QSC K.2 Series Service Manual
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QSC K.2 Series Service Manual

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Service Manual
Product Models:
Document #:
Initial Release:
Revised Release:
Revision:
K.2 Series
K8.2, K10.2, K12.2
TD-001517-01
March 2018
A
QSC, LLC
Costa Mesa, California, USA
www.qsc.com

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  • Page 1 Service Manual K.2 Series Product Models: K8.2, K10.2, K12.2 Document #: TD-001517-01 Initial Release: March 2018 Revised Release: Revision: QSC, LLC Costa Mesa, California, USA www.qsc.com...
  • Page 2 QSC, LLC...

  • Page 3: Table Of Contents

    8.10 Input section failure ..........................................46 8.11 Fan issues and overheating ......................................... 46 8.12 Front LED ..............................................47 8.13 Internal wiring harness......................................... 47 8.14 Transducer issues ..........................................48 9. Schematics, exploded-view drawings, and BOM ........................49 TD-001517-01 K.2 Series Service Manual...
  • Page 4 K.2 Series Service Manual Copyright © 2018 by QSC, LLC. All Rights Reserved. QSC and the QSC logo are trademarks of QSC, LLC in the U.S. Patent and Trademark Office and other countries. Patents may apply or be pending. Windows® is a registered trademark of Microsoft Corp.

  • Page 5: Introduction

    1.4 Service bulletins At the publish date of this service manual, two service bulletins concerning the K.2 Series have been issued. Check the QSC Service Partner Portal or contact QSC Technical Services Group (TSG) for the latest information on applicable service documents.

  • Page 6: Serial Numbers

    (The first digit is an individual factory code, and the fourth through ninth digits are the sequential identifying number for each individual unit.) The K.2 series is manufactured in 2 different factories “V” and “G”. Month...

  • Page 7: Product Specification And Images

    M10 Kit-C, K.2 LOC (Lock-Out Cover) K8.2 Yoke K10.2 Yoke K12.2 Yoke Peak SPL is measured on-axis at 1 m, with dynamic pink noise. With product registration. Visit qsc.com for full details. Specifications subject to change without notice. TD-001517-01 K.2 Series Service Manual...

  • Page 8: Firmware & Software

    K.2 Updater application, you must download a newer version of the K.2 Updater applica- tion to peform a firmware update. If in doubt, always download the most recent K.2 Updater from the QSC website. QSC, LLC...

  • Page 9: Test Mode Application

    8-9V, which causes major issues in the amplifier MOSFET gate drivers. In Standby mode, this voltage naturally drops to 8-9V because the PSU is in “Passive (RC) Clamp” mode. The 3.3V and 5.0V rails should be steady and not swing by more than 100mV. TD-001517-01 K.2 Series Service Manual...
  • Page 10 Enabling Test Mode using the K.2 Test Mode application 1. Download the latest K.2 Test Mode application (in .zip format) from the QSC website. 2. Extract the contents of the zip file into a new folder on your computer. 3. View the contents of the new folder. Three files (K2TestMode.exe, SLABHIDDEVICE.dll, and SLABHIDtoSMBus.dll) should exist in the folder.

  • Page 11: Operational Description

    4. Operational description 4.1 Series description The QSC K.2 Series represents the best-in-class loudspeaker for today’s demanding audio professionals. The perfect com- bination of elegant design, superior audio performance, high functionality, simple and intuitive operation, and genuine QSC reliability, K.2 delivers extraordinary results for users in both portable and installed applications.

  • Page 12: Amplifier Module

    Startup sequence The startup sequence for K.2 series is similar to the original K series. The PWM controller at U15 charges itself up when AC voltage is present above a certain threshold, approximately 85 Vac. Once U15 has charged up, the switch mode power supply (SMPS) is switched on.
  • Page 13 1 PCNT 250VAC Figure 4.3.3 - Active flyback converter circuit used in the K.2 series SMPS Auxiliary voltages of ±15V, ± 5V, and +12VLOW are created with separate transformer windings from the main secondary rails, but all windings are tied together at ground. Under load, the amplifiers will pull energy from the main rails and the power supply will increase the duty cycle to compensate and keep the main rails at ±77V;...
  • Page 14 Another pair of wires goes to the front LED which is mounted in the loudspeaker cabinet. Figure 4.3.7 - Top and bottom sides of the AMP/PSU board, showing the locations of the major Class D components QSC, LLC...
  • Page 15 LCD board at connector J1:pin4. The 5V bus on the microUSB connector does not provide any power to other circuits in the amplifier module, and is only monitored by the Figure 4.3.9 - LCD board USB/I2C controller. TD-001517-01 K.2 Series Service Manual...
  • Page 16 DSP actively attenuates the signal down to the upper limit of what the amplifier channels can handle. There are several different limiting scenarios that are proprietary to QSC which cannot be further discussed here.

  • Page 17: Loudspeaker Disassembly & Repair Instructions

    5. Loudspeaker disassembly & repair instructions To reduce the number of pages in this service manual, all K.2 Series loudspeakers have been combined into one section. The K10.2 powered loudspeaker is referenced for generic disassembly and repair procedures. The K8.2 and K12.2 models are assembled nearly identical to the K10.2.
  • Page 18 5. Fasten 6 plastite screws that secure the amplifier module to the speaker cabinet. See Figure 5.1.2. 6. Fasten 2 machine screws, including the rubber feet, into the amplifier module. See Figure 5.1.1 Amplifier module installation is now complete. QSC, LLC...

  • Page 19: Front Grille

    5. Verify that the small gap between the sides of the main enclosure and the baffle are even. Both sides of the front grille must fit inside these gaps. 6. Fasten the screws that secure the baffle to the enclosure, starting with the corner screws. See Figure 5.3.1. TD-001517-01 K.2 Series Service Manual...

  • Page 20: High Frequency Transducer

    6. Place the cover back on the transducer assembly. Figure 5.4.3 - Diaphragm removal with HF Fasten the 4 screws to secure the cover on the transducer assembly. transducer still fastened to baffle Transducer installation Simply follow the removal instructions in reverse. QSC, LLC...

  • Page 21: Low Frequency Transducer

    • Reapply a small amount of thread locking fluid to the mounting Figure 5.6.1 - Handle, screws, and mounting plates plate when replacing the handles. inside the enclosure. TD-001517-01 K.2 Series Service Manual...
  • Page 22 • The pole-cup piece can be removed from the exterior of the speaker enclosure. Access to the interior is not required. • Reapply a small amount of thread locking fluid to the nuts when replacing the pole-cup piece. • Refer to Figure 5.6.3. Figure 5.6.3 - Pole cup piece and mounting plate inside the enclosure QSC, LLC...

  • Page 23: Amplifier Module Disassembly & Repair Instructions

    If the thread is marred or stripped inside, the plastic back cover could vibrate when in use. TD-001517-01 K.2 Series Service Manual...

  • Page 24: Amp/Psu Board

    10. Remove the 7 short machine screws that secure the PCB to the heatsink chassis. See Figure 6.2.6. Figure 6.2.4 - AC wiring harness Figure 6.2.5 - Metal cover removal/installation steps Figure 6.2.6 - Metal cover rotated up for AMP/PSU access QSC, LLC...
  • Page 25 5. Fasten the 2 long machine screws at a torque of 28.8 kgf-cm (25 in-lbs). Important note: The torque specification on these 2 screws is very critical to ensure good heat transfer between the electrical component and heatsink. Sufficient clamp force is required to achieve the best result. TD-001517-01 K.2 Series Service Manual...
  • Page 26 15. Lightly tighten the 2 zip ties that were installed in step 6 and trim excess. 16. Connect the 3 ribbon connectors as shown in Figure 6.2.2. Verify that the fan and front LED 2-conductor wires are connected to the appropriate locations. QSC, LLC...

  • Page 27: Input/Dsp Board

    6. Install the 3 gain knobs and 1 rotary encoder knob (if removed) to their appropriate locations. See Figure 6.3.1. Connect all 5 ribbon cables back to their original locations on the input/DSP board as shown in Figure 6.2.2. TD-001517-01 K.2 Series Service Manual...

  • Page 28: Lcd Board

    4. Remove the 2 nuts from the threaded standoffs using a 7mm wrench or nut driver. See Figure 6.5.1. 5. Lift the EMI shield out of the chassis and set aside. Figure 6.5.1 - EMI shield assembly in amplifier chassis QSC, LLC...
  • Page 29 Important note: AC wire routing and placement is very critical. If these installation steps are not done correctly, the AC line could induce noise and cross-talk into the input/DSP circuits. Figure 6.5.3 - Faston connection through power switch Figure 6.5.4 - AC wiring guideline through EMI shield cutouts TD-001517-01 K.2 Series Service Manual...

  • Page 30: Fan

    8 kgf-cm (7 in-lbs). Do not over-torque. 4. Follow installation steps 6 — 16 in “6.2 AMP/PSU board” on page 24 to reassemble the amplifier module. Figure 6.6.1 - Fan assembly to metal cover. QSC, LLC...

  • Page 31: Amplifier Module Reference

    6.7 Amplifier module reference Use the reference below as a visual aide for reassembly of the amplifier module. The amplifier module should look like this before installing the back cover to the amplifier chassis. TD-001517-01 K.2 Series Service Manual...

  • Page 32: Testing

    Wire harness p/n K8.2 WC-000613-00 K10.2 WC-000614-00 Figure 7.1.2 - K.2 Series test adapter with dual binding K12.2 WC-000615-00 post connectors, made from a K.2 wire harness. *Any wire harness part number can be used as a test adapter for all models...

  • Page 33: Amplifier Module Testing

    8. Plug the amplifier module into a variac and set up an AC line current monitor. 9. Turn the K.2 power switch on. Figure 7.2.2 - Setup diagram for all K.2 amplifier models. This test setup also includes a distortion analyzer. TD-001517-01 K.2 Series Service Manual...
  • Page 34 Note: The PSU may shut down intermittently before it can run steadily and safely in output short condition. Verify the AC line current draw; it should drop below 1.0A. 8. Remove the short and verify the amplifier module recovers into 2▲Ω. 9. Turn the gain control A to minimum and continue next test. QSC, LLC...
  • Page 35 6. Run this test for 5 minutes and then stop. Verify that fan increases in speed as heat sink temperature rises. You can hear the fan noise near the front heat sink, behind the QSC logo. Switch the test load to OFF and let the amplifier cool down for at least 2 minutes.

  • Page 36: Loudspeaker Testing

    7.3 Loudspeaker testing Once a K.2 Series loudspeaker is fully assembled it must be tested to meet all audio specifications. This final step is re- quired to verify that the amplifier module powers the transducers, no distortion is present, and that the speaker meets SPL specifications.
  • Page 37 Step or sweep the generator frequency from about 20 Hz up to about 20 kHz. Listen for a clean, undistorted tone; any buzzes, rattles, distortion, etc., could indicate a defective transducer, loose hardware, damaged enclosure, or other problem that must be corrected. TD-001517-01 K.2 Series Service Manual...

  • Page 38: Troubleshooting Tips

    8. Troubleshooting tips For additional troubleshooting information on K.2 Series powered loudspeakers, please see the “K.2 Series Service Trouble- shooting Guide” document available on the QSC Service Partner Portal. QSC will frequently revise the Troubleshooting Guide document as new common failures are found.

  • Page 39: Testing The Ac Mains Fuse And Line Filter Components

    • If an open-circuit is measured, NTC inrush resistor R41 is probably broken or open. Alternatively, inductor L41 or L42 could also have broken leads. Figure 8.2.2 - Measurement locations for testing the AC line filter board components TD-001517-01 K.2 Series Service Manual...

  • Page 40: Bypassing The Ac Line Filter

    AC input. Figure 8.3.2 - Custom AC wiring harness for K.2. Add a resettable 3A circuit breaker in series for added protecetion (not pictured). Figure 8.3.1 - Bypassing the AC line filter using a custom AC wiring harness QSC, LLC...

  • Page 41: Power Supply Mosfets And Repair

    1 PCNT 1/16W R157 STP45N65M5 QM_DR C124 R150 1 PCNT 10.0K 1/16W 0.0022UF 1 PCNT 20 PCNT 1/8W 250VAC PRI_LO 220PF 10 PCNT 250VAC Figure 8.4.2 - Some components to check if the MOSFETs fail. TD-001517-01 K.2 Series Service Manual...

  • Page 42: Amplifier Mosfets

    3.57K 1 PCNT 1.0UF 1.0UF 1/16W R113 10PCT 10PCT 100.0VDC 100.0VDC ES1D 2.87 1 PCNT 1/10W ES1D 2.87 1 PCNT 1/10W LF_VSS 47UF 20 PCNT 100V Figure 8.5.2 - Components to check if amplifier MOSFETs fail (LF shown) QSC, LLC...

  • Page 43: Lf And Hf Amplifier Leds

    F1 to blow. The -15V rail will also measure 0▲Vdc if F1 is open. • SMD MOSFET Q16 could be the culprit. Q16 is located on the bottom side of the AMP/PSU board. Also check the Schottky diodes in the circuit as highlighted in Figure 8.7.1. TD-001517-01 K.2 Series Service Manual...

  • Page 44: Testing The Input/Dsp And Lcd Boards

    +3.3VD rail (which powers the MCU and DSP). If the LED is pulsing, check the +15V input from the AUX power supply, the buck regulator components, and circuits that use the +3.3VD rail. Figure 8.8.3 - LED locations and associated voltage rails QSC, LLC...

  • Page 45: Lcd Ribbon

    • If you find any issues with the LCD ribbon or connector, it’s best to just replace the entire LCD board with a new one. • Do not try to fix the ribbon cable or connector TD-001517-01 K.2 Series Service Manual...

  • Page 46: Input Section Failure

    • After repairing, pay close to the gain section when bench testing the amplifier module 8.11 Fan issues and overheating A functional fan is required for normal use of the K.2 series. If the fan does not work, the amplifier module will easily overheat, go into thermal protec- tion, and shutdown the amplifiers.

  • Page 47: Front Led

    2 kHz. If one of the transducers is discon- nected internally because of the wiring harness, it will be very obvious with the sine-wave sweep. TD-001517-01 K.2 Series Service Manual...

  • Page 48: Transducer Issues

    8.14 Transducer issues There are many different types of failures for transducers in K.2 series loudspeakers. The most common issues found are the following: spider becomes unglued from the frame, cone tears near the surround, burnt voice coil (because of an ampli- fier module failure), and voice coil rubbing on edge of magnet.

  • Page 49: Schematics, Exploded-View Drawings, And Bom

    Please download these supplemental documents from the Service Partner Portal at www.qsc.com/login (registration and login are required) or contact QSC for them. The Service Partner Portal is always up-to-date with the latest information and service documents.
  • Page 50 Contact information Service manuals and other service documents are available for download from www.qsc.com via the Service Partner Portal. If you need any further information regarding this service procedure, please contact QSC Technical Services at the addresses or numbers below.

This manual is also suitable for:

K8.2K10.2K12.2

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