QSC CX Series Service Manual
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QSC CX Series Service Manual

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CX Series
C X 4
CX12

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Summary of Contents for QSC CX Series

  • Page 1 CX Series C X 4 CX12...
  • Page 2 CX Series CX4T CX1 2T...
  • Page 3 CX SERIES AMPLIFIER SERVICE MANUAL CX4 - CX4T CX6 - CX6T CX12 - CX12T QSC Technical Services Wats: 1-800-772-2834 Local: 1-714-957-7150 Fax: 1-714-754-6173 QSC Online! Online Computer Information System 1-800-856-6003 I-71 4-668-7567 QSC Audio Products, Inc. 1675 MacArthur Blvd. Costa Mesa, CA 92626...
  • Page 5 CX Series Chassis Drawings CX4 Chassis Assembly ..............42 CX4T Chassis Assembly ..............45 CX6 & CX12 Chassis Assembly y ............48 CX6T & CX12T Chassis Assembly y ............ 48 CX 4 / 4T Display Board Schematic ..........39 CX 6T & 12T Display Board Schematic ..........39 CX4 /4T Series Main Amplifier Board ..........
  • Page 7 .a’- CX Series -ww.,_- ~ CX Series Product Specifications *-“-” *“arT‘ CX12 Output Power (per channel): Continuous Average Output Power both channels driven: 8 ohms, 20Hz 20kHz, 0.1% THD 150 watts 200 watts 400 watts 4 ohms, 20Hz 20kHz, 0.1% THD...
  • Page 8 CX Series Product Specifications CX Series CX4 T CX12T CX4T CX6T CX12T Output Power (per channel): Direct Output, watts per channel, both channels driven: 8 ohms, 45H.z 20kHz, 0.1% THD 150 watts 200 watts 400 watts 4 ohms, 45Hz 20kHz, 0.1% THD...

  • Page 9: Factory Repair

    When in doubt, you may contact QSC Technical Services for assistance. Parts orders to QSC should include the product model number, the part description, and the QSC part number (from the parts list in this manual). Parts will be shipped via UPS, F.O.B. Costa Mesa, California, Shipping, handling and COD charges may be added to the cost of the parts.

  • Page 10: Suggested Test Equipment

    Audio Precision test and procedures files are made available, free of charge, from QSC Technical Services by either sending a self addressed stamped envelope and a 3 1/2” disk to QSC, or by logging on to QSC Online and downloading the appropriate files.

  • Page 11: Channel Output

    e s t & C a l i b r a t i o n NOTE: This test procedure will refer to the amplifier’s channels as Ch 1 (Channel 1) & Ch2 (Channel 2). Component designation will have the prefix “5” for Ch 1 and “6” for Ch2. CX4 / CX4T Test Procedure S E T - U P 1.

  • Page 12: Short Circuit Current

    CX Series 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. Further trim R512 so that the total distortion for that channel is at about 0.1% THD+N. If bias is not adjustable, see the bias description and troubleshooting section of this manual, 3.

  • Page 13: Frequency Response

    g. After the short circuit current is set and even clipping is achieved, re-apply the short to the output to reconfirm AC line current. If the current draw is not within the range specified, again balance the current limit trimpots until even clipping and the correct AC current draw is met.

  • Page 14: Final Check

    CX Series 2. Remove the input signal connector from the amplifier and measure the residual noise level produced into the load by the amplifier. The noise signal should be 100 dB down from the full output power point measured. A signal to noise ratio should be better than or equal to 100dB.
  • Page 15 CX Series 5 Turn power off and place the amplifier under test back into the Stereo mode with output loads connected to each channel. Reinsert CH2 input plug and turn both gain controls fully up. BIAS ADJUSTMENT 1. Let the amplifier cool down to room temperature, 2.
  • Page 16 CX Series e. Once the correct AC current draw is set, remove the short on the output, When this is done, the output power should spring back into the 4 ohm load. If it does not, the current limits are set too low.
  • Page 17 CX Series FINAL CHECK This completes the amplifier test procedure for this model. Inspect the amplifier for mechanical defects. Inspect the solder connections. Reassemble the amplifier and verify the amplifier’s operation before returning the product to service. CX12 / CX12T Test Procedure S E T - U P Connect a test load to the output terminals of the amplifier.
  • Page 18 CX Series BIAS ADJUSTMENT 1. Let the amplifier cool down to room temperature. 2. With an input amplitude of 1Vrms, increase the input frequency to 20kHz. Reduce the input signal 20dB (80%) from full output. At this point, a couple of watts of output power should be observed at the output.
  • Page 19 channels the same for a change in current limiting. Both wipers need to adjust evenly to achieve a balanced setting. e. Once the correct AC current draw is set, remove the short on the output. When this is done, the output power should spring back into the 4 ohm load. If it does not, the current limits are set too low.
  • Page 20 CX Series OUTPUT NOISE 1. Set the amplifier gain controls all the way up, with a 1 kHz 1 .00Vrms sinewave input signal, Note the output level. 2. Remove the input signal connector from the amplifier and measure the residual noise level produced into the load by the amplifier.

  • Page 21: Current Draw

    CX Series T r o u b l e s h o o t i n g Current Draw (Circuit breakers and fuses blow. Burning smell or smoke) Symptoms: Excessive current without signal present Fast current draw Medium current draw .
  • Page 22 CX Series Protection, Standby, and Power Up. (The amplifier locks up or does not startup and shut off correctly) Model CX4/4 T Symptoms: Amplifier does not come out of protect Amplifier will not thermally protect Muting delay Pilot LED not working Fan doesn’t work...
  • Page 23 CX Series CX6/6T & CX12/12T Possible Causes: AMPLIFIER DOES NOT COME OUT OF PROTECT 1. Check speaker bus for DC; if over 3VDC present, the protection circuit is operating normally to hold of operation. See DC FAULT WITHOUT CURRENT DRAW section to fix this DC fault.

  • Page 24: Faults With Signal Present

    CX Series 5. Replace LD501 if voltage is less than 1.5V SHUTS OFF UNDER SIGNAL 1. C517 missing, defective, or much too small DC FAULT WITHOUT CURRENT DRAW In most cases, shorts in the output circuit will cause current draw, but certain shorts will only cause DC offset in the output.
  • Page 25 CX Series 6. Defective gain control “RINGING’ SOUND WITH NO INPUT TO AMPLIFIER 1. C518, C519, C523 open or wrong value. (CX4/T) C505, C516. 2. R541, R542, R538, R547 open or wrong value. (CX4/T) R523, R524, R502. 3. Defective op amp U503. (CX4/T) U501 4.
  • Page 26 CX Series 2. No step: check 0503, Q504, U501, U502 burned to open. R505, R506, R510 open. Instability (Gain problems, spurious noises, and oscillations) All Models General Output Distortion Excessive or unbalanced crossover Output waveform appears “fuzzy” Possible Causes: First, distinguish between instability (fuzziness), “ringing” which is momentary instability after a transition, "step”...
  • Page 27 CX Series Power Supply and Voltage Rail Balancing (Uneven rails and power supply problems) Symptoms: Current limiting wrong Current limiting too high into a short . IC rail too high into a short Current limiting too low into a short...
  • Page 28 CX Series CX Series Voltage Conversion PARTS REQUIRED FOR 120 V OPERATION FROM 230V (Please refer to CX Series wiring diagrams in this manual for AC Voltage drawings) Model CX4/4T Part Number Description Reference LB-00005200 LABEL, cUL APPROVAL CHASSIS SERIAL LABEL...
  • Page 29 -a’*.,. . ,, , CX Series Voltage Conversion PARTS REQUIRED FOR 230 V OPERATION FROM 12OV (Please refer to CX Series wiring diagrams in this manual for AC Voltage drawings) Model CX4/4T Part Number Description Qty R e f e r e n c e...
  • Page 30 CX Series CX Series Voltage Conversion PARTS REQUIRED FOR 1 OOV OPERATION FROM 12OV (Please refer to CX Series wiring diagrams in this manual for AC Voltage drawings) Model CX4/4T Part Number Description Reference PS-O00038xI0 SERIAL LABEL CHASSIS NOTE: 1. Remove the cUL label on the rear panel 2.
  • Page 31 2. Replace the serial label with appropriate VOLTAGE and CURRENT listings. CX Series Voltage Conversion PARTS REQUIRED FOR 1 0 0 V OPERATION FROM 230V (Please refer to CX Series wiring diagrams in this manual for AC Voltage drawings) Model CX4/4T Part Number Description...
  • Page 32 3. Place a 30A FUSE label on the AC PCB, overlapped the 15A fuse label CX Series Voltage Conversion PARTS REQUIRED FOR 230V OPERATION FROM 1OOV (Please refer to CX Series wiring diagrams in this manual for AC Voltage drawings) Model CX4/4T Part Number...
  • Page 33 HW-060001-00 BRACKET,#6-32, THD, RT ANGLE IC-000032-00 Ic LIN M P ~c3317aP D U A L LB-0001 12-00 LABEL, INPUT, CX SERIES NW-040400-06 NUT KEPS 4-40 NW-06041 O-ET PT-3 10002-00 RES VAR 1 T 1 OK 20% 0.2W W/DET QD-000062-10 XISTOR NPN TO-92 40V 0.2A 1.5W...
  • Page 34 CX6 Display Board Assembly CX4 Display Board Assembly WP-000048-00 CX 4 DISPIAY ASSY WP-000944-00 CX 6 DISPLAY ASSY Part Number Description Part Number Description Reference Reference C A P CER 4 7 P F 1 0 % 1OOV N P O R E F E R E N C E P C - 0 0 0 0 4 8 - 0 0 C A - 2 3 3 0 0 1 - 1 0...
  • Page 35 Cl 06,206 8 PIN IC SOCKET HEADER PCB 2 X 7 .l X .l BOX HEADER 2 X 8 VERT PC-000944-00 DISPLAY PCB, CX SERIES SPACER RND NYL#6 0.385”L BLK REF: LDlOl LED GRN T-l LED YEL T-l LED RED T-l...
  • Page 36 XISTOR PNP TO-3P 200V 15A LED RED T-l 3/4 VOLTAGE REF XISTOR NPN TO-3P 200V 15A DIODE RECT DO41 400V 1 A QSC WIRE 1026, 4.25”, WHITE WC-001 026.TQ DIODE SWITCH DO35 75V 75MA WC-I .5022,.IW INDUCTOR 2UH 18AWG VERT MNT L500,600...
  • Page 37 CX6 / CX6T Main Board Assembly CX6 / CX6T Main Board Assembly (Cont’d) WP-000113-00 MAIN PCB ASSY CX6 WP-000113-00 MAIN PCB ASSY CX6 Part Number Description Reference Part Number Description Reference CA-01 8001-10 CAP SM 16PF 5% 500V RES VAR IT 2K 20% 0.15W CARB CA-027001-10 CAP SM 27PF 10% 500V CA-047001 -10...
  • Page 38 CX Series CX6 / CX6T Main Board Assembly (Cont’d) WP-000113-00 MAIN PC6 ASSY CX6 / CX6T Part Number Description RES MF 75,OK 1% l/4W RN-1 22002.BM RN-21 0002-BM RN-31 0002.BM SC-062050.PP SC-081 101.SP SW-000550-00 WIRE JMPR SO 0.1” WC-0.2020.JW WC-0.5018.JW .5” JUMPER, WHT., 18 GA, SOLID WC-1.2518.JW...
  • Page 39 WP-000123-00 MAIN PCB ASSY CX12 I CXl2T Part Number Description Reference REF: LD501 CA-010001-10 CAP CER 1OPF 10% 1OOV PT-11 OOOO-AT RES VAR IT 100 20% 0.15W CARB CAP SM 18PF 5% 500V CA-018001-10 RES VAR IT 2K 20% 0.15W CARB CA-047001-10 CAP CER 47PF 10% 1 OOV NPO XISTOR NPN TO220 200V 1A...
  • Page 40 CX Series CX12 / CXl2T Main Board Assembly (Cont’d) WP-000123-00 MAIN PCS ASSY CX12 Part Number Description Reference RES MOFP 22 5% 1 W RES CF 1 K 5% 1/4W RES CF 2.7K 5% 1/4W RES MOFP 3K 5% 2W RES MOFP 3.9K 5% 5W...
  • Page 41 CX4 Finished & Chassis Assembly (12OV) CX4 Finished & Chassis Assembly (230V) CX4 CHASSIS ASSY (1 ZOV) CX 4 CHASSIS ASSY (230V) Part Number Description Reference Part Number Description Reference RACK EAR, SLS PLATFORM RACK EAR, SLS PLATFORM CH-14021 O-BX 1400 KNOB FABRICATION CH-14021 O-BX 1400 KNOB FABRICATION...
  • Page 42 20V) CX 4T CHASSIS ASSY (12OV) WP-000054-02 CX 4T CHASSIS ASSY (230V) Par-l Number Description Reference Part Number Description Reference RACK EAR, SLS PLATFORM RACK EAR, SLS PLATFORM 1400 KNOB FABRICATION CH-14021 O-BX 1400 KNOB FABRICATION CO-000096-00 CONN BARRIER 5-POS W/COVER CO-000096-00 CONN BARRIER 5-POS W/COVER CO-0001 OO-OO CONN PLUG 7.PIN EURO BLK...
  • Page 43 LABEL, cUL APPROVAL LB-00005440 LABEL, WARNING, TOP COVER LB-000053-00 LABEL, CE LISTING LB-000054-00 LABEL, WARNING, TOP COVER LABEL, REAR, OUTPUT CX SERIES LB-000 114-00 LABEL, REAR, OUTPUT CX SERIES LB-0001 23-00 LABEL, FACEPLATE CX6 LB-0001 23-00 LABEL, FACEPLATE CX6 LABEL, FUSE, UL CAUT. 12A 250V...
  • Page 44 CABLE ASSY 16 COND RIB. 28’ LG WC-00001 6-oO 6 c0~D . 2au L G C A B L E WC-000069-00 WIRE ASSY, OUTPUT, CX SERIES WC-000069-00 WIRE ASSY, OUTPUT, CX SERIES WC-00 110 1 SQ QSC SLEEVE WC-00 110 1 SQ QSC SLEEVE 1101,5”, CLEAR...
  • Page 45 CONN PLUG 7.PIN EURO BLK CONN PLUG 7.PIN EURO BLK LB-000052-00 LABEL, cUL APPROVAL LABEL, CE LISTING LB-000053-00 LB-0001 14-00 LABEL, REAR, OUTPUT CX SERIES LB-0001 14-00 LABEL, REAR, OUTPUT CX SERIES LB-0001 25-00 LABEL, FACEPLATE CXI 2 LB-0001 2500 LABEL, FACEPLATE CXlZ LB-160226-01 LABEL, FUSE, UL CAUT.
  • Page 46 CABLE ASSY 14 COND RIB. 10” LG WC-00001 6-00 CABLE ASSY 16 COND RIB. 28” LG CABLE ASSY 16 COND RIB. 28” LG WC-000069-00 WIRE ASSY, OUTPUT, CX SERIES WC-00001 6-00 WC-001 lOl-SQ QSC SLEEVE 1101,5’, CLEAR WC-000069-00 WIRE ASSY, OUTPUT, CX SERIES...

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