Onkyo T 401 Service Manual

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T-401

Ref. No. 3416

ONKYO SERVICE MANUAL

SYNTHESIZED
FM STEREO/AM TUNER

MODEL T-401

Black and Silver models

BHMDN, BHMD 120V AC. 60 Hz
BHMP, MP 230V AC, SOHZ
BHMW l20/220V AC, 50/60Hz
BHMQA 240V AC, 50 Hz

SAFETY-RELATED COMPONENT WARNING
COMPONENTS IDENTIFIED BY MARK A ON
THE SCHEMATIC DIAGRAM AND IN THE PARTS
LIST ARE CRITICAL FOR RISK OF FIRE AND
ELECTRIC SHOCK. REPLACE THESE COMPO-
NENTS WITH ONKYO PARTS WHOSE PART
NUMBERS APPEAR AS SHOWN IN THIS
MANUAL.

MAKE LEAKAGECURRENT OR RESISTANCE
MEASUREMENTS TO DETERMINE THAT EXPOSED
PARTS ARE ACCEPTABLY INSULATED FROM
THE SUPPLY CIRCUIT BEFORE RETURNING

THE APPLIANCE TO THE CUSTOMER.

TABLE OF CONTENTS

Specifications ......
Service procedures
Block diagram ..
Exploded view
Parts list ..........
Block diagram of IC
Packing View ..........
Adjustment procedures
Pc board view/parts list
Main circuit ..
Display/Operation swrtc
Schematic diagram ..
[20V model ..
Other models

1 ONKYO
Alllllll BIIMPIIIIIIIIS

_1_

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SPECIFICATIONS

Tuning Range:

87.9-IO7.9MH2(200kHz steps: U.S.A model)

87.5-108.0Ml-Iz(50kHz steps: European model)
87.9-IU7.9MHZ(200kHz steps) or
87.5-108.0MH2(50kHz steps) (Worldwide model)
Mono: ILZdBf. 1.0 11V IHF

0.9 IV 7Sohms DIN
Stereo: 2.0 FV 7Sohms
Mono: 11.2dBf. 2.0 IV IHF (120V model)
Stereo: 17.2dBf. 4.0 #V (120V model)
Mono: 1.7 #V 7Sohms
Stereo: 1.7 #V 7Sohms
Mono: 16.ldBf. 3.5 11V (120V model)
Stereo: 36.1dBf, 35 #V (120V model)
1.5dB
40dB (120V model)
80dB (Other models)

Usable Sensitivity:

SOdB Quietiug Sensitivity:

Capture Ratio:
Image Rejection Ratio:

IF Rejection Ratio: 90dB
Signal-to-Noise Ratio: Mono: 73dB
Stereo: 66dB

Alternate Channel
Attenuation:

Selectivity:

AM suppression Ratio:

SERVICE PROCEDURES

1. Safety-check out
(Only U.S.A. model)
After correcting the original service problemperform
the following safety check before releasing the set to
the customer.
Connect the insulating-resistance tester between the
plug of power suuply cord and chassis.

50m; IHF (inkHz) (1qu model)

SOdB

Specifications: 3.3Mohm 110% at 500V.

2. Memroy preservation
This unit does not require memory preservation batteries.
A builtin memory power backup system preserves contents
of the memory during power failures and even when the
unit is unplugged The unit must be plugged in and the
power switch turned on and off once in order to charge the
backrup system. Note that since this is not a permanent
memory,the power switch must he turned on and off a few
times each month to keep the back-up system operative.
The period of time during which memory contents are
preserved after power has last been turned off varies
depending on climate and placement of the unit.
0n the average, memory contents are protected over a
period of 3 to 4 weeks (a minimum of 2 weeks) after
the last time power has been turned off. This period is
shorter when the unit is exposed to very high humidity or
used in an area with an extremely humid climate.

3. Voltage Selector (Back Panel)
W 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. This switch is set to
220V at the factory. 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 turning the power switch on.
Models without a voltage selector can only be used in
areas where the power supply is the same as that of the

unit.

SSdB DIN (i300kI-lz, 40kHz dev.) (Other models)

Total Harmonic Distortion: Mono: 0.1%

Stereo: 0.2%
Frequency Response: 30-15, OOOHZ $1.5M)
Stereo Separation: 40dB at lkI-Iz

30:13 at 70 Muting Level: 2.0 l V, 7Sohm

l7.2dBf. 4.0/V

Output Voltage: SOOmV (120V model)
750mV (Other models)
AM:

Tuning Range: 53071710kIIz(IOkHz steps) (U.S.A. model)
522~1fsllkHz( 9H2 steps) (European model)
530-1620kHz(10kHz steps) or

531-1602kHz( 9kHz steps) (Worldwide model)

Usable Sensitivity: 25 F V
Image Rejection Ratio: 40dB
IF Rejection Ratio: 40d];
Signal-to-Noise Ratio: 40dB
Harmonic Distortion: 0.8%
Output voltage: ISOmV

GENERAL:

Dimensions(W>

17-15/16 X 2'15/16 x 12-1/16
Weight: 3.4kg.. 7.5 lbs.
Specifications and features are subject to change without notice.

4. Tuning Step Frequency Switch (Back Panel)
W models are equipped with a switch for the AM (9kHz/
lOkHz) and FM (SOkHz/lOOkI-Iz) bands. The switch
should be set to the proper steps for the radio broadcast
frequencies in your area.

5. Changing the band step
With the exception of the models below, a BAND STEP
selector switch is not provided.

FM
MODEL BAND STEP .1273
UD 200kHz-> SOkI-Iz Open
UP /UQ 50kHz-> ZOUkHz Short
AM
MODEL BAND STEP J238
UD IOkHz a 9kHz Short
U P/UQ 9kHz->10kH2 Open
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Q751
E microprocessor
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1233
____l-L-__
DISPLAY CIRCUIT PCB

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EXPLODED VIEW