background image

3

Powered Subwoofer

BASS20

TEST PROCEDURE

Equipment Needed:

n

Function generator/signal generator/sweep generator

n

Integrated Amplifier

n

Multimeter

n

Cables - 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 LEDshould be ON. Turn power switch to the ON or AUTO position and turn LEVEL control

full clockwise.

4. Green LEDshould 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 LEDshould 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;  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.

Summary of Contents for JBL BASS20

Page 1: ...ERVICE MANUAL SERVICE 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 BASS2...

Page 2: ...nputs 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...

Page 3: ...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...

Page 4: ...TO 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...

Page 5: ...blies 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...

Page 6: ...5 Powered Subwoofer BASS20 BASS 20 120v US 230v European Versions BLOCK DIAGRAM...

Page 7: ...6 Powered Subwoofer BASS20 BASS20 120V 230V versions AMPLIFIER EXPLODED VIEW...

Page 8: ...7 Powered Subwoofer BASS20 BASS20 CABINET ASSEMBLY EXPLODED VIEW...

Page 9: ...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...

Page 10: ...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 R5...

Page 11: ...1 0 Powered Subwoofer BASS20 BASS20 PACKAGING VIEW MUSIC20 SCS120...

Page 12: ...1 1 Powered Subwoofer BASS20 PRINTED CIRCUIT BOARDS TOP VIEW...

Page 13: ...1 2 Powered Subwoofer BASS20 PRINTED CIRCUIT BOARDS BOTTOM VIEW...

Page 14: ...1 3 Powered Subwoofer BASS20 INTEGRATED CIRCUIT DIAGRAM...

Page 15: ...1 4 Powered Subwoofer BASS20 120V SCHEMATIC DIAGRAM...

Page 16: ...1 5 Powered Subwoofer BASS20 230V SCHEMATIC DIAGRAM...

Reviews: