harman/kardon
Service Bulletin
Service bulletin # 9502 - February 1995
Warranty labor rate: MAJOR repair
To: All harman/kardon Service Centers
Models:AVR-20/AVI-150 Surround receiver/amplifier
Subject: Low impedance protect circuit, intermittend shut down.
The power rating for the AVR-20 and AVI-150 is 60 Watts into 8 Ohms. The AVR-20 and AVI-150
protection circuits will not activate until the loudspeaker impedance drops below 4 Ohms. During
transients in certain CD program material, the instantaneous impedance of some loudspeakers with
impedance ratings of “8 Ohms” can drop well below 4 Ohms. As result, the low impedance protection
circuit will be activated.
In the event you receive from a consumer one of these products with the complaint “unit shuts down
intermittendly” change the components indicated in the table below. After the change, confirm the idling
current by measuring the voltage between the emitters of the output transistors. The test points are
TP1/TP2 and TP3/TP4. The voltage reading should stabilize at 26 mV after the unit has been switched on
for at least 15 minutes.
If needed, adjust idling current potentiometers VR251L/VR251R until you read 26 mV.
Change
From
To
Part #
Driver Transistor Q214L/214R
2SC2690(A)
2SC4883(A)
2028307101
Driver Transistor Q215L/Q215R 2SA1220(A)
2SA1859(A)
2028007101
Power Transistor Q216L/Q216R 2SC3181 (O)
2SC3182(O)
2028307101
Power Transistor Q217L/Q217R 2SA1264(O)
2SA1265(O)
2028007101
Resistor
R244L/244R
1.8kOhm
1.8kOhm 1/8 W
GD05182160
Resistor
R243L/R243R
2.2 kOhm
2.0 kOhm 1/8 W
1-118-202-25
Capacitor *
C223L/C223R
0.068mfd
10.0 mfd 16 V
E510601610
*Minus to emitter of Q218L / Q218R