JBL SUB-125, SUB-125-A Service manual
SUB125/125a
Amplifier/Subwoofer
SERVICE MANUAL
JBL Consumer Products Inc.
250 Crossways Park Drive
Woodbury, N.Y. 11797
A Harman International Company
Rev B 7/2003
Amplifier/Subwoofer 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
GENERAL SPECIFICATIONS
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
SCS125/125a System
Frequency Response
35Hz – 20kHz (–6dB)
SUB125
Amplifier . . 75 watts RMS
Bass .....8"woofer, bass-reflex enclosure
Dimensions (HxWxD)
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.
2
Amplifier/Subwoofer SUB125
SCS125/125a SPECIFICATIONS
LINE VOLTAGE Yes/No
US 120vac/60Hz Yes 108-132 Vrms Normal Operation
EU 230vac/50-60Hz Yes 207-264 Vrms Normal operation, MOMS
Asia 100vac/50Hz Yes 90-110 Vrms Normal Operation
Spec. Unit Limits Conditions Notes
Amp Section
Type (Class AB, D, other) AB AB n/a Sink required for Class AB
Load Impedance (speaker) 4 Ohms n/a Nominal Z-curve required
Rated Output Power 80 Watts 80 1 input driven
THD@ Rated Power 0.08 % 0.3 22k filter
THD @ 1 Watt 0.1 % 0.5 22k filter
DC Offset 10 mV-DC 20 @ Speaker Outputs
Damping factor <200 DF n/a
Input Sensitivity
Input Frequency 50 Hz 50 Nominal Freq. 1 input driven
Line Input 220 mVrms ±2dB To Rated Power 1 input driven
Speaker/Hi Level Input 4.26 Vrms ±2dB To Rated Power (-26dB below Line In)...1
Hi/Lo Line Unit Notes
required
input driven
Signal to Noise
SNR-A-Weighted 100 dBA 90 rel. to rated power A-Weighting filter
SNR-unweighted 80 dBr 60 rel. to rated power 22k filter
SNR @ 1W-unweighted 60 dBr 55 rel. to 1W Output 22k filter
Residual Noise Floor 1.5 mVrms 2.5 Volume @max, using RMS reading DMM/VOM (or A/P)
Residual Noise Floor 1 mVrms(max) 2 Volume @max, w/ A/P Swept Bandpass Measurement
Input Impedance
Line Input 15K ohms n/a Nominal
Speaker/Hi Level Input 4.7K ohms n/a Nominal
Filters
Low Pass (fixed or
variable)
Low Pass filter (point or
range)
Slope 24 dB/Octave n/a
Q 1.8 Damping n/a 2 cascaded 2nd order
Subsonic filter (HPF) 31 Hz ±2dB -3dB Point
Slope 12 dB/Octave n/a
Q 1.4 Damping n/a
fixed — —
135 Hz ±2dB -3dB Point
(Line freq.+ harmonics)
filters of 1.8 &0.7 Q
3
Amplifier/Subwoofer SUB125
Signal Sensing (ATO)
Auto-Turn-On (yes/no) yes — functional
ATO Input Frequency 50 Hz functional
ATO Level 2 mV functional 2mV@50Hz into Line Input
ATO Bandwidth 5k Hz functional ATO-LPF for noise
ATO Turn-on time 5 ms functional Amp connected and AC on, then input signal applied
Auto Mute/ Turn-OFF Time 20 minutes functional T before muting, after
w/ 1 ch. driven
immunity
signal is removed
DV1 measured 7mV @
5kHz…. 2mV @ 1kHz
Power on Delay time
Transients/Pops
ATO Transient 5 mV-peak 10 @ Speaker Outputs
Turn-on Transient 50 mV-peak 100 @ Speaker Outputs AC Line cycled from OFF to
Turn-off Transient 50 mV-peak 100 @ Speaker Outputs AC Line cycled from ON to
Efficiency
Stand-by Input Power 10 Watts n/a @ nom. line voltage
Power Cons.@rated power 160 Watts n/a @ nom. line voltage
Protection
Short Circuit Protection Yes — functional Direct short at output
Thermal Protection 65 deg.C— functional @1/8 max unclipped
DC Offset Protection yes — functional DC present at Speaker
Line Fuse Rating 2 Amps 2 Type-T or Slo Blo External fuse with UL/SEMKO
3 sec. functional AC Power Applied
Power
Out leads
ON
OFF
DV1:Plate=50deg.C
max.Tab=90deg.C max.T-on
=65deg.C
Relay or crowbar (for
driver/fire protection)
rated holder
4
Amplifier/Subwoofer SUB125
CONTROLS AND THEIR FUNCTION
1234
SPEAKER LEVEL OUTPUT SPEAKER LEVEL INPUT
CC
LL
RR
SUB125
ON AUTO
LINE LEVEL
L
R
STAND BY ON
FUSE
2A/250V
INPUT
SUBWOOFER
MIN
POWER
FUSE
LEVEL
AC 120V ,60Hz
MAX
160W
5
6
7
8
~
9
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
5
Amplifier/Subwoofer SUB125
SCS125/125a SPEAKER LEVEL CONNECTIONS
Left Front
LL
Right Front
Center
SUB125
SPEAKER LEVEL OUTPUTSPEAKER LEVEL INPUT
CC
RR
Receiver
Left Front
Left Surround
Center
Right Front
Right Surround
Left Surround Right Surround
6
Amplifier/Subwoofer SUB125
SCS125/125a LINE LEVEL CONNECTIONS
Center
Left Front
Left Front
SUB125
LINE LEVEL
INPUT
L
R
Receiver
Subwoofer
Out
Right Front
Right Front
L
R
Left Surround
Center
Right Surround
Left Surround Right Surround
7
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