Sony STSA-50-ES Service manual

ST-SA50ES

SERVICE MANUAL

SPECIFICATIONS

FM tuner section

Frequency range 87.5 – 108.0 MHz Antenna terminals 75 Ω, unbalanced Intermediate frequency 10.7 MHz Sensitivity at 26 dB quieting

(mono) 10.3 dBf, 0.9 µV/75 Ω

at 46 dB quieting

(stereo) 38.5 dBf, 23 µV/75 Ω

Usable sensitivity (IHF) 10.3 dBf, 0.9 µV/75 Ω S/N at 40 kHz deviation

95 dB (mono), 86 dB (stereo)

Harmonic distortion WIDE

0.008 % (mono), 0.02 % (stereo)

NARROW

0.04 % (mono), 0.07 % (stereo)

Frequency response 15 Hz – 15 kHz

(±0.2 dB) Separation 65 dB at 1 kHz Selectivity at 400 kHz

WIDE 80 dB NARROW 90 dB

at 300 kHz

WIDE 45 dB NARROW 70 dB

Output at 40 kHz deviation 600 mV

US Model

AM tuner section

Frequency range AM :530 – 1,710 kHz (10 kHz step) Intermediate frequency 450 kHz Usable sensitivity (with AM loop antenna)

200 µV/m

Signal-to-noise ratio AM :54 dB (50 mV/m, 1,050 kHz) Harmonic distortion 0.3% (50 mV/m, 400 Hz) Selectivity 50 dB

General

Power requirements 120 V, AC 60 Hz Power consumption 13 W Dimensions 16 15/16 × 3 7/8 × 13 3/8 in.

(430 × 98 × 340 mm)

Weight 9 lbs. 1 oz.(4.1 kg) Supplied accessories Audio cord (1)

AM loop antenna (1) FM wire antenna (1) Antenna adapter (1)

Design and specifications are subject to change without notice.

MICROFILM

FM STEREO FM-AM TUNER

TABLE OF CONTENTS

1. GENERAL............................................................................3

2. DISASSEMBLY

2-1. Panel, Front Assembly........................................................ 4

2-2. Display Board, Encoder Board, AC SW Board.................. 4

2-3. Panel Front ......................................................................... 4

3. TEST MODE........................................................................ 5

4. ELECTRICAL ADJUSTMENTS................................... 7

5. DIAGRAMS

5-1. Circuit Boards Location ................................................... 11

5-2. Printed Wiring Board – Display Section – ....................... 13

5-3. Schematic Diagram – Display Section – .......................... 15

5-4. Printed Wiring Board – Tuner Section – .......................... 17

5-5. Schematic Diagram – Tuner Section (1/2)– ..................... 19

5-6. Schematic Diagram – Tuner Section (2/2)– ..................... 21

5-7. IC Pin Function ................................................................ 23

5-8. IC Block Diagrams ........................................................... 24

6. EXPLODED VIEW

6-1. Front Panel and Case Section ........................................... 25

7. ELECTRICAL PARTS LIST......................................... 26

SAFETY CHECK-OUT

After correcting the original service problem, perform the following safety checks before releasing the set to the customer: Check the antenna terminals, metal trim, “metallized” knobs, screws, and all other exposed metal parts for A C leakage. Check leakage as described below.

LEAKAGE

The A C leakag e 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.

1. A commercial leakage tester, such as the Simpson 229 or RCA WT -540A. Follo w the manufacturers’ instructions to use these instruments.

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

3. Measuring the voltage drop across a resistor by means of a VOM or battery-operated AC v oltmeter . The “limit” indication is 0.75 V, so analog meters must have an accurate low-voltage scale. The Simpson 250 and Sanwa SH-63Trd are e xamples 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 Parts on Set

0.15µF

1.5k

Ω

voltmeter (0.75V)

Earth Ground

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

SAFETY-RELATED COMPONENT WARNING!!

COMPONENTS IDENTIFIED BY MARK ! OR DO TTED LINE WITH MARK ! 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 PUBLISHED BY SONY.

— 2 —

Location of Controls

SECTION 1

GENERAL

1 POWER swtich (U) 2 DISPLAY button 3 ANTENNA button 4 ASM button 5 ANT ATT button 6 IF BAND button 7 FM MODE button 8 BAND button 9 MEMORY button

0 CHARACTER button !¡ MENU button !™ RETURN button !£ TUNE MODE button !¢ TUNING/SELECT knob !∞ ENTER button !§ NUMBER buttons !¶ SHIFT button

— 3 —

SECTION 2

DISASSEMBLY

Note : Follow the disassembly procedure in the numerical order given.

2-1. PANEL, FRONT ASSEMBLY

Panel, front assembly

Three screws

(BV3

Connector

(CNP701:TUNER board)

Connector

(CNP702:TUNER board)

Connector

(CNP951:TUNER board)

Lead with connecto

Remove the two claws by pressing them in the direction of the arrow.

2-2. DISPLAY BOARD, ENCODER BOARD,

AC SW BOARD

T wo screws

(BV3

DISPLAY board

Nut supplied

with RV701

Knob (T)

AC SW board

Remove the

five claws.

Loosen the screw.

Four screws

(BV3

ENCODER board

2-3. PANEL, FRONT

While pressing the three claws in the direction of the arrow, pull the top of the panel slightly.

Panel, front

Remove the two lower claws in the direction of the arrow.

— 4 —

SECTION 3

TEST MODE

1. Circuit Check Mode

1. Turn OFF the power.

2. While pressing 4 and MENU together, turn ON POWER .

• The items in the following table will be checked automatically in order every 2 seconds.

Display

Tuned IF Frq

Sig Level

Stereo

Items

AST signal = LOW

IF COUNT OK

SI LEVEL > 70dB

ST signal = LOW

FM RDS OK or NG OK or NG

OK or NG

DISPLAY

OK or NG OK or NG

IC251 NG, RV251 adjustments

FE101, IC251 NG, or IF count buffer amp (Q251, Q401) NG

IC221 NG, RV221 adjustments IC301 NG, RV301 adjustments

— 5 —

NOTE : The preset data will be erased when this test mode is used. Therefore, take do wn the data before setting this mode and preset the data

again after completing operations in this mode.

2. Display Tube Check and KEY Check mode

NOTE : Do not perform this check mode when replacing display tubes or excepting when replacing a microcomputer.

1. Turn OFF the power.

2. While pressing 1 and MENU together, turn ON POWER .

3. While continuously pressing 1 and MENU together, check the following.

Microcomputer version indication (1 sec) All light up “7F” Dot area only “60” Dot area only “7E”

Dot area only “3D”Dot area only “5F”

Indication test pattern

1 7F 2 60 3 7E 4 3D 5 5F

* The indication test patterns from 2 to 5 are indicated on only even grids.

The display changes every 1 sec.

4. Release 1 and MENU . The KEY CHECK mode will be set.

5. All key numbers will be displayed. Key Number : 24

6. Each time the key is pressed, the key number will be counted down.

Each key will be counted only once, at the first time.

7. When all keys have been pressed, the process will end.

NOTE : As contents of the Factory Preset will be written into memory after completing this check mode, delete contents of memory

according to 4. Forced RESET.

3. Entering the Factory Preset (In case perform just to write memory of the Factory Preset.)

1. Turn OFF the power.

2. While pressing 3 and MENU together, turn ON POWER .

4. Forced RESET (Used to delete the contents of Factory Preset when it is written into the preset memory .)

Clears all the RAMs and sets the initial state

1. Turn OFF the power.

2. While pressing 5 and MENU together, turn ON POWER .

5. How to select the frequency steps of the AM band

1. 9kHz step : while pressing 9 , turn ON POWER .

2. 10kHz step : while pressing 0 , turn ON POWER .

— 6 —

SECTION 4

)

ELECTRICAL ADJUSTMENTS

Precautions in Repairing

If the front end unit fails, it is difficult to repair the inner circuits, so replace the entire front end unit.

FM SECTION 0dB = 1µV

FM RF Stereo signal generator

set

FM ANTENNA (75Ω)

• Standard Setting of FM Stereo RF Signal Generator.

STEREO STANDARD SIGNAL

Carrier frequency : 98MHz Modulation : Audio 1kHz Main channel (L+R) : 33.75kHz

deviation

Sub channel (L–R) : 33.75kHz

deviation

Pilot : 7.5kHz

Deviation

1kHz highpass filter

LINE OUT

STANDARD SIGNAL

Carrier frequency:98MHz Modulation :Audio 1kHz

distortion mete

MONAURAL

75kHz deviation

FM Discriminator ADJUSTMENT (NULL and MONO Distortion Adjustment)

Setting:

IF BAND : WIDE

FM RF Stereo signal generator

set

FM ANTENNA (75Ω)

Ω

open)

(at 75

Modulation : Monaural Standard signal Output level : 6mV (76dB

TP251 NULL terminal

)

VTVM (DC range

1kHz highpass filter

LINE OUT

distortion mete

Procedure:

1. Tune the set to 98 MHz.

2. Adjust T252 for 0V reading on the VTVM.

................... NULL

3. Adjust T253 for a minimum reading on the distortion meter.

................... MONO Distortion (THD)

4. Repeat the adjustments of 2 and 3 several times.

Note : When replacing the ceramic filter, perform this alignment.

— 7 —

Front End IFT/STEREO Distortion Rate Adjustment

Setting:

IF BAND : WIDE

FM RF Stereo signal generator

Oscilloscop

Stereo Level Adjustment

Setting:

IF BAND : WIDE

FM RF Stereo signal generator

1kHz

filter

+ –

distortion mete

set

FM ANTENNA (75Ω) LINE OUT

Modulation : Monaural Standard signal Output level : 2.2µV (7dBµ) (at 75 Ω open)

FM RF Stereo signal generator

highpass

set

FM ANTENNA (75Ω) LINE OUT

Modulation : Stereo Standard signal Output level : 6mV (76dBµ) (at 75 Ω open)

Procedure:

1. Tune the set to 98 MHz.

2. Remove the top cover of the front end (FE101).

3. Adjust IFT1 of the front end (FE101) to put the noise up-anddown and symmetrically on the waveform of the oscilloscope.

4. Adjust the front end (FE101) IFT1 to minimize the STEREO distortion rate.

5. Attach the removed top cover of the front end (FE101) as it was.

Note : Do not turn more than a half turn from the core position

which is adjusted on the front end IFT adjustment.

Narrow THD Adjustment

Setting:

IF BAND : NARROW

FM RF Stereo signal generator

set

1kHz

highpass

filter

distortion mete

set

FM ANTENNA (75Ω)

Modulation : Stereo Standard signal Output level : 32µV (30dBµ) (at 75 Ω open)

Procedure:

1. Tune the set to 98 MHz.

2. Adjust RV251 so that the “STEREO” indicator goes on.

Narrow Gain Adjustment

Setting:

IF BAND : NARROW

FM RF Stereo signal generator

set

FM ANTENNA (75Ω)

Modulation : Stereo Standard signal Output level : 32

V (30dBµ) (at 75 Ω open)

Procedure:

1. Tune the set to 98 MHz.

2. Set IF BAND switch to the NARROW position.

3. Adjust RV231 so that the “STEREO” indicator goes on.

FM Meter Level Adjustment

Setting:

IF BAND : WIDE

FM RF Stereo signal generator

set

FM ANTENNA (75Ω)

FM ANTENNA (75Ω) LINE OUT

Modulation : Stereo Standard signal Output level :6mV (76dBµ) (at 75 Ω open)

Procedure:

1. Tune the set to 98 MHz.

2. Set IF BAND switch to the NARROW position.

3. Set SSG output level to 80dBµ.

4. Adjust RV232 for a minimum reading on the distortion meter.

Modulation : Stereo Standard signal Output level : 3mV (76dBµ) (at 75 Ω open)

Procedure:

1. Tune the set to 98 MHz.

2. Press DISPLAY key to display the digital signal, then adjust RV221 to be displayed as “SIG 70dB”.

— 8 —

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