SUB125/125a

SERVICE MANUAL

Amplifier/Subwoofer

JBL Consumer Products Inc. 250 Crossways Park Drive Woodbury, N.Y. 11797
A Harman International Company

7/2003

SUB125
The SUB125 is part of the SCS125/125a system

TABLE OF CONTENTS

COVER...1 GENERAL SPECIFICATIONS..2 TABLE OF CONTENTS..2 SCS125/125a SPECIFICATIONS..3 CONTROLS AND THEIR FUNCTION..5 SCS125/125a SPEAKER LEVEL CONNECTIONS.6 SCS125/125a LINE LEVEL CONNECTIONS..7 SUB125 TEST SET UP AND PROCEDURE.8 SIMPLE TROUBLESHOOTING..9 Service Bulletin JBL9901..10 SCS125/125a PACKING...11 SUB125 EXPLODED VIEW...12 SUB125 PCB COMPONENT SIDE..13 SUB125 PCB SOLDER SIDE..14 SUB125 ELECTRICAL PARTS LIST.15 SUB125 INTEGRATED CIRCUIT DIAGRAMS.17 SUB125 POWER AMP SCHEMATIC DIAGRAM.18 SUB125 PRE-AMP SCHEMATIC DIAGRAM.19

GENERAL SPECIFICATIONS

SCS125/125a System
Frequency Response 35Hz 20kHz (6dB)
Amplifier. 75 watts RMS Bass. 8" woofer, bass-reflex enclosure Dimensions (H x W x D) 14-1/8 x 13 x 13 inches 359 x 330 x 330mm Weight. 27.5 lbs/12.5 kg Refinements may be made on occasion to existing products without notice, but will always meet or exceed original specifications unless otherwise stated.
SCS125/125a SPECIFICATIONS
LINE VOLTAGE US 120vac/60Hz EU 230vac/50-60Hz Asia 100vac/50Hz Yes/No Yes Yes Yes Spec. Amp Section Type (Class AB, D, other) Load Impedance (speaker) Rated Output Power THD@ Rated Power THD @ 1 Watt DC Offset Damping factor Input Sensitivity Input Frequency Line Input Speaker/Hi Level Input 4.26 Hz mVrms Vrms 50 2dB 2dB Nominal Freq. To Rated Power To Rated Power 1 input driven 1 input driven (-26dB below Line In).1 input driven AB 0.08 0.<200 AB Ohms Watts % % mV-DC DF n/a n/a 80 0.3 0.n/a Nominal 1 input driven 22k filter 22k filter @ Speaker Outputs Sink required for Class AB Z-curve required Hi/Lo Line 108-132 207-264 90-110 Unit Unit Vrms Vrms Vrms Limits Notes Normal Operation Normal operation, MOMS required Normal Operation Conditions Notes
Signal to Noise SNR-A-Weighted SNR-unweighted SNR @ 1W-unweighted Residual Noise Floor Residual Noise Floor 60 1.dBA dBr dBr mVrms 55 2.5 rel. to rated power rel. to rated power rel. to 1W Output A-Weighting filter 22k filter 22k filter
Volume @max, using RMS reading DMM/VOM (or A/P) Volume @max, w/ A/P Swept Bandpass Measurement (Line freq.+ harmonics)

mVrms(max) 2

Input Impedance Line Input Speaker/Hi Level Input Filters Low Pass (fixed or variable) Low Pass filter (point or range) Slope Q Subsonic filter (HPF) Slope Q fixed 1.12 1.4 Hz dB/Octave Damping Hz dB/Octave Damping 2dB n/a n/a 2dB n/a n/a 2 cascaded 2nd order filters of 1.8 &0.7 Q -3dB Point -3dB Point 15K 4.7K ohms ohms n/a n/a Nominal Nominal
Signal Sensing (ATO) Auto-Turn-On (yes/no) ATO Input Frequency ATO Level ATO Bandwidth ATO Turn-on time Auto Mute/ Turn-OFF Time yes 5k Hz mV Hz ms minutes functional functional functional functional functional functional 2mV@50Hz into Line Input w/ 1 ch. driven ATO-LPF for noise immunity T before muting, after signal is removed AC Power Applied DV1 measured 7mV @ 5kHz. 2mV @ 1kHz
Amp connected and AC on, then input signal applied
Power on Delay time Transients/Pops ATO Transient Turn-on Transient Turn-off Transient

functional

mV-peak mV-peak mV-peak
@ Speaker Outputs @ Speaker Outputs @ Speaker Outputs AC Line cycled from OFF to ON AC Line cycled from ON to OFF
Efficiency Stand-by Input Power Power Cons.@rated power Protection Short Circuit Protection Thermal Protection Yes 65 deg. C yes 2 functional functional Direct short at output @1/8 max unclipped Power DC present at Speaker Out leads Type-T or Slo Blo DV1:Plate=50deg.C max.Tab=90deg.C max.T-on =65deg.C Relay or crowbar (for driver/fire protection) External fuse with UL/SEMKO rated holder Watts Watts n/a n/a @ nom. line voltage @ nom. line voltage
DC Offset Protection Line Fuse Rating

functional 2

CONTROLS AND THEIR FUNCTION
SPEAKER LEVEL OUTPUT C L R
SPEAKER LEVEL INPUT C L R

LINE LEVEL

SUBWOOFER LEVEL

MIN MAX

STAND BY

AC 120V~,60Hz 160W

FUSE 2A/250V FUSE
1. Speaker Level Outputs - Connect the Left, Center and Right speakers to these connectors. 2. Speaker Level Inputs - These High Level Inputs are for receivers that do not have line-level pre-amp out or subwoofer out jacks. When a pair of main or satellite speakers are attached to the OUTPUT terminals, they are driven the full range of frequencies as generated by the music source (receiver, amplifier, etc.) 3. Line Level Input - These left and right Line Level Inputs are normally used when the receiver/ processor has line-level pre-amp out or subwoofer out jacks. 4. Auto/On Switch - This switch allows you to set the Mode of the Amplifier. Turn the switch to Auto to cause it to Auto-matically turn on when it receives a signal and Auto-matically turn off after twenty minutes without a signal. If this switch is left On, the subwoofer will always be ON when the power switch is turned On, regardless of input signal.

5. Subwoofer Level - This knob controls the volume level of the SUB125. 6. LED - Red & Green. The LEDs indicate the Mode status that the subwoofer is in. When the SUB125 is turned OFF neither LED will be lit. The Green LED will light when the SUB125 is ON and receiving a signal. The Red LED will light when the amplifier has not received a signal for twenty minutes. The subwoofer will turn on when your receiver/amplifier begins playing again. 7. Power Switch - This the master power switch. Use it (in Off mode) to disconnect power to the amplifier. 8. Fuse - Use only same type of fuses. For the U.S. 120V version use only a 2A 250V fuse. For the European 230V version use only a 1A fuse. 9. AC Cord
SCS125/125a SPEAKER LEVEL CONNECTIONS

Left Front

Center

Right Front

SPEAKER LEVEL INPUT C L R SPEAKER LEVEL OUTPUT C L R

Receiver

Left Front Center Right Front

Left Surround

Right Surround
SCS125/125a LINE LEVEL CONNECTIONS
Center Left Front Right Front

Left Front Subwoofer Out

SUB125 TEST SET UP AND PROCEDURE

CD PLAYER

AC VOLT METER ( 6V )

SPEAKER UNDER TEST

PRE AMP

AMPLIFIER

SPEAKER LEVEL
SPEAKER LEVEL OUTPUT C R L
SPEAKER LEVEL INPUT C R L

SPEAKER

OUTPUT FROM AMPLIFIER

FROM PRE AMP

General Function
UUT = Unit Under Test 1. Connect both right and left line level inputs (RCA) to signal generator and UUT. Use Y-cable if necessary from mono source. VOLUME control should be full counterclockwise. 2. 3. 4. 5. 6. 7. 8. Turn on generator, adjust to 200mV, 50 Hz. Plug in UUT; red LED should be ON. Turn VOLUME control full clockwise. LED should turn Green; immediate bass response should be heard and felt from port tube opening. Turn off generator, turn VOLUME control fully counterclockwise, disconnect RCA cables. Connect one pair of speaker cables to both high level input terminals on UUT. Cables should be connected to an integrated amplifier fed by the signal generator. Turn on generator and adjust so that speaker level output is 3.0V, 50 Hz. Turn VOLUME control full clockwise. Green LED should light, immediate bass response should be heard and felt from the port tube opening.

Sweep Function

1. 2. Follow steps 1-4 above, using a sweep generator as a signal source. Sweep generator from 20Hz to 300Hz. Listen to the cabinet and drivers for any rattles, clicks, buzzes or any other noises. If any unusual noises are heard, remove driver and test.

Driver Function

1. 2. 3. Remove driver from cabinet; detach + and - wire clips. Check DC resistance of driver; it should be 3.3 ohms.
Connect a pair of speaker cables to driver terminals. Cables should be connected to an integrated amplifier fed by a signal generator. Turn on generator and adjust so that speaker level output is 5.0V. 4. Sweep generator from 20Hz to 1kHz. Listen to driver for any rubbing, buzzing, or other unusual noises.

SIMPLE TROUBLESHOOTING

If there is no sound from any of the speakers, check the following:
Receiver/amplifier is on and a source is playing. Powered subwoofer is plugged in and is either in the On or Auto position. Check all wires and connections between receiver/ amplifier and speakers. Make sure all wires are connected. Make sure none of the speaker wires are frayed, cut or punctured. Review proper operation of your receiver/amplifier. If there is no sound coming from one speaker, check the following: Check the Balance control on your receiver/amplifier.
If there is low bass output, check the following:
Make sure the connections to the left and right Speaker Inputs have the correct polarity (+ and ). Powered subwoofer is plugged in and is either in the On or Auto position.
If there is no sound from the surround speakers, check the following:
Check all wires and connections between receiver/ amplifier and speakers. Make sure all wires are connected. Make sure none of the speaker wires are frayed, cut or punctured. Review proper operation of your receiver/amplifier and its surround sound features. Receiver mode must be in Dolby Pro logic, Dolby Digital, or any other mode that creates a surround-sound effect. Even under normal operation, when viewing movies and television, surround sound is not present at all times at a high volume - only when the program has chosen to send information there.
If the system plays at low volumes but shuts off as volume is increased, check the following:
Check all wires and con-nections between receiver/ amplifier and speakers. Make sure all wires are connected. Make sure none of the speaker wires are frayed, cut or punctured. If more than one pair of main speakers is being used, check the minimum impedance requirements of your receiver/amplifier.

Service Bulletin JBL9901

To: All JBL Service Centers - January 1999 This is considered a Minor repair Model: Sub125 (SCS125 Powered Subwoofer) Subject: Amplifier plate overheating; Blown fuses
In the event you receive a Sub125 (SCS125 Powered Subwoofer) with the complaint amplifier plate is getting too hot, or the unit is blowing fuses, perform the necessary steps listed below to change the bias current of the amplifier. This procedure should be performed on all Sub125 amplifiers being serviced for any reason: 1. Set the subwoofer cabinet on a padded surface with amplifier facing upwards. 2. Remove the (14) Philips screws holding the amplifier and inner plastic cover to the cabinet. Four of these 14 screws are in each corner, slightly larger and just inside the smaller corner screws. 3. Remove amplifier assembly carefully. Do not pull the amplifier out of the cabinet too much; it can disconnect the speaker wires. (The amp assembly can be laid on one corner of the cabinet for the remainder of the procedure without disconnecting the speaker wires). 4. Carefully pry plastic cover off amplifier assembly. If you are too aggressive Molex connector P104 may be damaged; speaker wire inside the cover has little extra length. Lift the left side of the cover first to avoid disconnecting the cable at P104; this connector is located on the right side of the plate inside the cover. 5. Once the cover is pulled back, locate VR101. See Figure 1. 6. Using a thin Phillips screwdriver 5 or more inches long, set trim pot VR101 to Full CCW position (Minimum level). Be gentle to avoid damage to the part. 7. If necessary, replace blown line fuse with h/k part# FS1067, (2A Slo-Blo 5 x 20mm GMC type). 8. Replace the amplifier in the cabinet; replace all (14) screws to secure the amplifier plate and plastic cover.* 9. Functional Test - Set the LEVEL control to minimum (Full CCW). Connect an AC Wattmeter to the AC input line and turn the unit ON; maximum AC measured power should not be more than 12.5 watts. 10. Connect music signal from a CD source and increase volume to a medium level to verify sound from the subwoofer. Do not increase volume to a point where the unit is driven into clipping. No evidence of distortion and/or rattle inside the box should occur. 11. Conduct warm-up for 10 minutes; turn LEVEL control Full CCW or remove signal. Input power as measured by AC Power meter should not exceed 13 watts. If value exceeds this, re-check pot. VR101 position if necessary. 12. Add an adhesive label (dot) to the amplifier plate with the letter a written on it; if the customers outer carton is available, add an a with a marker to the SCS125 printing on the carton in all places where it appears.

Unmodified Sub125 (SCS125 Subwoofer) Factory Modified Sub125a (SCS125 Subwoofer) Orange Label on amplifier plate: This area is designed to become quite warm during normal operation Outer carton marked SCS125 Outer carton marked SCS125a
* Alternately, the amplifier may be driven out of the cabinet by attaching a 4 ohm 25 watt load resistor to the output terminals, and using a 50 Hz sine wave input signal adjusted to achieve 7 volts at the load resistor for the warm-up test.

SCS125/125a PACKING

WARRANTY CARD AI0193

OWNER'S MANUAL AI0360

PLASTIC BAG

WALL HOOK WI0408

FOAM SET WP0344
125SAT SPEAKERS SAT 125 MURAL STAND WI0409
OUTER CARTON SCS125 - WB1782 SCS125a - WB5349
OPTIONAL 125SAT SPEAKER STANDS: FS300

SUB125 EXPLODED VIEW

SUB125/125a PAGE 12 - 1 of 2

Ref. No.

SUB125 Exploded View
PART NUMBER 700KB800 180PBR12C11S 15520001 152U602012 152U602015 150E8604104 150E8604102 180SMS50126 1933M2520 SZ163 725RFA800 725RFB800 FTW6080-311 1742-CJ9030 NOT FOR SALE NOT FOR SALE

#3 #4 #5 #6

#8 #15 #22 #34 #36 #40 #41 #42
DESCRIPTION PLASTIC KNOB POWER SWITCH FUSE HOLDER POWER CORD 120V POWER CORD 230V POWER TRANSFORMER 120V POWER TRANSFORMER 230V SLIDE SWITCH AUTO-ON MICA INSULATOR JBL LOGO RUBBER FOOT (SCS125) RUBBER FOOT (SCS125a) 8" WOOFER SPEAKER TERMINALS AMPLIFIER ASSEMBLY (120V) AMPLIFIER ASSEMBLY (230v)
SUB125/125a PAGE 12 - 2 of 2
SUB125 PCB COMPONENT SIDE

L1 LED101 L3

LED102

PIN_PADSTACK

R149 P104

C107 C102 Q123

Q120 R146

Q108 J127 J128 J129 J130

R111 R107
R116 J123 C109 Q106 R118 BE E

Q109 R131

R148 R150 R117 J115 Q103 VR101 B

B J117 J116 E

R126 C113

R128 R127

PIN_PADSTACK PIN_PADSTACK
R115 Q105 E J132 Q119 C119 R129

J113 J114

Q107 Q302

Q121 P102 J211 R222 IC8

J109 J110

C111 C120 J107 D302

D106 R137

DISC CAPACITOR 4700P 400V +-20% 1

Diodes

D101, 108, 111, 197131N4148 201, 202, 203, 301 D102, 107 D103 D104, 105, 106 D204 D19700KB1405 197131N19915000623 DIODE IN4148 52MM ZENER DIODE 15V 1/2W 52MM BRIDGE DIODE 4A 500V KBL405 DIODE IN4004 ZENER DIODE 3.3V 1/2W 52MM ZENER DIODE 6.2V 1/2W 52MM 1 1
R156 R201, 204, 207 303, 305 R202, 203, 205, 206, 208, 209 R216, 235 R225 R227 R228 R233 R234

Integrated Circuits

IC101, 201, 203, 19006M4558D 204 IC301 190161M311N I.C. OPA 4558D OP-AMP I.C. LM311 COMPARATOR 4 1
R236 R239 R240 R301 R306 R307 R308 VR101 VR201 VR301

Resistors

R101, 102, 104, 11014103J52 146, 210, 211, 212, 217, 226, 237 R103 R105, 126, 128 11014183J52 11014272J52 RESISTOR 10K 1/4W +-5% 10
RESISTOR 18K 1/4W +-5% RESISTOR 2K7 1/4W +-5% RESISTOR 47K 1/4W +-5%
R106, 124, 134, 11014473J52 135, 141, 142,
REF # PART # DESCRIPTION QTY REF # PART # DESCRIPTION

Transistors

Q101, 102, 103, 192027C1815GR 2SC1815GR 110, 112, 113, 114, 116, 117, 122, 123, 201, 202, 301 Q104, 119, 121, 302 Q105 Q106, 118 Q107 Q108 Q109 Q111 Q120 192028A1015GR 2SA1015GR 192028A965Y 192027C2235Y 192022TIP36C 192021TIP35C 192201D882Y 192202B772Y 2SA965R Y 2SC2235Y TIP36C TIP35C KSD882Y KSB772Y 14

Miscellaneous

Q107, 108 LED1 LED1 ***** FS101 FS101 ***** SW101 ***** ***** ***** ***** P201 P102, 3 ***** ***** RY101 JK203 JK201,2 P102/A,103/A, SW201 P201/A P104/A P101 1933M2520 19510204GD 19510204HD 650IH125 FS1067 154U20006T180PBR12C11S 180SMS50126 700KB16210302001 171UGS2121 1740RCB202V 1742CJ9030 1751C02V1B 1751C05V01 1751D02V01 1751D03V01 150E8604104 150E8604102 152U602012 152U602015 MICA ISOLATOR TO-3P 25*20MM LED GREEN 3MM FOR ON LED RED 3MM FOR STANDBY IC HOLDER FUSE 2.0A 120V 5x20mm FUSE 1.0A 230V 20MM UL FUSE HOLDER R3-12 POWER SWITCH PUSH BR12C11S SLIDE SWITCH M50126 PLASTICKNOB 46077-W P.V.C. JUMPER WIRE 52MM TAP CABLE ASSY 2PIN AWG28 80MM CABLE ASSY 2PIN FORLED AWG26 225MM WIRE RED 18AWG 80MM BOTH END TRIPPED AND TINNED RELAYMI-SH-212L OUTLET RCA JACK RCB-202V SPEAKER TEMINAL 6PIN CJ-9030 CONNECTOR 2PIN PITCH=2.5MM CONNECTOR 5PIN PITCH=2.5MM CONNECTOR 2PIN PITCH=3.96MM CONNECTOR 3PIN PITCH=3.96MM POWER TRANSFORMER (120V) POWER TRANSFORMER (230V) POWER CORD (120V) POWER CORD (230V) 2 2

192027C2240GR 2SC2240GR

WIRE ASSY 5PINA ON BOARD 150MM1
SPEAKER WIRE 300MM, #205 0.5T 1 1

1999-03-09

R154 22K R156 10K Q123 C1815 R102 R101 10K 10K C101 MC334

UC00001026

UC00001109

SCS125A PWR-SCH

+VP C108 CD104

UC00001226

UC00001107

R103 18K C102 MC223

UC00001027

7 IC101/B 4558D

R105 2K7 R104 10K

C103 22uF/50V

C104 15P

R115 220

R119 100

UC00001277

UC00001278

R148 3K3 Q119 A1015

R106 47K
R111 3K9 Q103 C1815 RRQ104 A1015 R112 3K9 -15V R114 15K R116 220
Q105 A965 C106 220P R121 R122 330
Q107 TIP36C R146 10K R150 OR22/5W

R149 33K

UC00001035
P201/B PWR_IN STB GND -15V +15V

UC00001214

1N4148

R113 2K2

P103/A D110 RED

R107 3KIC101/A 4558D

R109 4K75 C105 1uF/50V Q101 C1815 Q102 C1815

R145 C130 3K3 CD104

A VR101 500W R108 3K3

SUB125 ONLY

UC00001211 UC00001166 UC00001260
+VP R129 UC00001261 560/1W R126 2K7 C114 CD104 C115 CD104 R128 2K7 C112 22uF/50V R125 3K3

P103/B P102/B D109 GRN

R110 3K82
6K8 R147 R123 OR22/5W 10/1/2W

UC00001279

UC00001168

Q109 D882 R131 15K

2K7/1/2W R137 R151 33K

C116 100uF/16V

C118 6800uF/50V D103 KBL405

-AC +AC

UC00001262

Q106 C2235 R120 100

C107 MC104 Q108 TIP35C C109

P104/A

P102/A

WOOFER

UC00001132
Q121 A1015 R152 12K C121 MC103

P104/B

Q110 C1815 R132 1K8 R133 15K Q111 B772

UC00001265

C120 MC333
R136 1K/2W RY101 OMI-212L D106 1N4004 Q122 C1815

R153 22K P101/A

C117 100uF/16V

D102 VZ15V

C113 22uF/50V R127 3K3 C119 6800uF/50V

UC00001264

FS101 C127 472/400V AC101 2A/250V UC00001274 SW102 POWER P101/B AC120V/60HZ

UC00001266

R130 560/1W

UC00001169

C122 MC103

Q112 C1815

UC00001127

D105 D104 1N4004 1N4004

PT101 2K7/1W R308 C302 100uF/16V R302 51K 3K VR301 D302 VZ6V2 6K8 R6

R141 47K

R142 47K D111 1N4148
R138 33K D107 VZ15V Q117 C1815

910 5K6 R306 R301

R139 33K D108 1N4148 Q116 C1815 Q118 C2235

R134 47K

C123 100uF/50V