JBL PowerBass PB12 User manual

PowerBass
™
Series
PB12
Powered Subwoofer
Service Manual
JBL Consumer Products
250 Crossways Park Dr.
Woodbury, New York 11797 Rev10 2/2004

PB12 TABLE OF CONTENTS
Safety Information ………………………………………………….……….3
Basic Specifications ……………………………..………………………….4
Detailed Specifications ……………………………………….…………….5
Controls and their Function………….……..……………………………….6
Connections …………………….……………………………………………7
Operation ……………………………………………………………………10
Troubleshooting…………………………………………….……………….11
Test Setup and Procedure …………………………………………..…….12
Service Bulletin JBL 2001-03 ……………………….…………………….13
Service Bulletin JBL 2001-04 …………………………………….……….14
Service Bulletin JBL 2001-05 ……………………………….…………….17
Service Bulletin JBL 2001-07 ……………………………….…………….18
Service Bulletin JBL 2001-08 ……………………………….…………….19
Tech Tip JBLTT2003-04…………………………………..……………….20
Exploded View/Packaging.……………………………………………..….21
Amplifier Exploded View ………………………………………….……….22
Amplifier Faceplate/Access…………………………………………..……23
Integrated Circuit Diagrams……………………………………………….24
Testing Procedures..…………… …………………………………………26
Block Diagram Revision 2…………………………………………………32
Electrical Parts List (PCB version 6.3 – 7.0)…………………………… 33
Electrical Parts List (PCB version 7.2) ……………………………..……37
Electrical Parts List Revision 2…………………………………………….41
Printed Circuit Boards (PCB version 6.3)…………………...……..…….44
Printed Circuit Boards (PCB version 6.4)………..…..……………….….47
Printed Circuit Boards (PCB version 7.2)… …………………………….48
Schematics Version 1
Preamp (PCB version 6.3)…………………………… …….……….51
Power Amp (PCB version 6.0 -6.3)…….. ………………………….52
Power Amp (PCB version 7.0)…………… …………………..…….53
Preamp (PCB version 7.2)…………………………… ……….…….54
Power Amp (PCB version 7.2)……………………………. …… ….55
Schematics Version 2……………………………………………..…….…56
PB12 – DIFFERENCES IN REVISION 1 AND REVISION 2
REVISION 1 REVISION 2
Amplifier faceplate says “Made in Canada”
Amplifier serial number starts with “AM”
Black (or silver) potted, non-serviceable output module
Amplifier serial number starts with “HA”
Output transistors in the open, on a large black heatsink
Large plastic cup enclosing the rear of the amp assembly
Main PCB, bottom, solder-side contains all SMD devices
“Made in Mexico” label on outer part of cabinet
BOTH VERSIONS OF THESE AMPLIFIERS ARE NOT CONSIDERED INTERCHANGEABLE; THEY ARE
NOT A DROP-IN REPLACEMENT IN THE CABINET OF THE OTHER VERSION.

PB12
3
Warning
Any person performing service of this unit will be exposed
to hazardous voltages and the risk of electric shock. It is
assumed that any person who removes the amplifier from
this cabinet has been properly trained in protecting
against avoidable injury and shock. Therefore, any service
procedures are to be performed by qualified service
personal ONLY!
Caution
Before the amplifier is plugged in, be sure its rated
voltage corresponds to the voltage of the AC power
source to be used. Incorrect voltage could cause damage
to the amplifier when the AC power cord is plugged in. Do
not exceed rated voltage by more than 10%: operation
below 90% of rated voltage will cause poor performance
or may shut the unit off.
Leakage/Resistance Check
Before returning the unit to the customer, perform a
leakage or resistance test as follows:
Leakage Current. Connect the unit to its rated power
source. Using an ammeter, measure the current between
the neutral side of the AC supply and chassis ground of
the unit under test. If leakage current exceeds 0.5mA, the
unit is defective. Reverse the polarity of the AC supply
and repeat.
Resistance. Measure the resistance from either side of the
line cord to chassis ground, If it is less than 500k ohms,
the unit is defective.
WARNING! DO NOT return the unit to the customer if it
fails one of these tests until the problem is located and
corrected.
Critical Components
All components identified with the IEC
symbol in the parts list and schematic
diagram designate components in which
safety can be of special significance when
replacing a component identified with. Use
only the replacement parts designated in the parts list or
parts with the same rating of resistance, wattage or voltage.
SAFETY INFORMATION
List of Safety Components
Requiring Exact Replacements
Revision 1 Revision 2 Description
F1 - 80117 093-105202-300 Line Fuse Slo Blo 2.0A
PWRCORD 083-041802-009 250V UL approved
80105 SPT-2 or better with
polarized plug, UL
approved wired with the
hot side to fused side.
Use with factory
replacement panel strain
relief (70305) only.
TRX 042-010053-003 Power Transformer. Use
80116 only factory replacement.
BR RECT BR1 Bridge diode. Use only
50100 052-400080-000 factory replacement.
C1,2 C6,8 Large electrolytic filter
(2200uF 100V) (3300uf 80v) caps. Be sure
30710 034-470745-200 replacement part is at
least the same working
voltage and capacitance
rating.
Also the lead spacing is
important. Incorrect
spacing may cause
premature failure due to
internal cabinet pressure
and vibration.
C10 Does not apply 4.7uF, 100 volt NPE low
30718 df radial.
(On Power amp PCB)
S64AMI Does not apply Power output module.
60302 Use only factory
replacement
Faceplate n/a Use only factory
70325 replacement
Rear Amp Cover 063-531808-000 Use only factory
Does not apply replacement
Inductor Does not apply CMC - Use only factory
80100 replacement
Inductor Does not apply L1 - Use only factory
80121 replacement
Does not apply Inductor L2 - Use only factory
043-300101-000 replacement
Does not apply Inductor L3 - Use only factory
043-700101-000 replacement

PB12
4
Output Power 250 watts RMS
Driver 12" Woofer
Frequency Response 25Hz – Low-Pass Frequency setting
Inputs Line Level (option: LFE); Speaker Level
Outputs Speaker level fixed frequency 150Hz
Low-Pass Frequency Variable from 50Hz – 150Hz
High-Pass Frequency 150Hz when using Speaker Level Output
Dimensions (H x W x D) 15 1/2" x 15" x 16"
394mm x 381mm x 406mm
(with feet) 17 1/2" x 15" x 16"
445mm x 381mm x 406mm
Weight 40 lb/18.2kg
Refinements may be made on occasion to existing products without notice but will always meet or exceed original
specifications unless otherwise stated.
PowerBass is a re
g
istered trademark of JBL, Incorporated.
00261-1
BASIC SPECIFICATIONS PB12 Subwoofer

PB12
5
JBL PB12 250W Powered Sub Amp
LINE VOLTAGE Yes/No Hi/Lo Line Nom. Unit Notes
US 120vac/60Hz Yes 108-132 120 Vrms Normal Operation
EU 230vac/50-60Hz Yes 207-264 230 Vrms Normal operation, MOMS required
Parameter Specification Unit QA Test
Li
m
i
ts
Conditions Notes
Amp Section
Type (Class AB, D, other) D n/a n/a
Load Impedance (speaker) 5.6 Ohms n/a Nominal
Rated Output Power (120VAC) 250 Watts 140 Domestic version onl
y
120 VAC-60 Hz
Rated Output Power (230VAC) 250 Watts 130 EU Version onl
y
230 VAC-50 Hz
THD @ Rated Power 0.3 % 122k filter 145 Watts
THD @ 1 Watt 0.1 % 0.5 22k filter
DC Offset 10 mV-DC 20
@
S
p
eaker Out
p
uts
Damping factor >50 DF 35 Measured at amplifier board At spkr cable. 150 Watts @ THD < 0.1 % @ 50 Hz
Input Sensitivity
Input Frequency 50 Hz 50 Nominal Fre
q
.
L&R 240 mVrms ±2dB To 150 Watts Sin
g
le in
p
ut driven
LFE input 240 mVrms ±2dB To 150 Watts Sin
g
le in
p
ut driven, LFE switch ON
Speaker/Hi Level Input 2.4 Vrms ±2dB To 150 Watts Sin
g
le in
p
ut driven
Signal to Noise
SNR-A-Weighted 90 dBA 70 relative to rated
p
ower A-Wei
g
htin
g
filter
SNR-unweighted 85 dBr 70 relative to rated
p
ower 22k filter
SNR rel. 1W-unweighted 65 dBr 60 relative to 1W Out
p
ut 22k filter
Residual Noise Floor 1 mVrms 3 Volume @max, using RMS reading
DMM/VOM (or A/P) BW=20 Khz.
Line level inputs must be terminated using 1KOHM
Residual Noise Floor 1.5 mVrms(max) 3 Volume @max, w/ A/P Swept
Bandpass Measurement (Line freq.+
harmonics) (BW
=
20 Khz)
Line level inputs must be terminated using 1KOHM
Input Impedance
Line Input (L, R,LFE) 20K ohms n/a Nominal
Speaker/Hi Level Input 4.7K ohms n/a Nominal
Filters
LP filter 4th order fixed 60-180 Hz ± 10 2nd order variable + 2nd order fix-24 db/Octave
Subsonic filter (HPF) 3rd Order Fixed
LFE Low pass 2nd order 200>LP<1K Hz LFE in
p
ut driven onl
y
HP speaker out connector 200 Hz ± 10 S
p
eaker in
p
ut driven - 4 Ohms
100 Hz ± 10 S
p
eaker in
p
ut driven - 8 Ohms
Features --
Volume pot Taper (lin/log) LOG -- functional A Ta
p
er
HP Speaker out YES functional Refer to Filter section
Phase switch 0-180 deg functional
LP Filter defeat switch YES functional Disables LP filter, intended for LFE
Input Configuration
Line In (L,R) & LFE YES -- functional Dual RCA jack
Spkr/Hi Level In YES -- functional Bindin
g
p
ost connector L&R
Signal Sensing (ATO)
Auto-Turn-On (yes/no) YES functional
ATO Input test frequency 50 Hz functional "
ATO Level LFE Input 4 mV functional " Maximum acce
p
table level.
ATO Level Speaker in 50 mV functional " Maximum acce
p
table level.
ATO Turn-on time 5 ms functional Amp connected and AC on, then input
s
i
gna
l
app
li
ed
Auto Mute/ Turn-OFF Time 15 minutes 15 T before muting, after signal is
r
emo
v
ed
Auto turn of time (T) must be 5 > T < 15 Minutes
Power on Delay time 3 sec. 4AC Power A
pp
lied
Transients/Pops
ATO Transient 5 mV-peak n/a
@
S
p
eaker Out
p
uts
Turn-on Transient 50 mV-peak 2v-
pp @
S
p
eaker Out
p
uts AC Line c
y
cled from OFF to ON
Turn-off Transient 50 mV-peak 2v-
pp @
S
p
eaker Out
p
uts AC Line c
y
cled from ON to OFF
Efficiency 65 % 64 Nominal Line volta
g
e 120 VAC
Stand-by Input Power 24 Watts 26 @ nom. line voltage Maximum allowable input power under nominal
Input voltage and frequency, HOT or COLD
operation.
Power Cons. @ rated power 234 Watts 240
@
nom. line volta
g
e 150 Watts
@
5.6 Ohms nominal line volta
g
e
Protection
Short Circuit Protection YES functional Direct short at output Amplifier should resume operation after short circuit
cond
i
t
i
on
r
emo
v
a
l
Thermal Protection YES functional @1/8 max unclipped Power at 1.06
t
i
mes
the
i
nput
v
o
l
tage
DC Offset Protection YES -DC
p
resent at S
p
eaker Out leads
Line Fuse Rating
USA-Domestic 2 Amps Type-T or Slo Blo-250 V
EU 1.25 Am
p
sT
yp
e-T or Slo Blo-250 V External fuse with UL/SEMKO rated holder
DETAILED SPECIFICATIONS PB12 Subwoofer

PB12
6
PB12 Subwoofer Controls and Their Function
1. Power - These lights will be red when the unit is
plugged in and not receiving a signal; when the PB12
receives a signal, the lights will cycle to GREEN. If no
signal is received after 10-15 minutes the lights will
cycle back to RED (standby) until a signal is present
again.
2. Level Control - The subwoofer Level Control, PB12,
(located on the rear panel) adjusts the volume of the
subwoofer relative to the rest of the system.
3. LFE/Normal Switch - Ordinarily placed in the Normal
position - but switch to LFE when playing Dolby®
Digital, DTS®or other digital surround modes - see
page 9.
4. Phase Switch - Changes the subwoofer’s output to
be in phase or 180 degrees out of phase with the
program material.
5. Crossover Frequency - Sets the highest frequency
the subwoofer will reproduce.
6. Line Input - Main Input connection to subwoofer
(preferred).
7. Speaker In Jacks - Main Input connection to
subwoofer when line level, subwoofer, or pre-amp
output connectors are not available, or when a high
pass filter (set at 150Hz) to main loudspeakers is
desired through the Speaker Output Jacks.
8. Speaker Out Jacks - Connected to main
loudspeakers when the Speaker Input Jacks are used.
9. Power Switch - Turns the PB12 on or off.
Rear Panel
Front Panel
R

PB12
7
Speaker Connection
When we designed the PB12
powered subwoofers, our goal
was to offer the user the best
possible performance
combined with the most
flexible and complete
installation options. Please
look over the following three
examples to determine which
description best matches
your system and follow the
corresponding hookup
instructions.
To use the binding-post
speaker terminals with bare
wire, unscrew the collar until
the hole through the center-
post is visible under the collar.
Insert the bare end of the wire
through the hole in the post,
then screw the collar back
down until the connection is
tight. The holes in the center
of the collars are intended for
banana-type connectors.
Dolby Pro Logic (Non-Digital) – Speaker Level
Use this installation method for
Dolby Pro Logic applications
(not Dolby Digital, DTS or other
digital processing), where the
receiver/processor does not
have a subwoofer output or a
volume-controlled preamp
(line-) level output:
Connect your receiver or
amplifier’s front left and right
speaker terminals to the left
and right terminals on the
subwoofer that are marked
“High Level In.” Connect the
left and right terminals on the
subwoofer that are marked
“High Level Out” to the
corresponding terminals on
the back of your front left
and right speakers.
Connect your receiver or
amplifier’s center, left and right
surround-speaker terminals to
the corresponding terminals on
the back of your center, left
and right surround speakers.

PB12
8
Dolby Pro Logic (Non-Digital) – Line Level
Use this installation method for
Dolby Pro Logic applications
(not Dolby Digital, DTS or other
digital processing), where the
receiver/processor is equipped
with a subwoofer output or a
volume-controlled preamp
(line-) level output:
Use RCA-type patch cords
to connect the line-level
subwoofer outputs on your
receiver or amplifier to the line-
level inputs on the subwoofer.
IMPORTANT: Make sure that
the LFE toggle switch on the
subwoofer is in the “Normal”
position. Do not use the “LFE”
position with Dolby Pro Logic-
only processors.
Note: If your receiver or
amplifier only has one
subwoofer output jack,
then you may connect the
subwoofer output on your
receiver/preamplifier to either
the left or right line-level input
on the subwoofer. It makes no
difference which jack you
choose.
Connect each speaker to
the corresponding speaker
terminals on your receiver or
amplifier.
Make sure your receiver or
processor is configured
cor
rectly: Make sure that the
sub
woofer is configured as
“On.”
Note for advanced users: If
your receiver/processor has
a built-in low-pass crossover
filter for the subwoofer output,
then the LFE switch should be
set to the “LFE” position to
bypass the subwoofer’s
internal crossover.

PB12
9
Dolby Digital or DTS (or Other Digital Surround Mode) Connection
Use this installation method for
Dolby Digital, DTS or other
digital surround processors:
IMPORTANT: Make sure that
the LFE toggle switch on the
subwoofer is in the “LFE”
position. Use the line-level
input jacks for the Low-
Frequency Effects channel.
Connect these jacks to the LFE
output or subwoofer output on
your receiver or amplifier.
Note: If your receiver or
amplifier only has one
subwoofer output jack,
then you may connect the
subwoofer output on your
receiver/preamplifier to either
the left or right line-level input
on the subwoofer. It makes no
difference which jack you
choose.
Connect each speaker to
the corresponding speaker
terminals on your receiver
or amplifier.
Make sure that you have
configured your surround-
sound processor for
“Subwoofer On” or “LFE On.”
The front left, front right, center
and rear speakers should be
set to “Small” or “Large”
depending on their size and
frequency response. Consult
your receiver’s or processor’s
owner’s manual.

PB12
10
OPERATION
Power
When the unit is plugged in
and the power switch is on and
no signal is received, the LEDs
on the front of the unit will turn
red. When a signal is present,
the LEDs will turn green.
Note: It will take several
minutes for the LEDs to turn
from green to red after the
input signal to the subwoofer is
removed. Due to JBL’s unique,
high-output,
high-efficiency
amplifier design, power
consumption is minimal when
the subwoofer is not receiving
a signal.
PowerBass PB12
CAUTION
RISK OF ELECTRIC SHOCK
DO NOT OPEN
120V
60Hz
CROSSOVER
FREQUENCY
LEVEL
LINE LEVEL IN
PHASE
Min Max
L
R
L R
For LFE use L or R
LFE NORMAL
PowerBass PB12
HIGH
LEVEL
IN
L
R
HIGH
LEVEL
OUT
+ –
50Hz
0º 180º
150Hz
POWER
ON OFF
The subwoofer Level Control
adjusts the volume of the
subwoofer relative to the rest
of the system. Proper level
adjustments depend on several
variables such as room size,
subwoofer placement, type of
main speakers and listener
position. Adjust the subwoofer
level so that the volume of the
bass information is pleasing
to you.
Level Control
Crossover Adjustments
The Crossover Frequency
Control determines the highest
frequency at
which the
subwoofer reproduces
sounds.
If your main speakers can
comfortably reproduce some
low-frequency sounds, set this
control to a lower frequency
setting, between 50Hz – 100Hz.
This will concentrate the
subwoofer’s efforts on the
ultradeep bass sounds required
by today’s films and music. If
you are using smaller bookshelf
speakers that do not extend to
the lower bass frequencies, set
the low-pass crossover control
to a higher setting, between
120Hz – 150Hz. This control is
not used when the LFE switch
is in the “LFE” position.