Onkyo TARW 470 Service Manual

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i

SERIAL No. 3301

ONKYO SERVICE MANUAL

STEREO CASSETTE
TAPE DECK

MODEL TA-FIW47O

Black model
UD, UD ® I20v AC, 60Hz
UG 220V AC, SOHZ
UW 120 or 220V AC, 50/6OHZ
UQA, UQB 240V AC, SOHZ
SAFETY-RELATED COMPONENT WARNING SPECIFICATIONS
COMPONENTS IDENTIFIED BY MARK «L ON Track system: racks, 2-channels
THE SCHEMATIC DIAGRAM AND IN THE PARTS Erasing System: AC erase _
LIST ARE CRITICAL FOR RISK OF FIRE AND Tape Speed: 3.: 2mm. ggfi :p:: M h 5 sad (My
ELECTRIC SHOCK. REPLACE THESE COM- bgng, ' 'p' ' 9 "
PONENTS WITH ONKYO PARTS WHOSE PARTS Wow and Flutter: 006% IWRMSI
Frequency Response: 20-15,000Hz INormal)
NUMBERS APPEAR AS SHOWN IN THIS MANUAL. (714900.41 13-d3)
MAKE LEAKAGE-CURRENT OR RESISTANCE fggfé?gg:,:z:3'g'g,
MEASUREMENTS TO DETERMINE THAT 20-179mm (Metal)
EXPOSED PARTS ARE ACCEPTABLY IN- 30-'6-000H1 2363
L f: ' '
SULATED FROM THE SUPPLY CIRCUIT BEFORE 5 33" EflzgeNSdfmfffi 13;§;§§j§,§{fpe
RETURNING THE APPLIANCE TO THE and 5:18 at lkHz is possible with Dolby B
NR. A noise reduction of 20dB at 5kHz is
CUSTOMER possible with Dolby C NR.
Input Jacks: Microphone iack: 1
Input sensitivity: 'lmV/GOO ohms
Input impedance: 5.6 kohms
Line IN: 2
Input sensitivity: GOmV
Input Impedance: 50 kohms
Outputs: Headphone jack: 1
Optimum load impedance: 8 to 200
ohms
Line OUT: 2
Standard output level: 500mV (OdB)
Optimum load impedance: over 50
kohms
Motors: DC servo motor x 2; DC motor x 2
Heads: REC/PB: special hard permalloy x 2;
Erase head: lerrite x 1
Power Supply Rafing: UK and Australian models:
AC 240V, 50Hz

U.S.A. and Canadian models:
AC 120V, 60 Hz

Worldwide models:
I AC 120V and 220V switchable, 50/60Hz
® Power Consumption: 27 watts
Dimensions: 435IW) x 115(HI x 334(Dimm
I I17-1/8"x4-1/2"x13-1/8)
l Weight: 61) k9 I132 lbs.)

Specifications and external appearance are subject to change without
notice because of product improvements.

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TA-RW47O

SERVICE PROCEDURES

1. Replacement of power supply cord

There are two power supply cord outlets on the strainrelief.
Insert them in prescribed direction to ensure safety, AS-UC-
3 (UD<]20V> model) should be inserted lengthwise and
other types of cords should be inserted horizontally.

Power Supply Cord Power Supply Cord

3
length wise Horizontal
direction direction

2. Insulating resistance measurement

Connect the insulating-resistance tester between the plug of
power supply cord and chassis.

Specifications; 500V more than lOMQ

MECHANISM OPERATION

1. Overview of the Cassette Drive Mechanism

The cassette drive mechanism consists of two motors
and one solenoid. It is based on the same principle as
our previous three-motor mechanisms (which employed
separate capstan, reel and assist motors) except that one
motor is used for both the reel and assist functions. The
solenoid is provided to switch between the two functions.
As the mechanism is basically identical to our previous
three-motor configuration except for the reel/assist switch-
ing function, the discussion below will focus on the switch-
ing functions main features.

Reel gear

\- Flight reel

Idler gear

\- Left reel

Figure l: Frontal View of the Assist/Reel Drive Train

In the previous (three-motor) mechanism, the idler
gear had two positions: A for fast forward and C for
rewind. In the new configuration a third position (B) is
added for assist operation.

In the B position, the idler gear is linked to a cam
which raises and lowers the heads and rotates them during
auto-reverse play. To keep the gear firmly in position, a

notched lever presses up against the gear shaft from below.
The gear shaft rests in the notch in the lever, maintaining
the idler gear in the B position. This arrangement makes
it possible to use a single motor for both the reel and assist
functions.

Attraction from the solenoid is used to switch from
the assist position (position B in figure 1 above) to either
the rewind or fast forward position for reel operation.
Attractive force from the solenoid is applied to the notched
lever, pulling it downward. This disengages the gear shaft
from the notch and frees the gear. Then, by applying
voltage to the motor, the idler gear can me moved to
either the A or C position for reel operation. The notched
lever also acts a brake for the reels when solenoidal attrac-
tion is applied.

In order to switch back from reel to assist operation,
the polarity of the voltage being applied to the motor
is reversed. This causes the gear to jerk in the direction of
the opposite reel. When it comes to point B, however,
the gear shaft catches in the notch in the lever, holding
the gear in position for assist operation. This design ensures
that the idler gear always switches initially to the assist
position before switching to another operation. This also
quarantees that the mechanism will be in the correct
position after all operations are completed.

The assist/reel motor uses three different voltages to
perform the operations described above. The approximate
voltages are as follows: 8V for assist operations; 6V for
high-speed fast forward and reverse; and 3.5V for recording
and playback. They are controlled by the TRQl and TR02
signals from the microprocessor. In assist operation, the
idler gear turns clockwise (viewed from the front) during
forward play and counterclockwise during reverse play.

2. Mechanism Drive System

The waveforms which drive the mechanism look rather
complicated on an oscilloscope. If we break them down
into the basic patterns which indicate separate operations,
however, and display the combined result in tabular form,
table 1 is the result. When the operations listed under
Mechanism Operations are performed in the order
specified (i.e. left to right), the operation modules"
listed under Drive Sequence are activated in the order
shown (left to right). Figure 2 through 8 below illustrate
the waveforms for the various modules.

Note: The polarity of the waveforms differs depending on
the direction of tape travel and the type of operation.
All durations are given in milliseconds [ms] .