Service Bulletin Jbl2001-02 - February 2001 - JBL PSW-D112 Service Manual

Service Bulletin JBL2001-02 - February 2001

To: All JBL Service Centers
Models: PSW-D112 rev0*, DPS-12, PSW-D115
Subject: Check Ribbon Cable Connection In Event Of Failure
Some performance related complaints in the PSW-D or DPS Series powered Subwoofers may be caused by
broken or cold solder connections in the ribbon cable connector between the premamp and main PCB.
When this condition occurs, it may also damage the Input Op-Amps U1/U2.
When troubleshooting, failure to check this connector and Input Op-Amps U1/U2 can result in erroneous
conclusions or wasted time.
In the event you receive a PSW-D112*, DPS-12, or PSW-D115 Subwoofer with any of the complaints
"Dead, or No Output, or Motorboating (Oscillation)", perform the steps listed below before any further
troubleshooting takes place:
1) Unplug all cables, lay the subwoofer on a padded surface.
2) Remove all Philips screws around the outer perimeter of the amplifier faceplate.
3) Remove amplifier assembly; you should be able to remove the amplifier far enough out of the cabinet to service it
without removing other connecting wires.
4) Locate the ribbon cable connector between the premamp PCB and the main PCB. See illustration.
5) Desolder the connection on that cable where the cable attaches to the premamp PCB; to access, you may have to
carefully remove or scrape adhesive from this area.
6) Cut approximately ½" of ribbon from the cable end, then strip enough of the insulator on each of the six conductors
to allow re-connection. Take care not to damage the wire. Solder the cable end back onto the premamp PCB.
7) Test the unit by applying a signal from a music source, adjust the volume to a moderate level and confirm the
original problem has been corrected.
8) If not, troubleshoot Op-Amps U1 and U2 by standard methods; replace if defective:
Make sure plus/minus voltages are present on pins 4 and 11.
Make sure DC voltages are not present at output pins 1,7,8,14. (See schematic)
Apply a signal and confirm there is an output on pins 1,7,8,14. (See schematic)
9) Replace the amplifier assembly back into the cabinet; replace the screws.
* Rev 0 of the PSW-D112 subwoofer is easily identified by the presence of Center channel Input and Output connectors
JBL Incorporated
IMPORTANT SERVICE NOTES: When testing the
PSW-D or DPS Series amplifier, a load must
always be connected to the output terminals,
whether the woofer, or a 4 to 8 ohm resistive load.
All AC powered test instruments (meters,
oscilloscopes, etc.) must have a floating ground,
i.e. be connected to an isolation transformer.
250 Crossways Park Dr.
Service Bulletin
This is considered a Minor repair
Woodbury, New York 11797 (516) 496-3400
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