Test Setup And Procedure - JBL PowerBass PB12 Service Manual

PB12
PB12 TEST SETUP AND PROCEDURE
CD PLAYER
PRE AMP
AMPLIFIER
General Function
UUT = Unit Under Test
1. Connect one line level input cable (RCA) from signal generator to either Right or Left Level input on UUT. VOLUME
control should be full conterclockwise. Make sure the LFE/Normal switch is in the NORMAL position.
2. Turn on generator, adjust to 100mV, 50Hz.
3. Plug in UUT; Turn Main Power switch ON. LED's on the front panel may be either Red or Green. Turn VOLUME
control full clockwise. Low Pass control should be set fully clockwise (150Hz).
4. LED should turn Green; immediately bass response should be heard and felt from port tube opening.
5. Turn off generator, turn VOLUME control fully counterclockwise, disconnect RCA cables.
6. Connect one pair of speaker cables to either high level input terminal on UUT. Cables should be connected to an
integrated amplifier fed by the signal generator.
7. Turn on generator and adjust so that speaker level output is 1.0V, 50Hz. Turn VOLUME control full clockwise.
8. Green LED should light, immediate bass response should be heard and felt from the 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 unusual noises are heard, remove driver and test.
Driver Function
1. Remove driver from cabinet; detach + and – wire clips.
2. Check DC resistance of driver; it should be 4.8 ohms.
3. Connect a pair of speaker cables to driver terminals. Cables should be connected to an integrated amplifier fed by a
signal 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.
AC VOLT
METER (6V)
LINE LEVEL
PB12
UNDER TEST
SPEAKER
LEVEL
FROM
LINE-LEVEL
SOURCE
SPEAKER
OUTPUT
FROM
AMPLIFIER
12
LEVEL
Min Max
LFE NORMAL
PHASE 0 180
CROSSOVER
FREQUENCY
50 Hz 150 Hz
PowerBass PB12
L R
LI NE LEVEL I N
LFE
FOR USE L or R
L
HIGH
LIVEL
IN
R
L
HIGH
LIVEL
OUT
R