JBL BASS20 User manual

SERVICE MANUALSERVICE MANUAL
Powered Subwoofer
JBL Consumer Products Inc.
80 Crossways Park West
Woodbury, N.Y. 11797
1-800-336-4JBL in the USA
A Harman International Company
Part No.: 1112-JBLBASS20
BASS20

1
Powered Subwoofer BASS20
TABLE OF CONTENTS
Specifications .................................................................1
Features..........................................................................1
Powered Sub Test Setup...............................................2
Test Procedure...............................................................3
Important Service Note ..................................................4
Block Diagram ................................................................5
Amplifier Exploded View ................................................6
Cabinet Assembly Exploded View.................................7
Parts Lists.......................................................................8
Packaging View............................................................10
Printed Circuit Boards .................................................11
Integrated Circuit Diagram ...........................................13
Schematic Diagrams ...................................................14
SPECIFICATIONS
Amplifier Power (RMS) .......150Watts
Low Frequency Woofer (2) ......81/2"
Design.............Bass reflex enclosure, Grey or White
Inputs .............Line Level and Speaker Level
Outputs ............Full Range Speaker
Crossover Frequency ........120Hz
Frequency Response ........40Hz - 120Hz (+/-3dB)
External Dimensions (Inches)
Height .............17-3/4"
Width .............10"
Depth .............24"
External Dimensions (mms)
Height .............451
Width .............254
Depth .............610
Weight.............42lbs (19.1kg)
FEATURES
nThe Bass20 powered subwoofer is part of the SCS120 or
MUSIC 20 System.
n150 watt output.
nVariable level control.
nLine level or Speaker level inputs, outputs for full range
satellite speakers.
nUser friendly auto on circuit. Signal sensing
automatically turns the subwoofer on so you don’t have
to; the subwoofer is meant to be left on without
continual use of the power switch.

2
Powered Subwoofer BASS20
BASS 20 POWERED SUB WOOFER TEST SETUP
JBL continually strives to improve its products. New materials, production methods and design refinements are introduced into
existing models without notice as a routine expression of our design philosophy. For this reason, Bass Series loudspeakers
may differ in some respect from their published specifications and descriptions, but will always equal or exceed the original
specifications unless otherwise stated.

3
Powered Subwoofer BASS20
TEST PROCEDURE
Equipment Needed:
nFunction generator/signal generator/sweep generator
nIntegrated Amplifier
nMultimeter
nCables - Line level (RCA) and Speaker cables
UUT = Unit Under Test
General Function
1. Connect both left and right line level inputs (RCA) to signal generator and UUT. Use Y-cable if necessary
from mono source.
2. Turn on generator and adjust to 100mV, 50 Hz.
3. Plug in UUT; red LED should be ON. Turn power switch to the ON or AUTO position and turn LEVEL control
full clockwise.
4. Green LED should light, immediate bass response should be heard and felt from port tube openings.
5. Turn off generator, turn unit to OFF, disconnect RCA cables.
6. Connect two pairs of speaker cables to high level input terminal on UUT. Cables should be connected to an
integrated amplifier fed by the signal generator. Observe polarity of speaker cables.
7. Turn on generator and adjust so that speaker level output is 2.5V, 50 Hz.
8. Turn power switch to the ON or AUTO position and turn LEVEL control full clockwise.
9. Green LED should light, immediate bass response should be heard and felt from port tube opening.
Sweep Function
1. Follow steps 1-4 above, using a sweep generator as a signal source.
2. Sweep generator from 20Hz to 300Hz. Listen to the cabinet and drivers for any rattles, clicks, buzzes or any
other noises. If any noises are heard, remove driver and test.
Driver Function
1. Remove one or both drivers from cabinet; remove + and - wire clips.
2. Check DC resistance of driver; it should be 4.2 ohms.
3. 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.
SERVICE NOTE (120v Version only)
Even though the Bass20 seems to have an on/off power switch, in fact the switch does not
switch the main power off to the amp assembly, even in the OFF position. All AC and DC
voltages within the amplifier are still active, so for safety concerns the AC power cord should
be unplugged before any servicing begins.

4
Powered Subwoofer BASS20
Amplifier assemblies with serial numbers less than 11757 should be modified for safe operation. Examine amplifier
as follows (serial #11756 or lower) to determine if a factory modification has taken place:
1. Unplug and remove amp assembly; (12) #8 x 3/4" screws.
2. Lift and examine the main (large) amp board, solder (green) side of the board.
3. Look for the presence of two large resistors (1k, 3 Watt or 470 ohm, 1Watt) directly underneath the two large
filter caps on the opposite side of the board.
4. If these resistors are present, the unit has been modified.
5. If they are missing, the unit should be modified before future use, regardless of what the initial service concern
was. To continue without modification may result in a hazardous condition.
MODIFICATION:
1. Cut tie wraps to bundled wire assemblies for easier access. Circuit board does not have to be removed from
heatsink.
2. R36: See drawing: cut trace connecting Q4 collector and main C1 (+) pad.
3. Create solderable surface on PCB, (on Q4 side of cut) by scraping the green mask from board with Exacto
knife or similar tool.
4. Attach R36, 470Ω1W resistor (JBL #RS2180) to new surface and cathode side of CR1. Resistor should
"stand off" from PCB; secure with RTV or epoxy if desired.
5. R41: See drawing; cut trace connecting Q1 collector and main C2 (-) pad.
6. Create solderable surface on PCB, (just above R49) by scaping the green mask from the board with Exacto
knife or similar tool.
7. Attach R41, 470W 1W resistor (JBL #RS2180) to new surface and C1 (-) pad. Resistor should "stand off" from
PCB; secure with RTV or epoxy if desired.
8. Retie cables with tie wraps.
9. Cut and insert two in-line fuse holders (JBL #155020A) with 4A fuses (JBL #312004); one in each positive wire
leading to woofer terminal, close to the amplifier assembly.
10. Replace amp assembly in cabinet.
IMPORTANT SERVICE NOTE:

5
Powered Subwoofer BASS20
BASS 20 (120v US & 230v European Versions) BLOCK DIAGRAM

6
Powered Subwoofer BASS20
BASS20 (120V & 230V versions) AMPLIFIER EXPLODED VIEW

7
Powered Subwoofer BASS20
BASS20 CABINET ASSEMBLY EXPLODED VIEW

8
Powered Subwoofer BASS20
MECHANICAL PARTS LIST
REF. NO. PART NO. DESCRIPTION QTY
1 BR1187 ALUM. BAR 4.8mmx12.7mmx40m 2
BR1387 ALUMINUM BAR 1.9"x0.5"x0.1 1
2 HS1102 HEAT SINK ASSY. 1
3 FH1002 FUSE HOLDER 1/4x1-1/4 (120V) 1
FH1003 FUSE HOLDER 5x20mm (230V) 1
4 SEE FUSES
5 LB1269 LABEL FOR HEATSINK (120V) 1
LB1298 LABLE FOR HEATSINK (230V) 1
7 MS1004 SILICONE GREASE #340 DOW
8 PM1366 GASKET FOR BASS20 1
9 TE1125 TERMINAL ULTRA FAST INS. 9
10 WI1637 WIRE #18 BLUE/WHITE TRACER 3"
11 SC1192 Sc 6-32x7/8 TAPT-THR HEX W 2
12 WA1049 WASHER EXT. TOOTH #6 ZINC 6
13 XX1250 STRAIN RELIEF SPT-1 BLACK 1
15 SC1215 SCREW M3x1.25x10 plas-Thr Pan 5
17 XX1174 AC CORD. 6FT UL/CSA APRO. (120V)1
WI1597 AC CORD. 6FT UL/CSA APRO. (230V)1
18 SP1020 SIL. FOAM 3/8"Lx1/4"Wx3/16 2
19 SP1073 SIL PAD TO-3P 1.0"x0.75" 4
20 XX1257 COVER PLASTIC 1
21 XX1259 KNOB BLACK CUSTOM 1
22 WA1032 WASHER PLAIN #6 ZINC FINISH 4
23 SC1194 Sc 6-32x3/8 TAPT-THR HEX 4
331364-001 GASKET 1
61868 Sc #8x3/4" Blk Pan Head Phillips 12
305718-001 FOOT 4
63868 INSERT THREADED (for foot)
332246-001 SUBWOOFER 2
900101-016 SCREW #8x1" Blk Pan Head 8
C01076 RCA JACK DUAL GOLD RED/WHT 1
C01256 JACK SPEAKER QUAD PC 2
CT, LINE 1 TE1175 TRMNL MALE TAB 0.32"x0.25" PI 3
LINE 2
ELECTRICAL PARTS LIST
Capacitors
C1, C2 CP1635 CAP ALUM EL 4700uF 20% 63v 2
C3, 20 CP1473 CAP CERAMIC 220 pF 50V P 2
C4, 24, 30 CP1415 CAP ALUM EL. 2.2uF 20% 50V P 6
31, 32, 33
C5 CP1439 SMD CAP 33nF 10% 100V X7R PI 1
C7 CP1633 CAP CERAMIC 0.033uF 5% 50 PI 1
C8, 10, 13 CP1552 SMD CAP 0.1uF 20% 100V Z5U P 3
C9, 12, 27, 29 CP1417 CAP ALUM EL. 22uF 20% 16V P 4
C11 CP1178 CAP POLY FILM 22nF 5% 63V P 1
REF. NO. PART NO. DESCRIPTION QTY
C14, 16 CP1426 SMD CAP 0.1uF 20% 50V Z5U P 2
C15 CP1479 SMD CAP 3300pF 10% 100V X PI 1
C19, 28 CP1645 CAP AL EL 22uF 20% 63V 85 PI 2
C21 CP1478 SMD CAP 330pF 5% 100V NPO P 1
C22 CP1475 SMD CAP 33pF 5% 50V NPO 12 P 1
C23 CP1411 CAP ALUM EL. 100uF 20% 16V P 1
C1P CP1426 SMD CAP 0.1uF 20% 50V Z5U P 1
C2P, C3P CP1480 SMD CAP 470pF 5% 100V NPO 2
C4P CP1552 SMD CAP 0.1uF 20% 100V Z5U P 1
C5P, 6, 17 CP1579 33µF 16V NPE 3
CX CP1808 0.1µF 250V 1
CX1, CX2, CP1844 0.01µF 200V SMD 4
CX3, CX4
Diodes
CR1, 2, 3, 4 DI1005 1N5401 DIODE 3A/200V P 4
D1, 2, 3, 4, 5 DI1132 SMD DIODE 1N4148 LL-34 PKG T P 5
Z1, 2 DI1150 SMD ZENER 15V 5% CP PKG T P 2
Fuses
F1 (120V) 870-0052 FUSE Fast Blow 5A 250V 3AG 1
F1 (230V) 870-0017 FUSE Fast Blow 2A 250V 3AG 1
F2 FS1073 FAST BLOW 8A 250V ACG 1
(early versions)
F2 312004 FAST BLOW 4A 250V ACG 2
(later versions)
Integrated Circuits
IC1, 2, 3, IC1041 IC SMD DUAL J-FET NJM072B 5
4, 5 OP AMP
Resistors
J1, 2, 3, 4, 5, RS1779 SMD RES ZERO ΩJUMPER 12 P 8
6, 7, 10
P1 RS1794 POT, 50KΩ20% LOG TAPER 1
R1, 2, 4, 5, RS1702 SMD RES 100KΩ5% 1/8W 12 P 8
24, 42,
57, 58
R3, 8, 14, 18 RS1701 SMD RES 10KΩ5% 1/8W 120 P 15
21, 23, 27,
32, 38, 39,
45, 50, 52,
53, 54
R6, 7, 31, 48 RS1700 SMD RES 1KΩ5% 1/8W 12 P 4
R9, 10 RS1720 SMD RES 200KΩ1% 1/8W 1 PI 2
R11 RS1872 SMD RES 51KΩ5% 1/8W 120 P 1
R12 RS2101 SMD RES 24KΩ5% 1/8W 120 PI 1
R13, 15 RS1704 SMD RES 22KΩ5% 1/8W 120 P 2
R16, 49 RS1715 SMD RES 5.6KΩ5% 1/8W 1 P 2
R17 RS1883 SMD RES 1.5KΩ5% 1/8W 12 P 1
R19 RS1878 SMD RES 10Ω5% 1/8W 120 P 1
R20, 40 RS1829 SMD RES 160Ω5% 1/8W 12 P 2
R22, 33, 34 RS1705 SMD RES 4.7KΩ5% 1/8W 12 P 3
R25 RS1831 SMD RES 7.5KΩ5% 1/8W T/ P 1
BASS 20 PARTS LIST

9
Powered Subwoofer BASS20
REF. NO. PART NO. DESCRIPTION QTY
R26, 28 RS1717 SMD RES 100Ω5% 1/8W 12 P 2
R29 RS1716 SMD RES 33.2K 1% 1/8W 120 P 1
R30 RS1711 SMD RES 220Ω5% 1/8W 12 P 1
R35 RS1912 SMD RES 11KΩ5% 1/8W 120 P 1
R36, 41 RS2180 470W 1W (early versions: 1K 1W) 2
R37 RS1703 SMD RES 2.2KΩ5% 1/8W 12 P 1
R43, 44 RS1968 SMD RES 2.2MΩ5% 1/8W 12 P 2
R47, 55 RS1767 SMD RES 1 MΩ5% 1/8W 120 P 2
R51 RS1793 SMD RES 475K 1% 1/8W 12 P 1
R56 RS1722 SMD RES 470Ω5% 1/8W 12 P 1
R1P, 1AP, 2P RS1868 RES. W/W 0.1Ω5% 5W RAD P 4
2AP
R3P, R7P RS1994 RES. 100Ω, 5%, 1/4W, C/F, T/R 2
R5P, R6P RS1916 RES. C/F 5.1Ω5% 1/4W T/ P 2
Transistors
Q1 TR1135 TRANSISTOR PNP 2N5401 1
Q2 TR1108 TRANSISTOR 2SC2412 SMD NPN 1
Q4 TR1134 TRANSISTOR 2N5551 NPN 1
Q5 TR1167 TRANSISTOR 2N5551 NPN 1
Q6 TR1131 TRANSISTOR DTC114TK SMD NPN 1
Q7 TR1063 TRANSISTOR MPS2222A NPN 1
Q8 TR1166 TRANSISTOR PNP 2N5401 1
Q1P, Q1AP TR1245 TRANSISTOR NPN TIP35E 2
Q2P, Q2AP TR1246 TRANSISTOR PNP TIP36E 2
Q3P TR1247 TRANSISTOR NPN TIP32E 1
Q4P TR1248 TRANSISTOR PNP TIP31E 1
REF. NO. PART NO. DESCRIPTION QTY
Miscellaneous
L1 SA0000042 AIR CORE INDUCTOR 1.8uH MI 1
LED1 LE1032 LED BICOLOR RED/GREEN 5mm. PI 1
SW1 SW1070 SWCH SLIDE SP3T RIGHT AN PI 1
24 SW1075 SWITCH ROCKER 2P2T 1
SNAP (230V ONLY)
TH1 TH1006 NTC THERMISTOR 10KΩ@25 P 1
TRIAC TY1001 MAC224-4 TRIAC 200V 25A 1
XFORMR MI1130 POWER TRANSFORMER (120V) 1
MI1176 POWER TRANSFORMER (230V) 1
Date Rev. No. Changes Made
3/21/96 1 Increment And Transistor Voltage To 140v
6/19/96 2
R11 changed from 27K to 51K
R12 changed from 51K to 24K
R9 changed from 20K to 200K
R10 changed from 33K to 200K
R29 changed from 11K to 33K
R51 changed from 160K to 470K
R39 changed from 47K to 10K
R54 changed from 47K to 10K
R22 changed from 15K to 4.7K
R34 changed from 15K to 4.7K
R20 changed from 220 to 160
R40 changed from 220 to 160
R33 changed from 4.3K to 4.7K
C5 changed from .1 µF to .033 µF
C7 changed from .1 µF to .033 µF
C11 changed from .1 µF to .022 µF
C15 changed from .047 µF to 3300 ρF
C21 changed from 100 ρF to 330 ρF
Fuse changed from 3A to 5A
C19 changed from 22 µF/16V to 22 µF/63V
C28 changed from 22 µF/16V to 22 µF/63V
R5P changed from 10 to 5.1
R6P changed from 10 to 5.1
C1 changed from 4700 µF/50V to 4700 µF/63V
C2 changed from 4700 µF/50V to 4700 µF/63V
Date Rev. No. Changed Made
6/19/96 3
R was added from 100 -Dwg Rev.03
C was added from 0.1 µF/100V -Dwg Rev.03
CX, CY added from 470 ρF - Dwg Rev.03
6/24/96 4
PC1132-1 was changed to PC1132-2
Q1AP was added
R1AP, R2AP were added from 0.1ohm
Q2AP was added
R2P was added from 100
C4P was added from 0.1 µF/100V
CX, CY were changed from 470 ρF to C2P, C3P
DIP, D2P were deleted
7/290/96 5
R20 changed from 220 to 160
R40 changed from 220 to 160
R5P changed from 10 to 5.1
R6P changed from 10 to 5.1
7/29/96 4
R29 was deleted from 33K
R9 was deleted from 200K
R51 was deleted from 470K
R10 was deleted from 200K
C7 was deleted from 0.033 µF 10%
R29 was added from 33.2K 1%
R9 was added from 200K 1%
R51 was added from 475K 1%
R10 was added from 200K 1%
C7 was added from 0.033 µF5%
REVISIONS

10
Powered Subwoofer BASS20
BASS20 PACKAGING VIEW (MUSIC20 & SCS120)

11
Powered Subwoofer BASS20
PRINTED CIRCUIT BOARDS (TOP VIEW)

12
Powered Subwoofer BASS20
PRINTED CIRCUIT BOARDS (BOTTOM VIEW)

13
Powered Subwoofer BASS20
INTEGRATED CIRCUIT DIAGRAM

14
Powered Subwoofer BASS20
120V SCHEMATIC DIAGRAM

14
Powered Subwoofer BASS20
120V SCHEMATIC DIAGRAM

15
Powered Subwoofer BASS20
230V SCHEMATIC DIAGRAM

15
Powered Subwoofer BASS20
230V SCHEMATIC DIAGRAM