Onkyo A 25 Service Manual

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SERIAL NO. 309

ONKYO® SERVICE MANUAL

INTEGRATED DUAL SUPER
SERVO AMPLIFIER
MODEL A-25

TABLE OF CONTENTS

Item Page

Specifications

Service guide

Packing procedures

Exploded View

Component location

PC board View from bottom side

Schematic diagram

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PC board-parts list

ONKYOO
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SPECIFICATIONS

Power Output:

Total Harmonic
Distortion:
IM Distortion:
Damping Factor:
Sensitivity and

Impedance:

Phono Overload:
Bass Control:
Treble Control:
Signal to Noise

40 watts per channel min. RMS,
at 8 ohms both channels driven,
from 20 Hz to 20 kill, with no
more than 0.04% total harmonic
distortion.

0.04% at rated power.

0.04% at rated power.

40 at 8 ohms.

Phono (MM): 25 mV/SO kohms
(MC): 350 uV/330 ohms

Tuner: 150 mV/SO kohms

Tape Play: 150 mV/SO kohms

Tape Rec: 150 mV/l kohms
(Phono)

180 mV RMS at 1 kHz, 0.04% THD
:8 dB at 100 Hz

:8 dB at 10,000 Hz

Phono (MM): 75 dB (IHF A~202,

Ratio 5 mV input, 1 watt
output)

SERVICE GUIDE

1. Replacing the fuse
For continued protection against fire hazard, replace only
with same type and same rating fuse.

(l ) AC fuse

Remove the top cover.

Circuit No. Parts No. Description
120V model

F901 252049 4A(ST-6)
22W model

F901 252074 2A-SE-EAK

F911, F912 252078 5A-SE»EAK

120/220V model
F901 25 2014 4A-T
F902 25 2074 2A-SE-EAK

(2) Speaker protection fuse
Remove the top cover.
F501, F601 252014 4A-T

2. Protective circuit

This model has a built-in thermal switch to protect the
power IC. The thermal switch is not activated under normal
operating conditions.

However, if there is an abnormal rise in the inside tem-
perature, the thermal switch cuts off the outputs.

(The pilot lamp will not turn off.)

When this occurs, wait for a while until the temperature is
cooled down after remove the abnormal conditions.
(Abnormal condition means operation with a load below
4 ohms, or under poor conditions with high power such as a
place with in sufficient air circulation.)

(MC): 66 dB (IHF A-202,
0.5 mV input, 1 watt
output)
Tuner & Tape 80 dB (IHF A-202,
0.5V input, 1 watt
output)

Loudness: +6 dB at 70 Hz
+5 dB at 10 kHz
General
Power Supply: AC 120 V, 60 Hz.
AC 220 V, 50 Hz.
AC 110/220 V, 50/60 Hz.
Semiconductors: 7 ICs, l transistor, 21 diodes,
Dimensions: 418(W) x 83(H) x 280(D) mm
16»1/2"x 3-1/4"x 11"
Weight: 6.5 kg, 14.3 lbs.

Specifications and features are subject to change without
notice.

3. Voltage Selector (Rear Panel)

Some models are equipped with a voltage selector to con-
form with local power supplies.

Be sure to set this switch to match the voltage of the power
supply in your area before turning the power switch on.
Voltage is changed by sliding the groove in the switch with
a screwdriver to the right or left. Confirm that the switch
has been moved all the way to the right or left before turn-
ing the power switch on.

If there is no voltage selector switch on the unit you have
purchased, it can only be used in areas where the power
supply voltage is the same as that of the unit.