AVR 10 (serv.man5) - Harman Kardon Audio Technical Bulletin (repair manual)

harman/kardon Incorporated, 80 Crossways Park West, Woodbury, New York 11797 (516) 496 3400 

 
 

 
Service bulletin # 9601 - January 1996 

 

 

Warranty labor rate: MINOR repair  

 
To: All harman/kardon Service Centers 
 
Models: AVR10 / AVR-20 / AVR-20II Surround receivers 
 
Subject: Intermittent Mute in FM or No FM 
_____________________________________________________________________________________ 
 
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. 
 
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 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) 
 
3) Check and align the Center Tune Detect frequency as shown in the alignment instructions below. 
 
 
Alignment 
 

Equipment settings 

point 

Adjust for 

Center Tune 

Tune to a strong FM station around 
the center of the FM band (98.1MHz) 

DC mV 
meter across 
R809 

T803 

Less than 50 mV DC