JBL TLX PS12 Service Manual / Technical Bulletin ▷ View online
JBL Incorporated 250 Crossways Park Dr. Woodbury, New York 11797 (516) 496-3400
Service Bulletin
Service Bulletin JBL9907 - August 1999
Warranty labor rate: MINOR repair
To:
All JBL Service Centers
Model: TLX PS10, TLX PS12
Subject: Premature muting
Some customers may experience a tendency for the TLX PS10 or TLX PS-12 Subwoofers to “mute” or shut
down when played at a low level and when negligible bass information is present. Actually, this is normal
behavior for the subwoofer. If the unit was designed to be extremely sensitive, the bass amplifier could sense
small amounts of 60 Hz hum or noise picked up by the customer's input cables, random RF noise, etc. and the unit
would never turn off.
down when played at a low level and when negligible bass information is present. Actually, this is normal
behavior for the subwoofer. If the unit was designed to be extremely sensitive, the bass amplifier could sense
small amounts of 60 Hz hum or noise picked up by the customer's input cables, random RF noise, etc. and the unit
would never turn off.
In the event that you receive a TLX PS10 or TLX PS-12 Subwoofer with the complaint “the subwoofer is
shutting off with low levels of music, or during long quiet pauses during movie viewing”, perform the
following modification to increase the sensitivity of the unit from 7.0 mV to 0.5 mV:
shutting off with low levels of music, or during long quiet pauses during movie viewing”, perform the
following modification to increase the sensitivity of the unit from 7.0 mV to 0.5 mV:
1) Remove (10) Philips screws around the outside of the amplifier faceplate; remove amplifier assembly from
cabinet.
2) Remove both control knobs, nuts, and all Philips screws shown in Figure 1.
3) Detach amp assembly and heatsink from rear of amplifier faceplate.
4) Change R33 from 220K
3) Detach amp assembly and heatsink from rear of amplifier faceplate.
4) Change R33 from 220K
Ω
to 1Meg
Ω
(JBL part# 108550)
5) Change C21 from 470pf to 100pf (JBL part# 3579101130)
6) Replace amplifier assembly in reverse order and test unit.
6) Replace amplifier assembly in reverse order and test unit.
Model
Serial number 120V
Status
Action
TLX PS10
All serial
numbers affected
May need modification
Change R33 to 1Meg
Ω
Change C21 to 100pf
TLX PS12
All serial
numbers affected
May need modification
Change R33 to 1Meg
Ω
Change C21 to 100pf
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