JBL SUB125 TROUBLE SHOOTING AND CIRCUIT DIAGRAM
General Function
UUT = Unit Under Test
1. Connect both right and left line level inputs (RCA) to signal generator and UUT. Use Y-cable if necessary from mono source. VOLUME control should be full counterclockwise.
2. Turn on generator, adjust to 200mV, 50 Hz.
3. Plug in UUT; red LED should be ON. Turn VOLUME control full clockwise.
4. LED should turn Green; immediate 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 both high level input terminals 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 3.0V, 50 Hz. 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 3.3 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.
UUT = Unit Under Test
1. Connect both right and left line level inputs (RCA) to signal generator and UUT. Use Y-cable if necessary from mono source. VOLUME control should be full counterclockwise.
2. Turn on generator, adjust to 200mV, 50 Hz.
3. Plug in UUT; red LED should be ON. Turn VOLUME control full clockwise.
4. LED should turn Green; immediate 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 both high level input terminals 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 3.0V, 50 Hz. 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 3.3 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.
SIMPLE TROUBLESHOOTING
If there is no sound from any of the speakers,
check the following:
# Receiver/amplifier is on and a source is playing.
# Powered subwoofer is plugged in and is either in the “On” or “Auto” position.
# Check all wires and connections between receiver/ amplifier and speakers. Make sure all wires are connected. Make sure none of the speaker wires are frayed, cut or punctured.
# Review proper operation of your receiver/amplifier. If there is no sound coming from one speaker, check the following:
# Check the “Balance” control on your receiver/amplifier.
# Receiver/amplifier is on and a source is playing.
# Powered subwoofer is plugged in and is either in the “On” or “Auto” position.
# Check all wires and connections between receiver/ amplifier and speakers. Make sure all wires are connected. Make sure none of the speaker wires are frayed, cut or punctured.
# Review proper operation of your receiver/amplifier. If there is no sound coming from one speaker, check the following:
# Check the “Balance” control on your receiver/amplifier.
If the system plays at low volumes but shuts off
as volume is increased, check the following:
# Check all wires and con-nections between receiver/ amplifier and speakers. Make sure all wires are connected. Make sure none of the speaker wires are frayed, cut or punctured.
# If more than one pair of main speakers is being used, check the minimum impedance requirements of your receiver/amplifier.
# Check all wires and con-nections between receiver/ amplifier and speakers. Make sure all wires are connected. Make sure none of the speaker wires are frayed, cut or punctured.
# If more than one pair of main speakers is being used, check the minimum impedance requirements of your receiver/amplifier.
If there is low bass output, check the following:
# Make sure the connections to the left and right “Speaker Inputs” have the correct polarity (+ and –).
# Powered subwoofer is plugged in and is either in the “On” or “Auto” position.
# Make sure the connections to the left and right “Speaker Inputs” have the correct polarity (+ and –).
# Powered subwoofer is plugged in and is either in the “On” or “Auto” position.
If there is no sound from the surround speakers,
check the following:
# Check all wires and connections between receiver/ amplifier and speakers. Make sure all wires are connected. Make sure none of the speaker wires are frayed, cut or punctured.
# Review proper operation of your receiver/amplifier and its surround sound features.
# Receiver mode must be in Dolby Pro logic, Dolby Digital, or any other mode that creates a surround-sound effect. Even under normal operation, when viewing movies and television, surround sound is not present at all times at a high volume - only when the program has chosen to send information there.
# Check all wires and connections between receiver/ amplifier and speakers. Make sure all wires are connected. Make sure none of the speaker wires are frayed, cut or punctured.
# Review proper operation of your receiver/amplifier and its surround sound features.
# Receiver mode must be in Dolby Pro logic, Dolby Digital, or any other mode that creates a surround-sound effect. Even under normal operation, when viewing movies and television, surround sound is not present at all times at a high volume - only when the program has chosen to send information there.
Amplifier plate overheating; Blown fuses
In the event you receive a Sub125 (SCS125
Powered Subwoofer) with the complaint “amplifier plate is getting too hot”, or
“the unit is blowing fuses”, perform the necessary steps listed below to change
the bias current of the amplifier. This procedure should be performed on all
Sub125 amplifiers being serviced for any reason:
1. Set the subwoofer cabinet on a padded surface with amplifier facing upwards.
2. Remove the (14) Philips screws holding the amplifier and inner plastic cover to the cabinet. Four of these 14 screws are in each corner, slightly larger and just inside the smaller corner screws.
3. Remove amplifier assembly carefully . Do not pull the amplifier out of the cabinet too much; it can disconnect the speaker wires. (The amp assembly can be laid on one corner of the cabinet for the remainder of the procedure without disconnecting the speaker wires).
4. Carefully pry plastic cover off amplifier assembly. If you are too aggressive Molex connector P104 may be damaged; speaker wire inside the cover has little extra length. Lift the left side of the cover first to avoid disconnecting the cable at P104; this connector is located on the right side of the plate inside the cover.
5. Once the cover is pulled back, locate VR101. See Figure .
1. Set the subwoofer cabinet on a padded surface with amplifier facing upwards.
2. Remove the (14) Philips screws holding the amplifier and inner plastic cover to the cabinet. Four of these 14 screws are in each corner, slightly larger and just inside the smaller corner screws.
3. Remove amplifier assembly carefully . Do not pull the amplifier out of the cabinet too much; it can disconnect the speaker wires. (The amp assembly can be laid on one corner of the cabinet for the remainder of the procedure without disconnecting the speaker wires).
4. Carefully pry plastic cover off amplifier assembly. If you are too aggressive Molex connector P104 may be damaged; speaker wire inside the cover has little extra length. Lift the left side of the cover first to avoid disconnecting the cable at P104; this connector is located on the right side of the plate inside the cover.
5. Once the cover is pulled back, locate VR101. See Figure .
6. Using a thin Phillips screwdriver 5 or more inches long, set trim pot VR101 to Full CCW position (Minimum level). Be gentle to avoid damage to the part.
7. If necessary, replace blown line fuse with h/k part# FS1067, (2A Slo-Blo 5 x 20mm GMC type).
8. Replace the amplifier in the cabinet; replace all (14) screws to secure the amplifier plate and plastic cover.*
9. Functional Test - Set the LEVEL control to minimum (Full CCW). Connect an AC Wattmeter to the AC input line and turn the unit ON; maximum AC measured power should not be more than 12.5 watts.
10. Connect music signal from a CD source and increase volume to a medium level to verify sound from the subwoofer. Do not increase volume to a point where the unit is driven into clipping. No evidence of distortion and/or rattle inside the box should occur.
11. Conduct warm-up for 10 minutes; turn LEVEL control Full CCW or remove signal. Input power as measured by AC Power meter should not exceed 13 watts. If value exceeds this, re-check pot. VR101 position if necessary.
12. Add an adhesive label (dot) to the amplifier plate with the letter “a” written on it; if the customer’s outer carton is available, add an “a” with a marker to the “SCS125” printing on the carton in all places where it appears.
CIRCUIT DIAGRAM
CLICK ON THE IMAGE TO ZOOM IN
