voltage power supplies, so its presence indicates that the other supplies are probably good. If the voltage is not present, then check the other supplies and associated circuitry to find the fault. For more detailed troubleshooting, see Troubleshooting Serious Failures in Section 3.1.
DC rails of approximately ±16 V. Each of the two amplifier channels uses two large switching FETs operating as a half-bridge at a clock frequency of 250 kHz. The FETs The housekeeping flyback supply operates independently of the QSC Audio Products, LLC...
The PL380 uses the same type of HD-15 connector used on other the positive rail, and turning on the low-side switch for longer QSC DataPort amplifiers to connect to QSControl devices such as intervals will lower the output voltage towards the negative rail.
L5, L6, C226, and C227 to filter out 3. When the capacitor charges to greater than 3.3 V, the compara- switching noise. All circuitry connected to these rails will be QSC Audio Products, LLC...
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2.2 PL380 Major Circuit Blocks (continued) tor U24:1 will swing low, turning on Q35 and Q37. These actuate an actual difference to be noted. relay K2 (schematic: sheet Supply, PL380 , zone C-6), which couples AC through large NTC resistors R262 and R266 to the High Current Switching main AC rectifier BR1.
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10 V. Higher temperatures described next. will further increase the fan voltage. The maximum fan voltage available, which would be at temperatures at or about the point of QSC Audio Products, LLC...
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2.2 PL380 Major Circuit Blocks (continued) thermal shutdown, is about 30 V DC. Feedback elements R160, connects CL-A-ON to ground; when set to “enable” the clip limiter, it R157, Q45, and R153 provide stabilizing feedback to regulate the is open and allows the falling voltage at CLIP-A to let Q72 turn on fan voltage.
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LEDs. “DataPort” Connector and Monitoring Signals The DataPort is a QSC-specific connector scheme that passes low- voltage (line level) signals to and from external monitoring devices such as the Basis series. The DataPort may also host a plug-in accessory that receives power from the +15 V line and sends processed signals to the amplifier.
2.3 PL380 Test Procedure mately 2800 watts with a continuous sine wave signal). Test Equipment required: The circuit design of the PL380 is fine-tuned and requires no internal • Distortion analyzer with built-in signal generator trim pots. Therefore, no adjustment or calibration is required during The generator must have total harmonic distortion plus noise testing.
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1. Connect a 4-ohm load resistance to channel 1’s output. Apply a and -10 dB) should be lit. Set the analyzer’s 0 dB reference to 2.7 V rms, 1 kHz sine wave signal to amp channel 1’s XLR input . this level. QSC Audio Products, LLC...
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2.3 PL380 Test Procedure (continued) 2. Adjust the gain control to obtain 2500 watts output power 3. Measure AC line current; should be about 13–21 A (120 V model) (100 V rms). Verify that the THD is below 1%. Check the output or 6.5–12 A (230 V model).
3 with the other channel. 6. Turn on the analyzer’s 80 kHz filter. 7. Plug the amplifier’s power cord into a variable autoformer (set to 0 V) and set up an ammeter to monitor AC line current. QSC Audio Products, LLC...
2.4 PL340 Test and Calibration Procedure (continued) Signal Indicators Test 1. Disconnect the load resistors. 2. With a 1.96 V rms, 1 kHz input signal into the channel, turn the gain control to maximum. The three signal LEDs (Signal, -20 dB, and -10 dB) should be be lit.
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Reassemble the amplifier and verify its operation prior to returning 2. Apply a short across the output of each channel and turn the the product to service. amplifier gain controls to maximum. Clip LEDs should be on. QSC Audio Products, LLC...
2.5 PL325 Test and Calibration Procedure Test Equipment required: Power On and Mute Delay Test • Distortion analyzer with built-in signal generator 1. Turn the amplifier on and slowly increase the AC voltage to 50 V The generator must have total harmonic distortion plus noise (120 V model) or 100 V (230 V model) while monitoring the AC (THD+N) of no higher than 0.01%, and the analyzer must be line current.
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4. Adjust the bias trimpot VR43 (channel 1) or VR166 (channel 2) for a total THD+N figure of 0.07% or slightly less. Figure 2.4 shows what the residual crossover spike should look like when the bias QSC Audio Products, LLC...
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2.5 PL325 Test and Calibration Procedure (continued) 2. Turn the amplifier gain controls to maximum. Set the analyzer’s 2 Ohm Power and Short Circuit 0 dB reference to this level. Current Test 3. Disconnect the input signal from the amplifier input and measure the residual noise level produced into the load.
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This page is blank. QSC Audio Products, LLC...
3. Troubleshooting 3.1 PL380: Symptoms, causes, and remedies Relay Circuit, Inrush System. Prerequisites to troubleshooting • To prevent high surge currents that would otherwise flow into the large primary- and secondary-side capacitors, the power Safely turning on an unknown PL380 amplifier supply IGBTs start switching before voltage is applied to the main reservoir capacitors.
2. Failed switch-mode power supply: If you suspect that the What to look for switching supply IGBTs Q68 and Q69 (QSC part # QD-000315-00) are Symptoms may include one or more of these: damaged: • The amplifier draws excessive current; it may trip circuit breakers •...
Failed output FETs: If you suspect that the output switching FETs CAUTION: Voltage—even residual amounts—on the main supply Q10 and Q11 (channel 1; QSC part # QD-000318-00) or Q58 and Q59 rails can cause high current surges into a grounded scope probe (channel 2;...
• Components C15, R26, and R21 create a short pulse buffered by supplying power, the drive signal at the gates (referenced to the U5:1, which serves as the power supply sync signal. Note that it source) on each channel should be two similar but complementary QSC Audio Products, LLC...
3.1 PL380: Symptoms, causes, and remedies (continued) 0–12 V square waves, with a slightly rounded leading edge and • With your oscilloscope, check and confirm the optocoupler input steeper falling edge (see Figure 3.2). signals, with respect to ground. On channel 1, optocouplers U12 and U13 should receive a 5 V If there is any signal into the modulator, you should also observe PWM logic signal at their inputs (pin 2) .
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D47, and C139). If the rear section of the heatsink is warmer Symptoms may include one or more of these: than the front, check channel 1’s dead time circuit (R43, D4, and C29; R44, D5, and C30). • The amplifier operates, but poorly or incorrectly. QSC Audio Products, LLC...
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3.1 PL380: Symptoms, causes, and remedies (continued) Excessive distortion: Each channel should exhibit midband With no load, the output may show one or two cycles of damped (approx. 1 kHz) THD of 0.01–0.02% at output levels between about ringing after the square wave leading edge. If you increase the 50 W and 500 W (about 20–63 V rms) into 8 ohms, increasing to signal or the channel gain to nearly the point of clipping, the about 0.2% just below clipping and above about 5 kHz.
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(about 80 A peak; less current at higher FET temperatures). • Any missing or open components will prevent current clamping, which will probably allow FET failure if the outputs are shorted. QSC Audio Products, LLC...
3.2 PL325 and PL340: Symptoms, causes, and remedies When first checking the operation of an amplifier on the bench, • Perform a quick test of the bias supply as instructed in Trouble- always turn your variable autoformer down to zero before plugging shooting the TOP-210 Bias Supply Faults .
• Check the step FETs. If any is shorted, it will cause the amplifier Troubleshooting and Replacing Blown Output Transistors. to run inefficiently. See Troubleshooting Step Problems for in- depth troubleshooting. • Check for leaking capacitors C179, C180, C189, or C190. QSC Audio Products, LLC...
3.2 PL325 and PL340: Symptoms, causes, and remedies (continued) • The bias may be set excessively high. Calibrate the bias on the Faults With Signal Present suspect channel as described in the test procedure. Figure 3.10 shows an acceptable crossover spike at the distortion analyzer The customer complains that the amplifier passes a signal but output.
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• Resistor R349 subtracts about 0.5 V, bringing the net voltage at The amplifier’s IGBTs are driven by an active, direct coupled pin 4 (feedback reference) of U16 to about 5.1V. integrated circuit rather than a gate drive transformer. IGBT or driver QSC Audio Products, LLC...
PL325 • U13 has fairly high supply voltage ratings and should rarely fail. amplifier. Audio Output: Troubleshooting and replacing PLC Series Power Supply Restoration Kit (QSC damaged output transistors part number: SG-000060-00) Part Number Description Reference Qty.
R51, R72 R53, R75 R174, R195 R176, R198 If voltage is approx. 0.7 V check for missing resistor: R182 R185 If voltage is wrong check for wrong value R59, R60 R61, R62 R182, R183 R184, R185 QSC Audio Products, LLC...
3 seconds at full power. Table 3.3. Troubleshooting clamp transistors Channel and polarity ☛ Channel 1 + Channel 1 - Channel 2 + Channel 2 - Clamping voltage Measure voltage on decreases, but no Check clamp transistor current cutback QSC Audio Products, LLC...
Fault: Clip limiting doesn’t work (only one channel) With your oscilloscope, probe the op-amp output on pin 7 of U2 Figure 3.14. Output signal and negative rail steps. (channel 1) or U7 (channel 2), while the channel is clipping. If the QSC Audio Products, LLC...
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3.2 PL325 and PL340: Symptoms, causes, and remedies (continued) • Q7 (channel 1) or Q52 (channel 2), may be missing or open. Fault: FET does not stay fully turned on This generally causes clipping and possible distortion problems at • R28 (channel 1) or Q151 (channel 2), may be missing or open. low frequencies when the amp drives 2-ohm loads.
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• POSREF should be about 20 V below the +MID-RAIL node. ing specific FET types. If these problems appear in any QSC amplifier, please report it to QSC Technical Services.
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3.2 PL325 and PL340: Symptoms, causes, and remedies (continued) Audio Power Stage and Power Supply: Fault: Shutdown occurs when output signal exceeds Troubleshooting DC Fault Shutdown • Check Q87, C7, R240, and D48 for open or missing components. Normal circuit behavior •...
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29 V when hot. • If the fan voltage is okay, replace the fan. • No voltage: check Q89–Q91, R264, and 265 for open or missing components. Confirm that ±15 V supply voltages are present. QSC Audio Products, LLC...
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Ch. 1 negative Ch. 1 positive Ch. 2 positive Ch. 2 negative IGBT switches driver and driver and driver and driver and “Keep-alive” and spike EMI line output output output output supply filter filter Top side Top side Mute and fan control Output Zobel filters...
Bottom layer (mirror image) Silk screen shown for reference Bottom side (mirror image) Silk screen layer is shown for reference. PL325 and PL340 main circuit board, bottom layer, mirror image PL3 Series Service Manual TD-000274-00 Rev. A...
Bottom layer (mirror image) Silk screen shown for reference Bottom side (mirror image) Silk screen layer is shown for reference. PL325 and PL340 input board, bottom layer, mirror image PL3 Series Service Manual TD-000274-00 Rev. A...
6. Replacement parts 6.1 Semiconductor package descriptions and pinouts Legend: A = anode; B = base; C = collector; D = drain; G = gate; K = cathode; S = source IC-000024-00 IC-000047-30 PWM controller, SG3525AN COMPARATOR, DUAL, LM393, SMT OUTPUT A INV.
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INVERTING INPUT B V OUT V IN OUTPUT A OUTPUT B BUFFER INPUT A BUFFER INPUT B BUFFER OUTPUT A BUFFER OUTPUT B IC-000106-30 QD-000315-00 D FLIP FLOP, DUAL, 74HC74, SMT 600V 75A IGBT, 250W, IXGR60N60C2, TO-247 QSC Audio Products, LLC...
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6.1 Semiconductor package descriptions and pinouts (continued) IC-000316-00 IC-000342-00 Counter, 14 stage, 74HC4060, SMT TOP SWITCH, TOP244YN Y Package (TO-220-7C) Tab Internally Connected to SOURCE Pin QD-000318-00 IC-000371-30 N-channel MOSFET 500V 85A, IXFN80N50Q2, SOT-227B package MOSFET DRIVER, UCC37321D, SMT PL3 Series Service Manual TD-000274-00 Rev.
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PCB Assembly PL380 (120V) (QSC part # WP-038001-00) from February 2008– Revision notes: This revision results in the following changes in performance or operation. • The amplifier no longer goes into standby when the Basis unit shuts off. • The clip LED indicators no longer stay lit when the amplifier is in standby.
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PCB Assembly PL380 (120V) from February 2008–, continued QSC Part # Description Qty. Reference Comments CO-000106-00 JACK, HD15, 15 POS, FEMALE, RIGHT ANGLE SWAGED JACK SCREW CO-000148-00 XLR, NEUTRIK, 3 POS, FEMALE, VERTICAL J3, J4 CO-000155-00 HEADER, 0.1" CENTERS, 2 POS (1X2), MALE, RAMP LOCK...
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PCB Assembly PL380 (100V) (QSC part # WP-038001-01) from February 2008– Revision notes: This revision results in the following changes in performance or operation. • The amplifier no longer goes into standby when the Basis unit shuts off. • The clip LED indicators no longer stay lit when the amplifier is in standby.
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PCB Assembly PL380 (100V) from February 2008–, continued QSC Part # Description Qty. Reference Comments CO-000098-00 HEADER, 0.1" CENTERS, 26 POS (2X13), MALE, LATCHING BOX SHORT J8A, J8B CO-000106-00 JACK, HD15, 15 POS, FEMALE, RIGHT ANGLE SWAGED JACK SCREW CO-000148-00...
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PCB Assembly PL380 (230V) (QSC part # WP-038001-02) from February 2008– Revision notes: This revision results in the following changes in performance or operation. • The amplifier no longer goes into standby when the Basis unit shuts off. • The clip LED indicators no longer stay lit when the amplifier is in standby.
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PCB Assembly PL380 (230V) from February 2008–, continued QSC Part # Description Qty. Reference Comments CO-000106-00 JACK, HD15, 15 POS, FEMALE, RIGHT ANGLE SWAGED JACK SCREW CO-000148-00 XLR, NEUTRIK, 3 POS, FEMALE, VERTICAL J3, J4 CO-000155-00 HEADER, 0.1" CENTERS, 2 POS (1X2), MALE, RAMP LOCK...
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