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– 9 –

The idling adjustment should be executed on the L-CH and R-CH
of the POWER AMP board respectively.

Procedure:
1. Connect the digital voltmeter to TP1 and TP2 on the POWER

AMP board.

2. Turn fully the VR901 counterclockwise. (*1)
3. Turn on the power.
4. Turn the VR901 (*2) so that a reading on the digital voltmeter

is in a range of 1mV to 3mV in the center of 2mV. (*3)

5. In the same manner, adjust another POWER AMP board.

*1: This prevents over current from flowing. If over current flows, the

 protector works to disable the amplifier.

*2: The idling current increases when VR901 is turned clockwise, or

decreases by counterclockwise turn.

*3: The voltage will fluctuate sensitively, thus requiring careful

 adjustment.

Adjustment Location: See page 10 .

Digital voltmeter

TP1
TP2

POWER AMP board (L-CH or R-CH)

+
–

Check it without canceling the protector.

The protector check should be executed on the L-CH and R-CH
of the POWER AMP board respectively.

Procedure:
1. Turn on the power, and short the SPEAKER OUT terminal

(CN812 or CN813) and +12V terminal (CN814) on the
POWER AMP board.

2. The protector will work, then confirm that the OFFSET LED

(D851) color changes lighting green to flashing red and the
output is turned off.

3. Open the SPEAKER OUT terminal and +12V terminal.
4. Confirm that the protector is not reset.
5. Turn off the power once, and turn it on again, then confirm

that the protector does not work.

Checking Location: See page 10 .

Procedure:
1. Turn on the power, and short TP2 and TP3 on the POWER

AMP board.

2. The protector will work, then confirm that the OVER CUR-

RENT LED (D852) color changes lighting green to flashing
red and the output is turned off.

3. Open the TP2 and TP3.
4. Confirm that the protector is not reset.
5. Turn off the power once, and turn it on again, then confirm

that the protector does not work.

Checking Location: See page 10 .

Procedure:
1. Turn on the power, and short TP4 and TP5 on the POWER

AMP board.

2. The protector will work, then confirm that the THERMAL LED

(D855) color changes lighting green to flashing red, the fun
motor (M810 or M811) rotates, and the output is turned off.

3. Open the TP4 and TP5.
4. Confirm that the protector is reset.

Checking Location: See page 10 .

– 10 –

+

+

+

+

TP3

TP2

C919

TP1

C920

C917

C916

TP5

TP4

VR901  Idling Adjustment

D854

D853

D855

THERMAL

D851

OFFSET

D852

OVER CURRENT

CNB807

CN814 +12V (L/R) terminals

CN813

LEFT

SPEAKER OUT

terminals

CN812
RIGHT

– 11 –

POWER AMP board (L-ch)

PRE AMP board

LED board

POWER AMP board (R-ch)

PROTECT board

– 12 –

Note on Printed Wiring Board:
•

X

: parts extracted from the component side.

•

Y

: parts extracted from the conductor side.

•

b

: Pattern from the side which enables seeing.

(The other layers' patterns are not indicated.)

• All capacitors are in µF unless otherwise noted.  pF: µµF

50 WV or less are not indicated except for electrolytics
and tantalums.

• All resistors are in 

Ω

 and 

1

/

4

 

W or less unless otherwise

specified.

•

2

: nonflammable resistor.

•

C

: panel designation.

•

U

: B+ Line.

•

V

: B– Line.

•

H

: adjustment for repair.

• Power voltage is dc 14.4V and fed with regulated dc power

supply from +12V terminal (CN814) and REMOTE termi-
nal (CNJ803).

• Voltages and waveforms are dc with respect to ground

under no-signal conditions.

• Voltages are taken with a VOM (Input impedance 10 M

Ω

).

Voltage variations may be noted due to normal produc-
tion tolerances.

• Waveforms are taken with a oscilloscope.

Voltage variations may be noted due to normal produc-
tion tolerances.

• Circled numbers refer to waveforms.
• Signal path.

F

: AUDIO

Caution:
Pattern face side:

Parts on the pattern face side seen from

(Conductor Side)

the pattern face are indicated.

Parts face side:

Parts on the parts face side seen from

(Component Side) the parts face are indicated.