Harman Kardon AVR 25 (serv.man4) Service Manual / Technical Bulletin ▷ View online
harman/kardon Incorporated, 80 Crossways Park West, Woodbury, New York 11797 (516) 496 3400
harman/kardon
Service Bulletin
Service bulletin # 9602 - January 1996
Warranty labor rate: MINOR repair
To: All harman/kardon Service Centers
Models: AVR25 / AVR 25 II Surround receivers
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 T903 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:
1) Locate on the tuner PCB coil T903 and R914
2) If the value of R914 is either 47 kOhm or 56 kOhm, solder a 56 kOhm resistor in parallel with R914.
(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
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
R914
meter across
R914
T903
Less than 50 mV DC
Display
