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TD-001517-01
K.2 Series Service Manual

Table of Contents

1. Introduction ..................................................................................................................................................................................5

2. Product specification and images ................................................................................................................................................7

3. Firmware & software ....................................................................................................................................................................8

4. Operational description ............................................................................................................................................................. 11

5. Loudspeaker disassembly & repair instructions ....................................................................................................................... 17

6. Amplifier module disassembly & repair instructions ...............................................................................................................23

7. Testing .........................................................................................................................................................................................32

8. Troubleshooting tips...................................................................................................................................................................38

9. Schematics, exploded-view drawings, and BOM ......................................................................................................................49

Summary of Contents for K10.2

Page 1: ...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...

Page 2: ...2 QSC LLC...

Page 3: ...cy 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...

Page 4: ...d 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 tr...

Page 5: ...al 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...

Page 6: ...uct 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 avai...

Page 7: ...lected LED Input B HI Z selected LED Limiter active LED Connectors 2 x locking XLR F 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 Outpu...

Page 8: ...icroUSB 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 powe...

Page 9: ...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...

Page 10: ...er 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 amp...

Page 11: ...r with QSC black RAL color 9011 The front grille is 16 gauge steel and finished with black powder coat to best match the enclosure color Behind the grille is the main baffle of the speaker The baffle...

Page 12: ...ry side of the transformer the microcontroller MCU and DSP will begin to boot All audio outputs are muted in the DSP until the voltages at the AC monitor circuit at U9 and a couple other internal volt...

Page 13: ...PCNT 500V 0 022UF 500V 0 022UF 0 022UF 500V 200V KBU1005 10 PCNT 1N4148 100K 10K 1W 5 PCNT 10K 5 PCNT 5 PCNT 10K 1W 1 8W 10 PCNT 1W 5 PCNT RB751S40T1 10 10K 100K 1 8W 0 0022UF 10 RB751S40T1 1 16W STP1...

Page 14: ...DC 1 0UF 10PCT 1 0W IRFB4227PBF 1 10W 10 1 PCNT 20 PCNT 47UF 100V 1UH 47UF 1UH 20 PCNT 100V 50V 5 PCNT 10 1 21K 1 PCNT 1 16W 1 16W 1 PCNT 5 62K RB751S40T1 1 16W 1 16W 1 PCNT 698 5 PCNT 500 0 VDC 2K 9...

Page 15: ...I2C controller DSP_RST_L FAN_GND AMP_SD_L LEDS_ON LINE_INST_SEL_N MIC_LINE_SEL 2 5VREF MIX_OUT_P MIX_OUT_N MIX_OUT2_P MIX_OUT2_N LINE_INST_SEL_P LEDS_ON_C CS_L_DSP TEMP_SENS LCD_BACKLIGHT SDA_I2C SCL_...

Page 16: ...ion and bias affecting the voltage at LINEUV in the active clamp flyback controller U15 pin 15 The second circuit is an AC voltage monitor The output of the monitor U9 pin7 is read by both the DSP and...

Page 17: ...hey vary between models All torque values can be found in the Exploded View drawings Each component that requires proper torque has a square box with a reference number next to the item number A legen...

Page 18: ...sual aide 8 Fully remove the amplifier module from the enclosure Installation 1 Prepare to insert the amplifier module into the speaker cabinet 2 With one hand holding the wiring harness and the other...

Page 19: ...e 3 Partially lift the baffle assembly away from the main enclosure to separate them 4 Disconnect the molex connector from the rear of the amplifier module inside the cabinet 5 You may now fully remov...

Page 20: ...be pressed to release the connector from the speaker tab 2 Remove the 4 screws 4 lock washers and 4 normal washers that secure the HF transducer to the baffle See Figure 5 4 2 3 The HF transducer can...

Page 21: ...ng tab to the wiring harness if the old ones are weak or not functional 3 Gently lower the LF transducer into the speaker assembly also noting the original LF driver orientation the LF tabs should be...

Page 22: ...mounting plate Access to the interior of the speaker assembly is required to remove and install all rubber feet The only way to access the interior of the enclosure is to remove the baffle assembly Se...

Page 23: ...n place 4 Fasten the 1 remaining machine screw to secure the top of the back cover to the amplifier module assembly 5 Fasten the 2 plastite screws to secure the side of the chassis to the back cover F...

Page 24: ...and output connector PCB to provide access to the AMP PSU board See Figure 6 2 6 for a visual aide Troubleshooting tip Leave the cover up in this position while connected to AC power outputting audio...

Page 25: ...4 insulation pads on the heatsink 2 Carefully align and place the AMP PSU board into the heatsink cavity verifying that the body of the power components MOSFETs and diodes on the bottom of the PCB is...

Page 26: ...gh the rubber grommet as shown in Figure 6 2 10 11 Align the output connector board to the metal cover and fasten the 2 machine screws to secure 12 Align the metal cover to the heatsink and verify tha...

Page 27: ...eady mounted 2 Insert the input DSP board into the chassis Important note When mounting the input DSP board into the chassis the latches on the input XLRs must be inserted into the holes on the chassi...

Page 28: ...appropriate locations 4 Place the LCD board into the chassis verifying the buttons are still in place 5 Fasten the 4 machine screws that secure the LCD board to the chassis stand offs as shown in Fig...

Page 29: ...of the AMP PSU board Verify the connector latch is in the locked position Gently tug on the wiring harness to verify sufficient latching EMI shield installation 5 Carefully install the EMI shield into...

Page 30: ...6 1 3 Remove the 2 washers and custom fan bracket 4 Remove the fan from the standoffs and set aside Installation 1 Install the new fan over the standoffs noting the wire position in Figure 6 2 8 2 Pla...

Page 31: ...Service Manual 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 cove...

Page 32: ...D can be tested via the molex jack See the pin out diagram in Figure 7 1 1 K 2 Series test adapter For testing an amplifier module under load or viewing the output waveform on an oscilloscope a test a...

Page 33: ...lter inputs to the output terminals of the adapter 4 Connect the distortion analyzer to the Class D filter Enable the 80k Hz low pass filter 5 Connect a dual channel oscilloscope to the following test...

Page 34: ...ick 120 V only Finally verify the fan does not spin if temperature is less than 50C 6 Verify the amplifier is running with default settings Part 2 Verifying Ch 1 LF 2 OHM POWER vs DISTORTION at 400Hz...

Page 35: ...6 Apply a short to Ch 2 HF output and verify short limit protection 7 Verify the AC line current draw it should drop below 0 5A 8 Remove the short and verify the amplifier recovers into 16 9 Turn the...

Page 36: ...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 See Figu...

Page 37: ...ct to the loudspeaker the relative SPL measured at 5 kHz may be significantly lower Part 3 Measuring peak SPL 1 Set the output of function generator 0 00 Vrms dynamic pink noise 2 Hold the SPL meter 1...

Page 38: ...R147 for approximately 55 Vdc If the PSU does not come out of a pulse skipping mode check for shorted diodes D23 D24 and D51 Also check U2 Q8 and Q7 in the HF amplifier section If excess transformer...

Page 39: ...an to gain access to the AC wiring harness 3 Disconnect the wiring harness from the AMP PSU board and pull the harness out of the heatsink for easy access 4 Turn the power switch ON 5 Using a DMM in m...

Page 40: ...wires Use a rated power switch to apply AC power to the board Hot plugging is not recommended Be very careful of any exposed conductors on the custom wire harness AC is present on these exposed conduc...

Page 41: ...with a new one instead of repairing Check gate drive components resistors and diodes tied to gate signals QM DR and AUX_OUT If the LEDs or LCD screen blink but the module won t start suspect a failur...

Page 42: ...with the failed amp section LF or HF for a shorted or open voice coil MOSFET clamping Take good care during the reassembly process when replacing the power MOSFETs Apply a fresh and thin layer of the...

Page 43: ...audio especially when coming out of standby mode 12VLOW notes If the chirping buzzing sound is heard or there is no audio when coming out of standby please refer to the latest Service Bulletin The AM...

Page 44: ...om the LCD board to their appropriate locations on the input DSP board See Figure 8 8 2 3 Verify all basic functions with the golden LCD board Verify that the rotary encoder buttons and LCD screen wor...

Page 45: ...aw is 130 mA If the MCU is running blue LED LD7 will be steady Major circuits on the input DSP board should work when powering up The MCU DSP LCD and push buttons should all be functional because they...

Page 46: ...uld cause the inductors right after the XLR inputs to fail If all 3 signal LEDs are on without input it may be related to a different failure in the 12VLOW circuit see page 43 After repairing pay clos...

Page 47: ...ing measurements from the rear of the speaker after removing the am plifier module at the 6 pin molex connector can quickly provide information about the condition of the transducers and front LED The...

Page 48: ...orientation of the LF transducer is correct The wire tabs should be at the 2 o clock position Important note When refastening the low frequency transducer to the baffle tighten the screws in a crissc...

Page 49: ...d viewd drawings PCB images and full BOM are not available in this service manual This new structure will reduce the overall page count PDF file size and number of revisions making the service manual...

Page 50: ...please contact QSC Technical Services at the addresses or numbers below Telephone 1 800 772 2834 within USA only 1 714 957 7150 Fax 1 714 754 6173 Web sites www qsc com product info support www qsc c...

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