Read JBL MUSIC 2 SUB (serv.man2) Service Manual online
4
Powered Subwoofer
BASS2/BASSWAVE
TEST PROCEDURES
Equipment needed:
n
Functional/signal generator
n
True RMS Multimeter
n
Integrated amplifier
n
Cables - line level (RCA) and speaker cables
n
RCA Y-cable
General Function
UUT = Unit Under Test
1.
Connect both right and left line level inputs (RCA)
to signal generator and UUT. Assure input
button is in depressed position. Use Y-cable if
necessary from mono source.
to signal generator and UUT. Assure input
button is in depressed position. Use Y-cable if
necessary from mono source.
2.
Turn on generator, adjust to 50 mV, 50 Hz. Plug
in UUT, turn level control full clockwise.
in UUT, turn level control full clockwise.
3.
Green LED should light, immediate bass response
should be heard and felt from port tube openings.
should be heard and felt from port tube openings.
4.
Turn off generator, unplug unit, disconnect RCA
cables.
cables.
5.
Connect two pair of speaker cables to high level
input terminal on UUT. Assure input button is in
extended (out) position. Cables should be
connected to an integrated amplifier fed by the signal
generator. Observe polarity of speaker cables.
input terminal on UUT. Assure input button is in
extended (out) position. Cables should be
connected to an integrated amplifier fed by the signal
generator. Observe polarity of speaker cables.
6.
Turn on generator and adjust so that speaker level
output is 2.0V, 50 Hz. Plug in UUT, turn level
control full clockwise.
output is 2.0V, 50 Hz. Plug in UUT, turn level
control full clockwise.
7.
Green LED should light, immediate bass response
should be heard and felt from port tube openings.
should be heard and felt from port tube openings.
Sweep Function
1.
Connect both right and left line level inputs (RCA) to
signal generator and UUT. Assure input button is
in depressed position. Use Y-cable if necessary
from mono source.
signal generator and UUT. Assure input button is
in depressed position. Use Y-cable if necessary
from mono source.
2.
Turn on generator, adjust to 50 mV. Plug in UUT,
turn level control full clockwise.
turn level control full clockwise.
3.
Green LED should light, immediate bass response
should be heard and felt from port tube openings.
should be heard and felt from port tube openings.
4.
Sweep generator from 20 Hz to 300 Hz. Listen to
the cabinet and drivers for any rattles, clicks,
the cabinet and drivers for any rattles, clicks,
buzzes or any other noises. If any unusual noises
are heard, remove driver and test.
are heard, remove driver and test.
Driver Function
1.
Follow instructions on page 2 (“To Access Lower
Woofer”).
Woofer”).
2.
Check DC resistance of driver; it should be
approximately 5.2 ohms. Upper (non-removable)
driver can be checked by disconnecting both the
wires to the amplifier and the lower driver, then
connecting the test meter to the wires.
approximately 5.2 ohms. Upper (non-removable)
driver can be checked by disconnecting both the
wires to the amplifier and the lower driver, then
connecting the test meter to the wires.
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 4.0V.
Cables should be connected to an integrated
amplifier fed by a signal generator. Turn on
generator and adjust so that speaker level output
is 4.0V.
4.
Sweep generator from 20 Hz to 1KHz. Listen to
driver for any rubbing, buzzing, or other unusual
noises.
driver for any rubbing, buzzing, or other unusual
noises.
* The upper woofer in non-serviceable. Order
replacement cabinet/upper driver assy.
(Part#BASSWAVEENCLKIT). Also cone/diaphram
kits not available, defective drivers should be
replaced.
replacement cabinet/upper driver assy.
(Part#BASSWAVEENCLKIT). Also cone/diaphram
kits not available, defective drivers should be
replaced.
Service Notes/Revisions
In the event you receive a unit with the complaint that
the unit “shuts down after it is on for a while", usually
about 10-15 minutes. (Verify the R46 has not been
changed with a jumper already; then proceed with
modification of the amplifier unit).
the unit “shuts down after it is on for a while", usually
about 10-15 minutes. (Verify the R46 has not been
changed with a jumper already; then proceed with
modification of the amplifier unit).
This should be performed on units with circuit board
marked Rev. 001 to Rev. 003.
marked Rev. 001 to Rev. 003.
If you have found output devices Q4 or Q5 shorted,
replace with matched pairs only. This is critical for
proper amplifier operation.
replace with matched pairs only. This is critical for
proper amplifier operation.
Procedure: Locate R46 (33 ohm) and replace it with a
22 gauge jumper wire. After verifying normal turn-on,
load the amp with a 4 ohm watt resistor and apply a
70 Hz, 200 mV signal to one RCA input jack. Let the
amp run for about 20 minutes to confirm the amp no
longer shuts down.
22 gauge jumper wire. After verifying normal turn-on,
load the amp with a 4 ohm watt resistor and apply a
70 Hz, 200 mV signal to one RCA input jack. Let the
amp run for about 20 minutes to confirm the amp no
longer shuts down.
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