QSC K.2 series User manual

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

2QSC, LLC

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TD-001517-01
K.2 Series Service Manual
Table of Contents
1. Introduction..................................................................................................................................................................................5
1.1 Restriction of Hazardous Substances Directive (RoHS) ...................................................................................................................................................... 5
1.2 Revision history......................................................................................................................................................................................................................... 5
1.3 Service manual contents.......................................................................................................................................................................................................... 5
1.4 Service bulletins ........................................................................................................................................................................................................................ 5
1.5 Serial Numbers.......................................................................................................................................................................................................................... 6
1.6 Required equipment for service ............................................................................................................................................................................................. 6
2. Product specification and images ................................................................................................................................................7
3. Firmware & software....................................................................................................................................................................8
3.1 Firmware revision history ....................................................................................................................................................................................................... 8
3.2 Firmware update instructions................................................................................................................................................................................................. 8
3.3 Test Mode application.............................................................................................................................................................................................................. 9
4. Operational description ............................................................................................................................................................. 11
4.1 Series description.....................................................................................................................................................................................................................11
4.2 Model descriptions..................................................................................................................................................................................................................11
4.3 Amplifier module.....................................................................................................................................................................................................................12
5. Loudspeaker disassembly & repair instructions ....................................................................................................................... 17
5.1 Amplifier module .....................................................................................................................................................................................................................17
5.2 Front grille ................................................................................................................................................................................................................................19
5.3 Front baffle...............................................................................................................................................................................................................................19
5.4 High frequency transducer.................................................................................................................................................................................................... 20
5.5 Low frequency transducer .....................................................................................................................................................................................................21
5.6 Handles, feet, and pole mount..............................................................................................................................................................................................21
6. Amplifier module disassembly & repair instructions ...............................................................................................................23
6.1 Back cover................................................................................................................................................................................................................................ 23
6.2 AMP/PSU board...................................................................................................................................................................................................................... 24
6.3 Input/DSP board..................................................................................................................................................................................................................... 27
6.4 LCD board................................................................................................................................................................................................................................ 28
6.5 EMI shield and AC line filter board...................................................................................................................................................................................... 28
6.6 Fan ............................................................................................................................................................................................................................................ 30
6.7 Amplifier module reference...................................................................................................................................................................................................31
7. Testing.........................................................................................................................................................................................32
7.1 Requirements........................................................................................................................................................................................................................... 32
7.2 Amplifier module testing........................................................................................................................................................................................................ 33
7.3 Loudspeaker testing................................................................................................................................................................................................................ 36
8. Troubleshooting tips...................................................................................................................................................................38
8.1 General tips.............................................................................................................................................................................................................................. 38
8.2 Testing the AC mains fuse and line filter components...................................................................................................................................................... 39
8.3 Bypassing the AC line filter ................................................................................................................................................................................................... 40
8.4 Power supply MOSFETs and repair.......................................................................................................................................................................................41
8.5 Amplifier MOSFETs................................................................................................................................................................................................................. 42
8.6 LF and HF amplifier LEDs...................................................................................................................................................................................................... 43
8.7 +12VLOW voltage rail failures............................................................................................................................................................................................... 43
8.8 Testing the input/DSP and LCD boards ............................................................................................................................................................................... 44
8.9 LCD ribbon............................................................................................................................................................................................................................... 45
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

4QSC, LLC
QSC, LLC
Technical Services Group
1675 MacArthur Blvd.
Costa Mesa CA 92626 USA
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.
Audio Precision® is a registered trademark of Audio Precision, Inc.
All other trademarks are property of their respective owners.
[phone]
1-800 QSC AUDIO (USA only)
[phone] (fax)
www.qsc.com (main web site)
www.qsc.com/login (Service Partner Portal login)
www.qscparts.com (parts and accessories sales)

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TD-001517-01
K.2 Series Service Manual
1. Introduction
1.1 Restriction of Hazardous Substances Directive (RoHS)
QSC K.2 Series powered loudspeakers are manufactured to conform to the European Union’s RoHS Directive, which reduc-
es 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 elec-
tronic components, solder, and other parts.
RoHS-compliant materials
When 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 tools
Soldering 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 history
No revision history yet. First revision released March 2018.
1.3 Service manual contents
Starting late 2017, QSC changed the key contents inside the Service Manual. Because hardware or software may under-
go several changes during the life of this product, schematic diagrams, PCB images, and full BOM are not available in this
service manual. This new structure will reduce the overall page count and number of revisions, making the service manual
easier to navigate.
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.
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.
These service bulletins apply to K.2 series loudspeakers that should be noted:
• K2-001: No power. Applies to K8.2, K10.2, and K12.2 with serial date code VAHxxxxxx - VHHxxxxxx / GAHxxxxxx - GH-
Hxxxxxx. A very small percentage of K.2 powered loudspeakers built before September 2017 may not power up, either
when first turning on the speaker or after some use. The speaker could fail quietly or make a popping sound. After the
failure occurs, the amplifier module, which is located on the back of the speaker, is completely non-functional.
• K2-002: No audio coming out of standby / chirping sounds. Applies to K8.2, K10.2, and K12.2 with serial date code
VAHxxxxxx - VIHxxxxxx / GAHxxxxxx - GIHxxxxxx. A very low percentage of K.2 powered loudspeakers could experience
symptoms of no audio while coming out of standby, no audio after being turned on, or random chirping/buzzing sounds.
The issue is more susceptible to high amplifier module temperatures and AC input voltages in the range of 125▲V -
140▲V or 250▲V to 280▲V.

6QSC, LLC
1.5 Serial Numbers
Serial numbers on QSC K.2 Series powered loudspeakers are nine digits long. The second
digit represents the month of manufacture, and the third digit represents the year; use
the decoder chart on the right to find the manufacture date. (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”.
For example, a serial number of VDHxxxxxx would indicate that the product was built at
factory “V” in 04/17, or April 2017.
The unit’s serial number can be found on a label near the power inlet.
Important Note: The serial number is also stored in the flash memory on the input/DSP board. The K.2 Updater utility (a
Windows application) can be used to view the serial number. However, if the input/DSP or amplifier module was replaced,
the serial number in flash memory will not match the serial number on the label shipped with the product. Due to this fact,
it’s recommended to only use the physical serial number label in reference to the product’s warranty. If in doubt, please
contact QSC for further assistance.
1.6 Required equipment for service
Hardware and Software
• Personal computer (PC) running Windows® 7 or newer operating system with available USB2.0 or newer port
• K.2 Updater utility (not always required)
• USB Type A to microUSB cable
Tools required
• Various hand tools for electronic repair, including Phillips (#1, #2, extra long #2), flat (#2) and Hex (#4, 7mm, 9/32”)
screwdrivers, putty/butter knife, needle-nose pliers, etc.
• 2.5x or higher magnifier with lamp
• ROHS-compliant (lead-free) soldering iron, desoldering equipment, and solder
Service bench setup
• Custom K.2 series test adapter (for amplifier module bench testing)
• Non-inductive load resistors, configurable as 16Ω(min. 225 watts capacity), as 2Ω(min. 1000 watts capacity).
• XLR male and female cables
• Digital multimeter (DMM) with RMS AC voltage and current
• Oscilloscope (two or more traces, mixed signal, 250 MHz or higher) with digital frequency display
• Balanced signal tone generator, capable of 20 Hz to 20 kHz sine-wave and pink/white noise
• Grounded anti-ESD mat, wrist or ankle strap
GDH0T6879
K12.2 ASSEMBLED IN CHINA
VDH0U8796
K10.2 ASSEMBLED IN CHINA
Xm y xxxxxx
Month Year
G = 2016
H = 2017
I = 2018
J = 2019
K = 2020
L = 2021
M = 2022
N = 2023
O = 2024
A = Jan
B = Feb
C = Mar
D = Apr
E = May
F = Jun
G = Jul
H = Aug
I = Sep
J = Oct
K = Nov
L = Dec

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TD-001517-01
K.2 Series Service Manual
2. Product specification and images
1
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.
K8.2 K10.2 K12.2
Configuration: Multi-purpose, 2-way powered loudspeaker
LF Transducer: 8" (203 mm), cone 10" (254 mm), cone 12" (305 mm), cone
HF Transducer: 1.4" (35.6 mm) titanium diaphragm compression driver
Frequency Response (-6 dB): 59 Hz - 20 kHz 56 Hz - 20 kHz 50 Hz - 20 kHz
Frequency Range (-10 dB): 55 Hz - 20 kHz 50 Hz - 20 kHz 45 Hz - 20 kHz
Nominal Coverage Angle: 105° Axisymetric 90° Axisymetric 75° Axisymetric
Maximum Rated SPL1: 128 dB Peak 130 dB Peak 132 dB Peak
Amplifier: Class D
Peak: 1800 W (LF), 225 W (HF)
Cooling: Low-noise, variable speed fan
Controls: Power
3 x Level
Rotary encoder
2 x selection buttons
Indicators: Monochrome LCD Display 1.75" x 1" (45 mm x 25.4 mm)
2 x Power LED (front and rear)
3 x Input Signal LED
Input A MIC selected LED
Input B HI-Z selected LED
Limiter active LED
Connectors: 2 x locking XLR/F ¼" combo (Mic/Line Input and Hi-Z/Line Input
1 x 3.5 mm TRS (Stereo Input)
2 x XLR/M (Loop-thru Output)
1 x XLR/M (Mix Output)
1 x locking IEC power connector
AC Power Input: Universal power supply 100 – 240 VAC, 50 – 60 Hz
AC Power Consumption 1/8th Power: 100 VAC, 2.1 A • 120 VAC, 1.9 A • 240 VAC, 1.1 A
Enclosure Details
Enclosure Enclosure: Impact Resistant ABS
Attachment Points: 2 x M10 threaded inserts plus integrated Pull-Back
Color: Black (RAL 9011)
Grille: 18 Gauge powered coated steel, internal cloth lining
Dimensions (H x W x D): 17.7 x 11 x 10.6 in 20.4 x 12.6 x 11.8 in 23.7 x 14 x 13.8 in
449 x 280 x 269 mm 519 x 320 x 300 mm 602 x 356 x 350 mm
Net Weight: 12.2 kg (27 lbs) 14.5 kg (32 lbs) 17.7 kg (39 lbs)
Shipping Weight: 14.4 kg (31.8 lbs) 17.6 kg (38.8 lbs) 21.7 kg (47.8 lbs)
Regulatory: CE, WEEE, UL, China RoHS, RoHS II, FCC Class B
Optional Accessories: K8 Tote, K8 Outdoor Cover K10 Tote, K10 Outdoor Cover K12 Tote, K12 Outdoor Cover
M10 Kit-C, K.2 LOC (Lock-Out Cover) M10 Kit-C, K.2 LOC (Lock-Out Cover) M10 Kit-C, K.2 LOC (Lock-Out Cover)
K8.2 Yoke K10.2 Yoke K12.2 Yoke
K.2 Series Specifications

8QSC, LLC
3. Firmware & software
3.1 Firmware revision history
Current revision at the publication of this service manual (December 2017) is: v1.0.8.5
Firmware revision Release date Notes
1.0.8.5 Pilot • Initial (Pilot) K.2 firmware release
3.2 Firmware update instructions
Requirements
• Windows PC only (native MAC OS not supported)
• USB Type A to microUSB cable
• AC power cord
Scenes
Saved user scenes (input selector setting, preset selection, crossover, delay, EQ, LED, and contrast) are stored in a different
flash memory location. These scenes should remain saved and load fine after a successful firmware update.
Updating firmware using the K.2 Updater application
1. Download the latest K.2 Updater 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 (K2Updater.exe, SLABHIDDEVICE.dll, and
SLABHIDtoSMBus.dll) should exist in the folder.
4. Connect the AC power cord to the power inlet on the K.2 amplifier module.
5. Remove the rotary encoder knob (to the right of the LCD screen).
6. Connect the USB Type A to microUSB cable. The Type A end connects to your computer’s USB port and the microUSB
end connects to the port above the rotary encoder part on the K.2.
7. Turn the amplifier module on by flipping the power switch.
8. Open K2Updater.exe by double-clicking on the file/icon. The K.2 Updater application provides information about the
K.2 device in the table.
9. If an update is needed, a button to update the firmware
will appear under the “Actions” column. If no update is
needed, “Firmware up to date” will appear instead.
10. Click the Update button to proceed with the firmware
update.
Caution: Do not disconnect the USB cable or remove
power from the amplifier module during an update!
11. After the update is complete, power cycle the amplifier
module and verify the firmware version matches the K.2
Updater version.
Note: If you receive the message “Please update application. Firmware more recent”, then the K.2 Updater application is
an older version than the firmware version detected in the K.2 amplifier module. Because individual firmware files are
stored and encoded in the 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.
Figure 3.2.1 - K.2 Updater application in Windows OS.

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K.2 Series Service Manual
3.3 Test Mode application
In some cases it may be useful to place the amplifier module into “Test Mode” for bench testing or troubleshooting. To
enable Test Mode, use the K.2 Test Mode application on a Windows OS.
Enabling Test Mode removes DSP limiting, voicing, and EQ. This allows us to test the amplifier module to full power specifi-
cations. Please keep in mind the following when using Test Mode:
• DSP limiting is disabled, which allows the maximum output voltage and power to both channels.
• DSP voicing and EQ (including the 2▲kHz crossover between channels) is disabled. All frequencies can pass through both
LF and HF output channels, providing a mostly flat response output.
• Test Mode should only be used when the amplifier module is disconnected from the K.2 speaker enclosure (effectively
disconnecting the LF and HF transducers from the system). If Test Mode is enabled when the drivers are connected to the
amplifier module and an active input signal is present, there is a risk of damaging the drivers!
Requirements
The hardware and software requirements for the Test Mode application are similar to the K.2 Updater application.
• Windows PC only (native MAC OS not supported)
• USB Type A to microUSB cable
• AC power cord
Test Mode functions by page
Page / Function Description
TEST MODE
TEMP External temperature reading from temperature sensor (location U8 on the AMP/PSU board, bottom side nearest the heatsink).
MCU TEMP Internal temperature reading in the Cortex microcontroller die (location U2 on the input/DSP board).
ACV AC voltage reading from AC voltage monitor circuit (location U9 on AMP/PSU board).
STAND BY
AUTO (Default). Start-up timer, AC dead zone, and DC dead zone will places amps in standby. (Not the same as normal Standby mode.)
AMPS ON Amplifiers always on. Ignore any condition that can put the amplifiers in standby mode.
FAN MODE
OFF Fan all the way off - 0%
LOW Fan at low speed - 50%
HIGH (Default) Fan at high speed - 100%
TEMP TEST
OFF (Default) Temperature test off.
START Run temperature test. During the test the DSP applies a high level pink noise to the amp channels while the temperature is
measured for 45 seconds. If temperature significantly increases, returns a “Pass”. If temperature does not increase, returns a “Fail”.
Primarily used to determine if the temperature sensor U8 is working, but can also be useful to check output.
BURN IN
OFF (Default) Burn in test off.
ON Burn in test on. Commands the DSP to apply a high level pink noise to both amp channels (no timeout).
POWER TEST
OFF (Default) Power test off.
ON Power test on. Adds an LF RMS limiter through the DSP signal path and connects the limit LED to that limiter. The mode allows for
long term power testing.
CROSSOVER TEST Should be renamed to “Cross Talk Test”.
BOTH (Default) Both channels on.
HF / LF OFF High frequency channel ON. Low frequency channel OFF.
LF / HF OFF Low frequency channel ON. High frequency channel OFF.
POWER SCREEN
+15V, -15V, 3.3V, 5.0V Measures power rails. If the ±15V rails drop below ±12.3V in RUN mode, this could cause the +12VLOW voltage rails to drop to
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.
Proceed with caution while in Test Mode

10 QSC, LLC
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.
4. Connect the AC power cord to the power inlet on the K.2 amplifier module.
5. Remove the rotary encoder knob (to the right of the LCD screen).
6. Connect the USB Type A to microUSB cable. The
Type A end connects to your computer’s USB port
and the microUSB end connects to the port above
the rotary encoder part on the K.2.
7. Flip the power switch on the amplifier module to
turn it on.
8. Open K2TestMode.exe by double-clicking on the
file/icon. The K.2 Test Mode application provides
information about the K.2 device in the table.
9. To enable Test mode, click on the slider button to
move it from Disabled to Enable.
10. Power cycle the amplifier module by turning the
power switch off, waiting at least 2 seconds, and turning the switch back on.
11. If Test Mode was successfully enabled, the LCD screen will show the Test Mode home
screen as shown in Figure 3.3.2 and the amplifier module’s fan running in high speed.
Caution!: Once Test Mode is enabled, do not apply any signal until the amplifier mod-
ule has been disconnected from the speaker loads. Failure to do so could result in
over-driven LF or HF transducers because DSP limiting is disabled. Only use resistive
test loads while in Test Mode.
Disabling Test Mode using the K.2 Test Mode application
Always disable Test Mode before returning the amplifier back to service. Follow the instructions below.
1. Repeat steps 4 through 8 in the section above.
2. To disable Test mode, click on the slider button to move it from Enable to Disabled.
3. Power cycle the amplifier module by turning the power switch off, waiting at least 2 seconds, and turning the switch
back on.
4. If Test Mode was successfully disabled, the LCD screen will show the default K.2 home screen. See Figure 3.3.3.
Figure 3.3.1 - Enabling or disabling Test Mode.
Figure 3.3.2 - Test Mode home
page on LCD.
Figure 3.3.3 - Default home page. Always
disable Test Mode after returning to service.