JBL MEDIA SYSTEM 2000 (serv.man8) Service Manual / Technical Bulletin ▷ View online
JBL Incorporated 250 Crossways Park Dr. Woodbury, New York 11797 (516) 496-3400
Service Bulletin
Service Bulletin JBL9802 - May 1998
Warranty labor rate: MAJOR repair
To:
All JBL Service Centers
Model: Media Sub2000 Powered Subwoofer
Subject: False Triggering
In the event you receive a Media Sub2000 with the complaint: “the subwoofer never shuts off”, or “the
unit cycles on & off by itself with no input signal”, perform the following modification to raise the input
threshold of the subwoofer amplifier:
unit cycles on & off by itself with no input signal”, perform the following modification to raise the input
threshold of the subwoofer amplifier:
Procedure:
1) Turn the unit upside-down and remove the (8) mounting screws on the bottom plate. This includes the (2)
deeply recessed screws near the center of the plate. Then remove the (2) smaller screws holding the
black input plate to the end of the cabinet.
black input plate to the end of the cabinet.
2) Pull the plate and amplifier up and out the cabinet.
3) Unplug all (3) molex connectors, and remove the (2) small screws holding the input plate onto the
3) Unplug all (3) molex connectors, and remove the (2) small screws holding the input plate onto the
amplifier PCB; remove the input plate.
4) To gain access to the components, remove the (2) remaining small screws holding the PCB to the bottom
plate and detach it from the plate.
5) Locate C351 - 100pf SMD cap. Replace with 470 pf part, (JBL part #CP1885). See drawing.
6) Locate R348 - 330K
6) Locate R348 - 330K
Ω
SMD resistor. Replace with 100k
Ω
part, (JBL part #RS2043).
7) Locate Diode D351. Solder a 10K
Ω
resistor (JBL part #RS2042) in parallel with the diode.
8) Reassemble and replace the amplifier assembly into the cabinet in the reverse order , making sure all
connectors and screws are replaced.* When re-attaching the input plate make sure both ground
terminals are attached to the screw.
terminals are attached to the screw.
9) Test unit and assure that the subwoofer stays in the standby mode with no input signal, and comes out of
protection with a 50 Hz, 50 mV input signal.
* When replacing the final two screws in the
center of the bottom plate, because of the
design you cannot drop the screws into each
cavity and expect the screws to align with the
holes.
With a Philips screwdriver well fitted to the
screw head, you may either use a magnetized
screwdriver and lower the tip (with screw)
carefully down into the cavity to align; OR
turn the subwoofer right-side up and insert the
tip with screw up into the cavity.
center of the bottom plate, because of the
design you cannot drop the screws into each
cavity and expect the screws to align with the
holes.
With a Philips screwdriver well fitted to the
screw head, you may either use a magnetized
screwdriver and lower the tip (with screw)
carefully down into the cavity to align; OR
turn the subwoofer right-side up and insert the
tip with screw up into the cavity.
Model
Serial number
120V
Serial number
230V
Status
Action
Media
Sub2000
AC0029-10001
to
AC0029-11300
False Triggering
Change value of C351 and R348; add 10K
Ω
resistor in parallel with D351
Media
Sub2000
AC0029-11301
and above
AC0030-01001
and above
Factory
Modification
NONE REQUIRED
Display