Sony tc rx 79 service manual

Page 1

TC-RX79/RX79ES

SERVICE MANUAL us Model

Canadian Model

TC- RX 79ES

AEP Model

TC - RX 79

Dolby noise reduction manufactured under license from
Dolby Laboratories Licensing Corporation.
"DOLBY" and the double-D symbol DD are trademarks of
Dolby Laboratories Licensing Corporation.

Model Name Using Similar Mechanism TC-RX77/RX77ES

T e T ansoort Mechanism Tyne TOM-200R10
SPECIFICATIONS 8 '
Recording system 4-Irack 2»channel stereo xWs
Fast winding time Approx. 90 sec. with Son c-eo ' ' '
. cassette) ( y Line (Rum Sensmvtty 77.5 mV
Bias AC bias (phono laCkS) input impedance 47 k ohms
Heads Erasing head x 1 (territe head) . . . . ,
Playback/Recording head x1 MIcrophone Inputs Sensmvtty (For a 0.25 mV
(LA head) (phone jacks) low-impedance
Motors Capstan motor x 1 (DC servo motor) microphone)
Reel motor x 1 (DC motor)
ASlST (mechanical drive) motor X 1 Outputs
DC
( motor) Line outputs Rated output level 0.32 V ata load
Signal~to-noise ratio (at peak level) (phono jaws) impedance 0f 47
Cassette Type IV Type ll Type l k ohms
(Dolby NR (Sony Metal- (Sony UX-S) (Sony HF-S) Load impedance Over 10 k ohms
OFF) Select)
59 dB 53 dB 56 dB Headphones Output level 0~1 ,25 mW at a
(stereo phone load impedance of
Measured at peak level weighted without NR. The SIN is jack) 32 ohms

improved by about 15 dB at 500 Hz and by about 20 63
about 1 kHz with Dolby-C NFl on. And by 5 dB at 1 kHz and

by 10 dB about 5 kHz with Dolby-B Nn on. Genera

Power requirements

Harmonic distortion RX79ES : 120 V AC, 60Hz (US, Canadian models)

0.4% (with Sony Type I, 150 nWb/m, RX79 : 220V AC, 50/ 60H: (AEP model)
315 Hz, 3rd H.D.) Power consumption 20 W
1.8% (with Sony Type W, 250 rIWb/m, Dimensions Approx. 430 x 123 x 300 mm (w/h/d)
315 Hz, 3rd H.D.) (17 x 47/5 x 11% inches)
Frequency response 3°le NR OFF) including proiecting parts and controls
Type IV cassette 20 20-000 HZ (13 dB, 50) Weight Approx. 4.7 kg (10 lbs 6 02)
(Sony Metal-Select) £83523 Z [:3 (mi-413)
T 9 II cass it Supplied accessory
(ggny (mg)8 9 25 151000 HZ (13 dB, IEC) Audio connecting cords (2)
Type l cassette . . .
(Sony HF-S) 25 - 16,000 Hz (:3 dB, IEC) Design and specifications subject to change Without notice.

STEREO CASSETTE DECK
S ONY.

Page 2

TC - RX79/79 ES

TABLE OF CONTENTS

Section Title Page
Specification .......................................... 1

Model Identification -------
Safety Check-Out .........

1_ GENERAL .......................................... 3
2. DISASSEMBLY ..................................... 4
3.ADJU5TMENTS ..................................... 7
3» 1. Mechanical Adjustment ~~~~~~~~~~~~~~~~~~~~~ 7
3-2. Electrical Adjustment ........................ 7
4. DIAGRAMS
4- 1. Semiconductor Lead Layout ---------------- 11
4-2. Circuit Boards Location ~~~~~~~~~~~~~~~~~~~~ 11
.4-3. IC Block Diagram ......................... 12
4-4. Printed Wiring Boards -------------------- 13
4~5. Schematic Diagram .............. 17
4-6. Block Diagram .............................. 22
5. EXPLODED VIEWS
5-1. Front Panel Section ~~~~~~~~~~~~~~~~~~ 25
5-24 Chassis Section ............................. 25
5-3. Mechanism Section (TCM-ZOORIO) ~~~~~~~~ 27
5-4. Mechanism Section (TCM-ZOORIO) --------- 28
6. ELECTRICAL PARTS LIST ----------------------- 29

MODEL tDENTIFICATION
- Specification Label -
TC- RX79

TC- RX7QES

MODEL NOl

STEREO CASS ETTE DECK

WW

SERIAL No.
MADE IN JAPAN

US, Canadian Model: AC: 120V 60Hz 30W
AEP Models: AC: 220 - 230V~50I60 Hz

SAFETV-RELATED COMPONENT WARNING

COMPONENTS IDENTIFIED BY MARK A OR DOTTED
LINE WITH MARK A ON THE SCHEMATIC DIAGRAMS
AND IN THE PARTS LIST ARE CRITICAL TO SAFE
OPERATION. REPLACE THESE COMPONENTS WITH
SONY PARTS WHOSE PART NUMBERS APPEAR AS
SHOWN IN THIS MANUAL OR IN SUPPLEMENTS PUB-
LISHED BY SONY.

SAFETY CHECK-OUT

After correcting the original service problem,
perform the following safety check before releasing
the set to the customer:

Check the antenna terminals, metal trim, metallized
knobs, screws, and all other exposed metal parts for
AC leakage. Check leakage as described below.

LEAKAGE TEST

The AC leakage from any exposed metal part to
earth ground and from all exposed metal parts to any
exposed metal part having a return to chassis, must
not exceed 0.5 mA (500 microampers). Leakage
current can be measured by any one of three
methods.

I. A commercial leakage tester, such the
Simpson 229 or RCA WT-S4OA. Follow the
manufacturers instructions to use these instru-

(AS

ments.

2. A battery-operated AC milliammeter. The Data
Precision 245 digital multimeter is snitablc for
this job.

3. Measuring the voltage drop across a resistor by

means of a VOM or battery-operated AC volt:
meter. The limit indication is 0.75V, so
analog meters must have an accurate low-
voltage scale. The Simpson 250 and Sanwa
SH-63Trd are examples of a passive VOM that
is suitable. Nearly all battery operated digital
multimeters that have a 2V AC range are
suitable. (See Fig. A)

To Exposed Metal
Part: on Se!

fl
{gm/dz J

._I

A C
voltmeter
(0.75 V}

0.75uF

Earth Ground

Fig. A. Using an AC voltmeter to check AC leakage.

ATTENTION AU. COMPOSANT AYANT RAPPORT
A LA SECURITE!

LES COMPOSANTS lDENTIFIES PAR UNE MAROUE A
sun LES DIAGRAMMES SCHEMATIQUES ET LA 1.1er
DES PIECES sour camoues POUR LA sécumré
DE FONCTIONNEMENT. NE REMPLACER CES COM-
POSANTS ous PAR DES PIECES sonv DONT LES
NUMEROS sour oonwés DANS CE MANUEL ou
DANS LES SUPPLEMENTS PUBLIES PAR SONY.