Stereo amplifier circuit diagram and descriptions - using IRFB4020 MOSFETs

A. General Notes.
a. AC voltage thresholds: operate at above 70 V and shutdown at below 50 V.
b Idle current: 120V and 230V @ 0.2A; short limit current: less than 1A per CH

c. Firmwares (FW): four revisions as follow:
f. Service Bulletin:
1. Service bulletin #KSE0001revA, Issue date: Oct 2009,
Title: K Series inductor reinforcement. L13
g. Troubleshoot hints:
1. Power supply failures:
- No blown MOSFETs Q13 & Q14. Check for broken/cracked lead of inductors L11, L12, L13.
. Idle current: 120V and 230V @ 0.2A; short limit current: less than 1A per CH
1. FW Rev A - Initial release.
2. FW Rev B - Increased turn on mute time to avoid signal passing when the system powers off with certain AC input situations.
3. FW Rev C - Increased the fan turn on voltage because some fans wouldn't come on at the initial startup voltage.
4. FW Rev D - Adjusted fan thresholds to accommodate hardware changes and modified limiters based on amplifier updates.
Notes:
FW Rev D IS NOT compatible with older amplifiers which have FW Rev A-C and vise versa amplifier with FW Rev D cannot be downgrade to earlier FW revisions (A-C).
d. K-Series power amplifier is class D, so passive low-pass filter (Audio Precision AUX-0025) is required for all measurements - power, %THD, etc.
e. Circuitry revisions.
1. ECO# 9377, Rev B, Eff. date: Jul 2009:
- Change R141 and R143
2. ECO# 9457, Rev C, Eff. date: Aug 2009:
- Change C13, C14, C25, R73, R77, R173, & FW rev D. Add D15, D16.
Due to circuitry changes on both DSP and Power boards, new and old revisions are incompatible and require correct firmware revision.
- Blown MOSFETs Q13 & Q14. Always replace both MOSFETs and diodes D33 & D34
2. Blown MOSFETS outputs of Amplification circuit:
- Always replace both MOSFETs on the defective channel. If the amplifier still has problem, check its driver - U5 for Q2 & 3 and U7 for Q4 & Q5.

B. Top Box Power Module with DSP feature disabled. To disable DSP, pull out the GAIN B knob, use a install a shunt across pins 2 & 4 if header J7 has 10 pins (early K Series production with PCB rev A & B, till Feb 2010) or across
a. Setup: * Apply a 10 mVrms, 1k Hz sine wave to only XLR input of MIC/LINE IN A; set only GAIN A control fully up; set MIC/LINE switch to LINE.
* K & KW Output Adapter (SG-000576-TS): set the MODE switch to BYPASS. Do not apply any load on the HF channel if the adapter is not available to avoid overloading the HF channel.
b. Output measurements:
1. Output = 1.0 Vrms; LF output and HF output are 180 degree out of phase.
2. Turn the MIC/LINE switch to MIC position.
3. Verify an increase of 24.5 dB gain (16.75 Vrms).
4. Turn both gain controls down. Disconnect the signal from LINE IN A’s input and feed the same signal onto either RCA input. Turn only GAIN B control fully up and verify each output (should be 2 Vrms). Repeat this step to check other RCA input.
5. Turn gain control B down. Disconnect input from RCA and then feed the signal into LINE IN B’s XLR input. Change the input amplitude to 300mV. Turn GAIN B control fully up. Verify output on each channel; should be 101 W @8-ohm with <0.2% THD or 28.5 Vrms
6. Change the input amplitude to 560 mV. Verify output on each channel; should be 358 W @8-ohm with <1.0% THD or 53 Vrms. Note: red LIMIT LED turns on; it is normal.
pins 4 & 6 if header J7 has 6 pins

C. Sub Box Power Module with DSP feature disabled. To disable DSP, pull out the GAIN knob, locate W2 on the right side of the gain pot, and temporarily short two pads of W2 together by soldering a piece of wire on them.
a. Setup:

Apply a 600 mVrms, 1k Hz sinewave to only XLR input of MIC/LINE IN A; Turn GAIN control fully up

b. Output measurements:
1. Output power in bridge (two channel outputs are combined) should be 425 W @8-ohm with <0.2% THD or approximately 58 Vrms

3. Change the input amplitude to 800 mV. Verify output power; it should be 760 W @8-ohm with <1.0% THD or approximately 78 Vrms.

Schematic and PWB

DSP & EEPROM

Input stage

Power amplifier

Power supply (SMPS )

Common parts:
a. K Sub
SP-000183-00 WOOFER,12",PAPER,,,FERRITE,
WP-003310-00 AMP ASSY, KSUB, UNIV SPLY, FULL RNG, PWRD
WP-003314-00 ENTIRE BOARD ASSY. (POWER SUPPLY BOARD)
WP-000334-TS PCB ASSY,INPUT,KSUB,,
b. K8
SP-000180-00 WOOFER, 8", PAPER, FERRITE
WP-003307-00 AMP ASSY,MAIN,K8,UNIVERSAL SUPPLY,
WP-003311-00 PCB ASSY,,K8,UNIVERSAL SUPPLY,
WP-000331-TS PCB ASSY,INPUT,K8,,
c. K10
SP-000181-00 WOOFER, 10", PAPER, FERRITE
WP-003308-00 AMP ASSY, 10", k10, UNIV SPLY, FULL RNG, PWRD
WP-003312-00 PCB ASSY,,K10,UNIVERSAL SUPPLY,
WP-000332-TS PCB ASSY,INPUT,K10,,
d. K12
SP-000182-00 WOOFER, 12", PAPER, FERRITE
WP-003309-00 AMP ASSY, k12, UNIV SPLY, FULL RNG, PWRD
WP-003313-00 PCB ASSY,,K12,UNIVERSAL SUPPLY,
WP 000333-TS PCB ASSY,INPUT,K12,,
e. Common Parts to all models
CO-000386-00 JACK,IEC,3 POS,FEMALE,LOCKING (all models)
SP-000184-00 COMPRESSION DRIVER,1.75",,,PETP,NEODYMIUM,
SR-000145-00 DIAPHRAGM, CELESTION T5510/R, 8 OHM
WC-000361-GP POWER CORD,IEC V-LOCK,18AWG, 3M,,NEMA 5-15,120V
WC-000362-GP POWER CORD,IEC V=LOCK,0.75MM, 3M,,CEE 7/7,230V
WP-000367-00 FAN ASSY,,BOP-2CH,, (all models)
IC-000382-30 DSP 28/56 BIT, , ADAU1701, , U10
IC-000413-30 DRIVER, IRS20957, SMT, U5, U7
QD-000284-00 MOSFET, 600V, 26A, 313W, STW26NM60, TO-247, Q14
QD-000312-GP LED, 3MM, BLUE SP, SLR343BB T 225419 ROHM, , ,
QD-000363-30 DIODE, 30V, 2.0A, , MBR230, SOD-123, D23, D24, D38, D39
QD-000372-00 BRIDGE RECTIFIER,KBU1005, IN-LINE, 600V 10A, BR1
QD-000373-00 MOSFET, 200V, 18A, 100W, IRFB4020, TO-220AB, Q2-Q5
QD-000376-00 MOSFET, 600V, 11A, 160W, STP11NM60FD, TO-220, Q13
QD-000391-00 DIODE, 600V, 8A, FFP08S60S, TO-220, 15NS, D33, D34
QD-000394-10 TRANSISTOR NPN,50V, 2A, 0.9W, 2SC2655, TO-92, Q16, Q7
XF-000376-00 INDUCTOR, CM, TOROID, 4MH, BOP, , 50/60HZ 6.3AL, 11, L12
XF-000377-00 INDUCTOR, 60HZ PFC, TOROID, 774UH, BOP, L13