Onkyo T 404 Service Manual

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14

Ref. No 3427

ONKYO SERVICE MANUAL

SYNTH ESIZED
FM STEREO/AM TUNER

MODEL T-404

Black and Silver models

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

SAFETY-RELATED COMPONENT WARNING! I
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
Pans list ...........
BIock diagram of IC .
Packing View ...........
Admstmem procedures
Pc board view/parts list
Main circuit
Display/Operation switch .
Schematic diagram
120V model
Other models ...................

l ONKYO
Alllllll IIIIMPIIIIIIIIS

_1_

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SPECIFICATIONS

87.9»107.9MHZ(200ItHz steps: USA model)
87.5»l08.0MHz(50kl-lz steps: European model)
87.9-107.9Ml{z(200kHz steps) or

Tuning Range:

87.5-108.0MHZ(5(lkHz steps) (Worldwide model)

Usable Sensitivity: Mono: 11.2dBf, 1.0 #V IHF

0.9 l V 750th DIN
Stereo: 20 l V 7Sohms
Mono: Il.2dBf, 2.0 IV IHF (120V model)
Stereo: 17.2dBf. 4.0 FV (120V model)
Mono: 1.7 #V 750th
Stereo: 1.7 #V 7Sohms
Mono: 16,1dBf. 3.5 IV (120V model)
Stereo: 36.1dBf. 35 V (120V model)
l,SdB
40dB (120V model)
2mm (Other models)

50dB Ouicting Sensitivity:

Capture Ratio:
Image Rejection Ratio:

IF Rejection Ratio: 91MB
Signal-to-Noise Ratio: Mono: 73dB
Stereo: 66dB

Alternate Channel
Attenuation:

Seleclivity:

AM suppression Ratio:

SERVICE PROCEDURES

1. Safety~check out
(Only U.S.A. model)
After correcting the original service problem,perforrn
the following safety check before releasing the set to
the customer:
Connect the insulatingwesistance tester between the

SOdB [HF (140mm) (120V model)

50dB

55dB DIN (1300kHz. 40kHz dev.) (Other models)

Total Harmonic Distortion: Mono: 0.1%

Frequency Response:
Stereo Separation:

Muting Level:
Output Voltage:

AM:
Tuning Range:

Usable Sensitivny:
Image Rejection Ratio:
[F Rejection Ratio:
Signal-to-Noise Ratio:
Harmonic Distortion:
Output voltage:
GENERAL:
Dimensions(W X H x D):

Weight:

Stereo: 0.2%
30715.000H1 11.5dB
40dB at lkHz

30dB at 70-10.000Hz
20 #V. 7Sohm
17.2dBf, 4.0/1 V
SOflmV (120V model)
750mV (Other models)

SMHHOkHzthkHz steps) (USA. model)
522»161lkHz( 9H2 steps) (European model)
53411620kHz(10kHz steps) or

531-1602kHz( okllz steps) (Worldwide model)
25 l V

40dB

40dB

40dB

0.8%

lSOmV

455 x 75.5 X 306mm
I7-15/16" X 2-15/16" X lZ-l/lél"
3,4kg 7.5 lbs.

Specifications and features are subject to change without notice.

plug of power suuply cord and chassis,

Specifications: 3.3Mohm :1096 at 500V.

2. Memroy preservation

This unit does not require memory preservation batteries.

A bullkin 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
backup system. Note that since this is not a permanent
memory.the power switch must be turned on and off a few
times each month to keep the backup 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.

. 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 ofthe
Lin".

4. Tuning Step Frequency Switch (Back Panel)
W models are equipped with a switch for the AM (9kHz/
lOkI-lz) and FM (SOkHz/ZOOkHz) 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 BANDSTEP J243
UD 2(lflkHz a 50k Hz Open
UP/UQ 50kllz-> 200kHz Short
AM
MODEL BAND STEP 1246
U0 l()kI-lz -> 9kHz Short
UP/UQ 9kHZ->10kHz Open
_l-l_,_l-
Q751
5 microprocessor
_ I a
1246
_._l-L__
DISPLAY ClRCUlT PCB