Onkyo A 8051 Service Manual

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Ref. No. 3463

ONIrgro® SERVICE MANUAL

Integrated Stereo Amplifier

MODEL A-8051

[ UPV 230V7AC, iOHz 7

/ v

SAFETY-RELATED COMPONENT WARNING"

COMPONENTS IDENTIFIED BY MARK A ON
THE SCHEMATIC DIAGRAM AND IN THE
PARTS LIST ARE CRITICAL FOR RISK OF
PARTS.

WHOSE PARTS NUMBERS APPEAR AS SHOWN
IN THIS MANUAL. '

MAKE LEAKAGE-CURRENT OR RESISTANCE
MEASUREMENTS TO DETERMINE THAT EXP~
OSED PARTS ARE ACCEPTABLY INSULATED
FROM THE SUPPLY CIRCUIT BEFORE RET-
URNING THE APPLIANCE TO THE CUS-
TOMER.

\

TABLE OF CONTENTS

Specifications ...........................................
Adjustment procedures-- "
IC block dia ram ~~~~~~~
Front panel acilities ' , ~

Chassis exploded view ---------

Printed circuit board parts I' t -' .4 11
Parts list of packing ---------- ~ 14
Printed circuit board View '- ~ 15
Block diagram .............. . 19
Schematic diagram" ' 21

Precautions . .1 ......................................... 23

ONKYO

Alllllll IIIIMPIININIS

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SPECIFICATIONS

Power Output :

Total Harmonic Distortion :
Intermodulation Distortion :
Damping Factor :

Input Sensitivity [Impedancez

Output Sensitivity / Impedance :
Phono Overload :

Tone Control :

Frequency Response :
Signal to Noise Ratio (IHF-A) :

Power Supply :
Dimensions (W X H X D) :

Weight :

60 watts per channel, min. RMS,at 8 ohms,
both channels driven from 20 Hz to 20 kHz.
with no more than 0.06% THD.

2 X100 watt an 40hm. I kHz (DIN)

2 X 70 watt an 80hm, lkHz (DIN)
0.06% at rated power

0.06% at rated power

150 at 8 ohms (1 kHz)

Phono (MM): 2.5 mV / 50 kohms
Phono (MC): 350). V / 220 ohms
CD/Tuner/Line: 150 mV / 25 kohms

Tape Play: 150 mV / 25 kohms
Tape Rec: 150 mV / 3 kohms (Phono)
Phono (MM) : 135 mV RMS. at 1 kHz;
0.1% THD.
BASS: :l:8 dB at 100 Hz
TREBLE: i8 (18 at 10 kHz
Loudness Control: 5+ 8 dB at 100 Hz
+ 8 dB at 10 kHz
CD,Tuner: ISHZNSOKHZildB

Phono (MM): 84 dB (5.0 mV input)
Phono (MC): 74 dB (05 mV input)
CD (DIRECT): 104 dB (0.5V input)
AC 230V, 50 Hz

455 x150><348 mm

17-15/16" XS-7/8" X 13-11/16"

8.3 kg, (18.3 lbs.)

Specifications and features are subject to change without notice

ADJUSTMENT PROCEDURES \
Adlustments and Checking the Protection Circuitry

l. Preparations

1) Place the unit on the workbench. (There should be about 15 mm of space between the base plate of the unit and
the work surface.)

2) Set up the unit as follows.

L (1")Nouload ' '
(2) No signal
(3) Volume turned all the way down
(4) Speaker switch OFF
(5) Power iswitch OFF

Note) Check the following points before making adjustments
(1) The power switch should be OFF.
(2) The interior of the unit should not be warm.

2. Idling current adjustment
1) Turn the power switch 0N and allow the unit to warm up for about 10 minutes.

(1) Ajust R531 (R532) so that the voltage at test point VCT-ID on the NAAF-4838 circuit board is 9.5mVi3.5mV

NOTE) Senitixed resistors enclosed in parentheses ( ) are for the rixht channel.

3. Check of operation of protection circuitry
1) Check of operation of protection relay.
(1) Confirm that the relay turns ON appyoximately 5 seconds after the power switch is turned ON.
(2) The relay should turn OFF approximately 0.5 seconds after the power switch is turned OFF.
2) Check of DC detection ~

(1) Turn the power on with no load.
(2) After the speaker relay turns ON, apply DC +1 ~I.5V to the CD input terminals. Confirm that the relay turns OFF.

(3) Confirm that operation is the same as (2) above when an input of DC-l ~ -1.5V is applied.
Note) Under no circumstances connect 51656 oration the speaker terminals when performing the above test.
3) Confirmation of current detection operation
(1) Signal input from the circuit illustrated below with no load.
(2) Confirm that the speaker relay does not turn OFF even when a 2 ohm load is connected when a peak value of 35Vp
is output.
(3) Next, confirm that when a 1 ohm load is connected the speaker relay switches OFF and ON a couple of times
and then stays OFF.
Note) The period before that relay stays OFF should not last for more than [0 second.
Relay OFF status can be canceled by switching the power OFF.

Low-frequency Load

oscillator LINE SP resistance

. iN
IN Drffere- OUT Attenua- A 1. f. OUT
_I_I_ ntiator tor mp l zer T
Square wave The unit's volume ,
50 Hz, 10v p1) 022301 may 315° be Oscrllo-
' scope
3.3 KG 0.1 [4F 3.3 Kn ( EBVP
IN 10 K 0 0.01 ,u T OUT
7% 151555 X 6
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