JBL JSR 625 (serv.man3) Service Manual / Technical Bulletin ▷ View online
JBL Consumer Products, 80 Crossways Park West, Woodbury, New York 11797 (516) 496 3400
Service Bulletin
80 Crossways Park West
Woodbury, New York 11797
Service bulletin # 9607 - JULY 1996
Warranty labor rate: MINOR repair
To: All Service Centers
Model: JSR625
Subject: Intermittent Mute in FM or No FM
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In the subject models, the Audio signals from the MPX decoder are muted under two conditions:
1) When signal strength is low
2) When the voltage output from the Center Tune Detect (CTD) circuit is not zero. The CTD circuit
prevents the Tuner from stopping on the side bands of FM stations while in the SEEK mode.
Adjustable Coil T803 determines the CTD frequency.
1) When signal strength is low
2) When the voltage output from the Center Tune Detect (CTD) circuit is not zero. The CTD circuit
prevents the Tuner from stopping on the side bands of FM stations while in the SEEK mode.
Adjustable Coil T803 determines the CTD frequency.
In the event you receive a unit from a consumer with a complaint “FM cuts out intermittently”, perform
the following steps:
the following steps:
1) Locate on the tuner PCB coil T803 and R809.
2) If the value of R809 is either 47 kOhm or 56 kOhm, solder a 56 kOhm resistor in parallel with R809.
(By adding this resistor, the bandwidth of the CTD circuit is increased)
(By adding this resistor, the bandwidth of the CTD circuit is increased)
3) Check and align the Center Tune Detect frequency as shown in the alignment instructions below.
Alignment
Equipment settings
Connect
Adjustment
point
point
Adjust for
Center Tune
Tune to a strong FM station around
the center of the FM band (98.1MHz)
the center of the FM band (98.1MHz)
DC mV
meter across
R809
meter across
R809
T803
Less than 50 mV DC
Display
