JBL powered Sub-woofer S120PII - Schematic - Exploded view - Test procedure and specs; 400Watts RMS output - Studio Series
The
S120PII is equipped with both a master power switch and an auto turn-off
switch. In order to function, the sub
woofer must be plugged into an active electrical outlet [but not an accessories
outlet on another component of your audio system, such as a receiver], and the
master power switch must be turned ON.
Distortion When Coming Out Of Standby
In the event you receive an S120PII sub-woofer with the complaint “There is a brief chirping sound or short oscillation that occurs when the unit is in the AUTO mode, in Standby, when it’s triggered ON with a music signal”, follow the procedure below to correct this condition:
Synopsis: Replace D60 (RLS4148 diode) with a 3.6V Zener Diode; add new Resistor.
1) Remove the amplifier assembly from the sub-woofer cabinet (12 Phillips screws).
2) Remove the Plastic Amp Cover from the face-plate (4 Phillips screws).
3) The area of concern is on the Class D Driver PCB (Small Upright PCB on the MAIN AMP PCB). A long, thin, soldering iron tip is recommended. Care must be taken not to damage surrounding components, like large inductor pair L8.
4) Locate, remove D60 (RLS4148 diode); replace with a 3.6V zener diode, JBL Part# ZMM5227BCT-ND. When replacing D60 the polarity of the new (zener) diode should be reversed.
5) Add new 27KΩ resistor, JBL Part# 299-27K, to the indicated connections. (This component, electrically, will be in parallel with R37, reducing its value to <22KΩ). Assure the leads do not come into contact with any other connections; insulate the leads if necessary.
6) Replace amp cover and return amplifier assembly to cabinet.
7) Test the sub-woofer to assure the distortion is no longer present.
Circuit diagram [Click on the pictures to magnify]
Exploded view
JBL S120PII SPECIFICATIONS
Amplifier Power (RMS): 400 Watts
Driver: 12" PolyPlas™ (polymer-coated cellulose fiber) (4.4 ohms DCR)
Inputs: Line Level (switchable to LFE), BassQ™ and Speaker Level
Outputs: BassQ and Speaker Level (High-Pass)
Low-Pass Frequency: Continuously variable from 50Hz – 150Hz
High-Pass Frequency: 150Hz when using speaker-level outputs
Frequency Response: 22Hz – Low-pass crossover setting
Dimensions (H x W x D): 17-3/16" x 16-3/16" x 18" (19" with grille) (with feet, without spikes) 437 x 411 x 457mm (483mm with grille)
Weight: 56 lb/25.5kg
Driver: 12" PolyPlas™ (polymer-coated cellulose fiber) (4.4 ohms DCR)
Inputs: Line Level (switchable to LFE), BassQ™ and Speaker Level
Outputs: BassQ and Speaker Level (High-Pass)
Low-Pass Frequency: Continuously variable from 50Hz – 150Hz
High-Pass Frequency: 150Hz when using speaker-level outputs
Frequency Response: 22Hz – Low-pass crossover setting
Dimensions (H x W x D): 17-3/16" x 16-3/16" x 18" (19" with grille) (with feet, without spikes) 437 x 411 x 457mm (483mm with grille)
Weight: 56 lb/25.5kg
SYSTEM AURAL SWEEP TEST
Equipment needed:
* Function/signal generator/sweep generator
* Integrated Amplifier
* Multimeter
* Speaker cables
* RCA phono cables (pair)
General Unit Function (UUT = Unit Under Test)
Switches/knobs on the amplifier faceplate:
Crossover Frequency Adjust full CW (150Hz)
Phase switch – either position
Normal/LFE switch – Normal
Auto On/Off - either position
1. From the signal generator, Connect both right and left line level inputs (RCA jacks) – to signal generator and UUT. Use Y-cable if necessary from mono source.
2. On the amplifier, turn the LEVEL control full Counterclockwise (Min).
3. Turn on generator, adjust to 100mV, 50 Hz.
4. Plug in UUT; turn the power switch ON. Turn LEVEL control full Clockwise (Max).
5. LED’s (top of UUT) should now be Green; immediate bass response should be heard and felt from port tube opening.
6. Turn LEVEL control full Counterclockwise (Min). Turn power switch OFF.
7. Connect one pair of speaker cables to one set (either R or L) of the Speaker Input terminals on UUT. Cables should be connected to an integrated amplifier fed by the signal generator.
8. Turn on signal generator and adjust so that speaker level output at the amplifier is 2.5V, 50 Hz.
9. Turn power switch ON; turn LEVEL control full Clockwise (Max).
10. Bass response should be heard and felt from port tube opening.
Sweep Function
1. Follow steps 1-5 above, using a sweep generator as a signal source.
2. Sweep generator from 20Hz to 1kHz. Listen to the cabinet and drivers for any rattles, clicks, buzzes or any other noises. If any unusual noises are heard, remove woofer and test.
Driver Function (Woofer)
1. Remove woofer from cabinet; detach + and - wire clips.
2. Check DC resistance of woofer; it should be 4.4 ohms±10%.
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.
Equipment needed:
* Function/signal generator/sweep generator
* Integrated Amplifier
* Multimeter
* Speaker cables
* RCA phono cables (pair)
General Unit Function (UUT = Unit Under Test)
Switches/knobs on the amplifier faceplate:
Crossover Frequency Adjust full CW (150Hz)
Phase switch – either position
Normal/LFE switch – Normal
Auto On/Off - either position
1. From the signal generator, Connect both right and left line level inputs (RCA jacks) – to signal generator and UUT. Use Y-cable if necessary from mono source.
2. On the amplifier, turn the LEVEL control full Counterclockwise (Min).
3. Turn on generator, adjust to 100mV, 50 Hz.
4. Plug in UUT; turn the power switch ON. Turn LEVEL control full Clockwise (Max).
5. LED’s (top of UUT) should now be Green; immediate bass response should be heard and felt from port tube opening.
6. Turn LEVEL control full Counterclockwise (Min). Turn power switch OFF.
7. Connect one pair of speaker cables to one set (either R or L) of the Speaker Input terminals on UUT. Cables should be connected to an integrated amplifier fed by the signal generator.
8. Turn on signal generator and adjust so that speaker level output at the amplifier is 2.5V, 50 Hz.
9. Turn power switch ON; turn LEVEL control full Clockwise (Max).
10. Bass response should be heard and felt from port tube opening.
Sweep Function
1. Follow steps 1-5 above, using a sweep generator as a signal source.
2. Sweep generator from 20Hz to 1kHz. Listen to the cabinet and drivers for any rattles, clicks, buzzes or any other noises. If any unusual noises are heard, remove woofer and test.
Driver Function (Woofer)
1. Remove woofer from cabinet; detach + and - wire clips.
2. Check DC resistance of woofer; it should be 4.4 ohms±10%.
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.
