XM-754SX - Sony Car Audio Service Manual (repair manual). Page 8

8

+

_

Stabilized 

Power supply

Digital

Voltmeter

B+,REM terminals

set

GND terminal

test points

Note : The Bias adjustment should be performed only if any of

Q109 and Q110 for RV104, Q209 and Q210 for RV204,
Q309 and Q310 for RV304, and Q409 and Q410 for RV404
are replaced.

Procedure:
1. Rotate variable resistors RV104 (FRONT L-CH), RV204

(FRONT R-CH), RV304 (REAR L-CH) and RV404 (REAR
R-CH) full clockwise as seen from the pattern side to minimize
the bias current.

2. The input signal is with no signal.
3. Connect the stabilized power supply between B+ and REM

terminals and gradually increase the voltage to 14.4 V while
checking for any abnormal current.

4. Adjust RV104 (FRONT L-CH), RV204 (FRONT R-CH), RV304

(REAR L-CH) and RV404 (REAR R-CH) so that the digital
voltmeter connected between the respective test points reads
19.5±0.5 mV.

5. After this adjustment, verify that the current value of the

stabilized power supply is 5 A.
(With the set warmed, the current value is descreased to about
2.5 A. With the set being cooler, the more current flows. If the
current value is out of specification, wait until the set is cooler
before readjusting.)

RV Ref. No.

Test points

RV104

TP11 and TP12

RV204

TP21 and TP22

RV304

TP31 and TP32

RV404

TP41 and TP42

TP31

TP32

TP42

TP41

TP21

TP22

TP11

TP12

– MAIN BOARD (CONDUCTOR SIDE) –

RV104

BIAS ADJUSTMENT

(FRONT L-CH)

RV204

BIAS ADJUSTMENT

(FRONT R-CH)

RV304

BIAS ADJUSTMENT

(REAR L-CH)

RV404

BIAS ADJUSTMENT

(REAR R-CH)