qsc_plx-1202,plx-1602,plx-2402,plx-3002 电路图.pdf

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1、Technical Service Manual PLX Series LLLLLPLX 1202 LLLLLPLX 1602 LLLLLPLX 2402 LLLLLPLX 3002 TD-000078-00 TD-000078-00 RadioFans.CN 收音机爱 好者资料库 + PLX 1202 + PLX 1602 + PLX 2402 + PLX 3002 RadioFans.CN 收音机爱 好者资料库 PLX SERIES SERVICE MANUAL PLX 1202 PLX 1602 PLX 2402 PLX 3002 QSC Technical Services Wats:

2、 I -%OO-772-2034 Local: 1-714-957-7150 Fax: 1-714-754-6173 QSC Technical Support BBS I -714-668-7567 1-800-856-6003 QSC Audio Products, Inc. 1675 MacArthur Blvd. Costa Mesa, CA 92626 RadioFans.CN 收音机爱 好者资料库 Table of Contents PLX Product Specifications . Introduction . Test and Calibration . Troubles

3、hooting PLX . PLX Parts List . . . . . . . . . . . . . . . . PLX Semiconductors . Chassis Drawings . Schematics . . . . PLX Series PCB Circut Board Drawings . 1 2 3 13 PLX 1202 PCB Assembly (120V)23 PLX 1202 PCB Assembly (230V)25 PLX 1202 Chassis Assembly (120V)28 PLX 1202 Chassis Assembly (230V)28

4、PLX 1602 PCB Assembly (120V)28 PLX 1602 PCB Assembly (230V)31 PLX 1602 Chassis Assembly (120V)34 PLX 1602 Chassis Assembly (230V)34 PLX 2402 PCB Assembly (120V)35 PLX 2402 PCB Assembly (230V)38 PLX 2402 Chassis Assembly (120V)41 PLX 2402 Chassis Assembly (230V)41 PLX 3002 PCB Assembly (120V)42 PLX 3

5、002 PCB Assembly (230V)45 PLX 3002 Chassis Assembly (120V)48 PLX 3002 Chassis Assembly (230V)49 50 53 PLX 1202 Main PCB Schematics57 PLX 1602 Main PCB Schematics62 PLX 2402 Main PCB Schematics67 PLX 3002 Main PCB Schematics72 73 PLX Product Specifications PLX 1202 PLX 1602 PLX 2402 PLX 3002 PLXI 202

6、PLXI 602PLX2402 PLX3002 Output Power (per channel): Continuous Average Output Power both channels driven: 8ohms,2OHz-2OkHz,0.03%THD 200 watts 4ohms,2OHz-2OkHz,0.05%THD 325watts Con0nuous Average Output Power bridged mono ooeration: 300waKs 425 watts 550 watts 500watts 700watts 900 watts 8 ohms, 2OHz

7、 - 2OkHz, 0.1% THD Voltage Gain (dB) Sensitivity (for rated power 8 ohms) Distortion Frequency Response (LF Switched Off) Damping Factor (1 kHz and Below) Noise Input Impedance Dimensions Faceplate Width Faceplate Height Chassis Depth Weight Net, Lbs/kg 700 iatts 1100 watts 1500 watts 32 32 32 1.00v

8、rms 1.20 Vrms 1.50 Vrms SMPTE-IM Less than 0.01% 2OHz to 2OkHz, +I-0.2dB 8Hz to 5OkHz, +Ol-3dB Greater than500 106dB below rated output (20 Hz to 20 kHz) 6k unbalanced, 12k balanced 2000 watts 32 1.70 vrms Standard 19” Rack Mounting 3.Y3.r 13.2Y13.2v 2119.5 2119.5 3.5” 3.Y 13.2Y13.2Y 2119.5 2119.5 I

9、ntroduction This manual is prepared to assist service personnel with the repair and calibration of PLX power amplifiers . The procedures described in this manual require advanced technical experience and sophisticated audio test equipment. CAUTION: To reduce the risk of electric shock, do not remove

10、 the cover. No user-serviceable parts inside. Refer servicing to qualified personnel. CAUTION WARNING: To prevent fire or electric shock, do not expose this equipment to rain or moisture. Documentation This manual contains schematics, printed circuit board (PCB) drawings, parts lists, and mechanical

11、 assembly drawings. This information should be used in conjunction with the test and troubleshooting guide. The electrical and electronic components are identified by circuit identification numbers on the schematics and the parts list. The test s is s/;ghf/y less for 240V. Pause at 9OVAC (2OOVAC Eur

12、opean) for three seconds until the mute I protect circuit disengages. Continue to 12OVAC (24OV European). Verify that the fan is operating at low speed. 3. Turn the power switch off and on a few times to verify the 3 second power-up muting delay. . CHANNEL OUTPUT 1. Look for amplified signal on the

13、scope for channel 1. Switch the input signal and scope to channel 2 and repeat output test. Check for noisy / contaminated gain pots by observing general instability on the distortion waveform while adjusting the gain control levels. 2. Select an 8 ohm load and confirm that this amplifier is produci

14、ng 300 watts at 1 kHz just below the point of clipping. Check both channels. . BRIDGE MODE 1. Turn the power switch off. 2. Set Mode Switch #7 in the on position. The gain control, limiter, and filter switch positions on CH2 are disabled with Mode Switch #7 on. 3. Set load to both red output binding

15、 posts (CHI positive and CH2 negative). 4. Apply a 1.30 VRMS, 1 kHz sinewave input to channel 1 of the amplifier. Check the power and verify that the output does not immediately collapse. Check for 1000 watts at 8 ohms. 5. Turn power off and place the amplifier under test back into the Stereo mode w

16、ith output loads connected to each channel. l B I A S I. Let the amplifier cool down to room temperature. 2. With an input amplitude of 1.3OVrms increase the input frequency to 20kHz. Reduce the input signal 20dB (80%) from full output. Adjust the crossover trimpot VR43 (CHl) and VR166 (CH2) for abo

17、ut a 4OOmVpk-pk crossover spike protruding from the noise trace on the oscilloscope. It will be necessary to have the oscilloscope measure unfiltered distortion from the amplifier in order to see the crossover spike.It is necessary to disable the 80kHz lowpass filter on the analyzer for this test. F

18、urther trim so that the total distortion for that channel is less than 0.1% THD+N. 3. With the trim settings achieved, and with no signal plugged into the amplifier and with an 8 ohm load, verify that the AC idle current from the AC service is no more than 1 .O amperes. 4. Let the amplifier cool dow

19、n and check channel 2. l SHORT CIRCUIT CURRENT 1. Select a 2 ohm load and apply a 1.3Vrms sinewave (1 kHz) input signal to both channels of the amplifier. Ensure that power is on and that the gain controls are fully up. 2. While the amplifier is producing power into the loads, apply a short to the o

20、utput binding posts of each channel.In other words, apply a jumper between the red and black binding posts of each channel. Once this is done, combined AC line current draw for both channels should be no greater than 13A ac. This is with a 120 volt AC service to the amplifier. Current may be lower i

21、f AC line voltage is lower. 3. Remove the short from each channel and verify that the channels recover in to 2 ohm loads. The output should not experience any hang up and a full sinewave should be present just as it was before a short was applied for this test. 4. If the amplifier does not pass any

22、of the above steps, troubleshoot the current limit section of the amplifier. If steps 2, 3, and 4 above pass, continue to the next test FREQUENCY RESPONSE. 6 l FREQUENCY RESPONSE I. Set load to 8 ohms and scale the input generator to gain 1 watt of power from the amplifier on each channel. Gain cont

23、rols on the amplifier should be fully up. 2. Check frequency response from 2OHz to 20kHz (+I- 0.2OdB) by sweeping random frequencies between these extremes. This is done by verifying the same voltage amplitude at each of the frequencies selected (within 2OHz to 20kHz). Check both channels. l POWER v

24、s. DISTORTION TEST 1. Check to ensure that both channels will produce rated power at 2OHz, 2KHz, and 20kHz. into an 8 ohm load. 2. While verifying rated power, check that at all frequencies the distortion measurement is less than or equal to 0.03% THD. l THERMAL TEST 1. Set input frequency to 1 KHz

25、and short both channels while they are producing power into a load. 2. Apply a short to the output of each channel. 3. AC line current draw should be about II - 13.5 amperes for both channels. As the amplifier gets hot, there will be some current drift upwards and the fan speed will increase. This i

26、s not a problem as long as the case temperature on the output transistors does not exceed 105 degrees C. 4. Verify that the NTC circuit causes thermal shutdown after an extended period. 5. When thermal shutdown occurs, verify AC idle current of less that 0.90 amperes. l CM TEST 1. Select an 8 ohm lo

27、ad and confirm that this amplifier is producing rated power. 2. Check the Common Mode of the amplifier by inserting a 1/4” input jack halfway into each channel and observe about 6 dB of output voltage reduction. There will also be a 180 degree phase inversion at the output of the channel under test.

28、 l OUTPUT NOISE I. Set the amplifier gain controls all the way up, with a 1 kHz 1.3OVrms sinewave input signal.Note the output level at full power just below clipping. Adjust gain if needed. 2. Remove the input signal connector from the amplifier and measure the residual noise level produced into th

29、e load by the amplifier. The noise signal should be 107 dB down from the full output power point measured. A signal to noise ratio should be better than or equal to 107dB. Check both channels. l FINAL CHECK This completes the amplifier test procedure for this model. Inspect the amplifier for mechani

30、cal defects. inspect the solder connections. Reassemble the amplifier and veri the amplifiers operation before returning the product to service. PLX 2402 Test Procedure l SET-UP 1. Connect a test load to the output terminals of the amplifier. 2. Make sure Mode Switches 1 - 10 are in the default posi

31、tion (1 on, 10 on, all others off). 3. Connect a distortion analyzer with a resolution of O.Ol%, 20-20kHz (or better) to the output terminals of the amplifier. Enable the 80kHz low pass filter. 4. Connect a dual-channel oscilloscope to the following test points: Chl - a 1OX (vertical sensitivity - 2

32、V/cm) scope probe to the channel speaker output. Ch2 - a IX scope probe (vertical sensitivity - 0. IV/cm) to the distortion analyzer output. 5. Set amp gain pots fully clockwise and turn on power switch. 6. Connect the output of the signal generator to the input terminals of the amplifier and select

33、 an output of 1.50 VRMS 1 kHz sine wave. 7. Plug the amplifier into a variac and set up an AC line current monitor. l POWER UP Q73, Q74, Q79 8, Q80) IGBTs 8 their associated components may fail 14 CHECK EMITTER AND BASE RESISTORS WHILE DEVICES ARE REMOVED, Each output transistor has an associatated

34、pair of 0.47 ohm resistors in parallel. Each BANK of output transistors has a 15 ohm resistor from base to rail (emitter bus). Audio Outputs, Troubleshooting Current Limit WEAK CURRENT LIMIT - PREMATURE CLIPPING. The usual symptom of weak output current is premature clipping of one or more peaks of

35、the audio voltage. This could be caused by missing step, weak current limit, or dead output section. PREMATURE CLIPPING at 60% VOLTAGE, SIMILAR AT ALL IMPEDANCES: This points to a step problem (2402, 3002 only). See Step Troubleshooting. If the amplifier reaches full voltage at 8 ohms, but premature

36、ly clips at 4 ohms or 2 ohms, we can assume the step is OK but the output current is too low (see below). NO OUTPUT AT ALL ON ONE POLARITY. This indicates complete failure (open circuit) in the circuit leading to the dead output polarity. Check the series components in the current splitter for missi

37、ng or open: Ch 1: Positive, Ql9, R381, Q20, R70, DIO, D14. Negative: Q22, R382, Q21, R71, Dl I, D12 Ch 2: Positive, Q64, R383, Q65, Rl93, D35, D39. Negative: Q67, R384, Q66, Rl94, D36, D37 CONSTANT, PREMATURE CLIPPING, WORSE AT LOW IMPEDANCES. First, check the clamping voltages on C21 (Ch I+), C22 (

38、Ch I-), C56 (Ch 2+), C57 (Ch 2-), as shown in table below. At idle, all four voltages should all be similar. If one is out, check parts according to the following table CLAMPING VOLTAGES ARE WRONG AT IDLE CHANNEL-POLARITY Measure voltage on: 3002 and 2402, about 6V. 1602, about 4,6V, 1202 about 4.9V

39、. Voltage too high: missing resistor: or missing transistor: Voltage 0-0.3V: shorted transistor or missing resistor Voltage 0.7V, missing resistor: Voltage wrong: wrong value CH I+ CH l- c21 c22 R60 Q14 Ql4,24 R 51, 72 R59 R59,60 R61 Ql5 Ql5, 25 R53, 75 R62 R62,61 CH 2+ C56 RI83 Q59 Q59,69 Rl74, 195

40、 RI82 Rl82, 183 CH 2- c57 RI84 Q60 Q60,70 Rl76, 198 RI85 Rl85,184 The exact voltage varies with temperature. Look for the mismatching value on the weak cell. A too-low voltage causes early clamping of that output section, as explained in the previous several pages. If the voltage is correct and curr

41、ent is still low, also check for missing - unsoldered output device, or emitter resistors. 15 Audio Power Stage, Current Limit Troubleshooting CURRENT LIMITS WHICH COLLAPSE PREMATURELY. An immediate collapse of ALL current limits at full power could be premature triggering of “Power Supply Cutback”,

42、 which is described in the section below. Cutback after several seconds of full power operation at two ohms is normal. Cutback of one or more output sections, at full temperature, while approaching full power into two ohms is also normal. However, cutbacks at 4 ohms, or when cold into two ohms, indi

43、cate problems with the transistor power measuring circuitry. CLAMPING VOLTAGES COLLAPSE TOO SOON. CHANNEL-POLARITY CH I+ CH l- CH 2+ CH 2- Measure voltage on: c21 c22C56 c57 Cuts back too easily: low value, R67, 73 R68, 74Rl90, 196Rl91, 197 or high value: R 51, 72 R53, 75Rl74, 195Rl76, 198 or missin

44、g diode: D9 D8 D34 D33 CLAMPING VOLTAGES ARE CORRECT, CURRENT STILL WEAK. Shorted diodeDIO, 14Dll, 12D35, 39 D36, 37 Missing-unsoldered output device or emitter resistor. TROUBLESHOOTING “POWER SUPPLY CUTBACK”. As noted in the section on Power Supply, the amplifiers current limit cuts back when necessary to protect the power supply. Because the Observed effect is a reduced output voltage, in response to prolonged operation above the long-term current limit, we commonly refer to this behavior as “power supply cutback”, but we must remember that it is actually amp/Tier current