DOWNLOAD Harman Kardon AVR 5550 (serv.man14) Service Manual ↓ Size: 1.21 MB | Pages: 4 in PDF or view online for FREE

The Technical Team 

Harman Consumer Group International     2 route de Tours     72500 Château du Loir     FRANCE  

pin 32.FAN1-OUT for 
the Heat detection 
 

pin 33.FAN2-OUT for 
the Level detection 

AVR4550/5550 Quick Description on: 

FANS CONTROL 

 
 
The Fans depend of the heat and of the audio level on AVR4550 and AVR5550. 
IC12 (DSP board)  activate fans with a feedback of measures (the Level detection and the 
Heat detection). 
 

Location: 

- 

It takes the measure on N806 on MAIN board. The level measure goes to IC12 pin 
34.FANCONT on DSP board. 
Voltage: 

- 

The control of fans starts from > 2V4 pin 1 of N400 (DSP board), then it stops when the 
voltage is < 2V4 

 
 

Location: 

- 

It takes the measure from POSISTOR IN P071 and from POSISTOR IN P052. The Heat 
measure goes to IC12 pin 30.FAN1-IN and IC12 pin 31.FAN2-IN on DSP board. 
Voltage: 

- 

Start from > 1.80V pin 15 (4-CH THERMAL IN)  of P811 (MAIN board) and stops from 
<1.04V 

- 

Start from > 1.80V pin 14 (3-CH THERMAL IN)  of P811 (MAIN board) and stops from 
<1.04V 

 
Control : 

- 

In both case (Heat detection active or Level detection active) Fan 1 and Fan 2 start always 
at the same time due to the CNT B’D with 2 diodes (see 

 

 
- 

Pin 12 of P811 (FRONT FAN OUT) is for the Heat detection (pin 32.FAN1-OUT of IC12). 
Fans are activated when pin 32 is active at 3V 

- 

Pin 13 of P811 (REAR FAN OUT) is for the Level detection (pin 33.FAN2-OUT of IC12). 
Fans are activated when pin 33 is active at 3V 

 
- 

On MAIN board Q601 turns on fan 1 or front fan and Q602 turns on fan 2 or rear fan. 

CNT B’D 

OUT LEVEL DET from 

MAIN b'd N400 P811 pin19

OUT LEVEL DET to DSP board N400 pin 1

HEAT DETECTION from 

3CH AMP board P307

HEAT DETECTION to DSP 

board N400 pin 14-15

HEAT DETECTION to MAIN board N808