Sony STR-DE475 Service Manual - Page 3

STR-DE475 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 AC leakage. Check leakage as described below. LEAKAGE 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 microamperes). 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. Follow 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 voltmeter. 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 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 Parts on Set TABLE OF CONTENTS 1. GENERAL 4 2. TEST MODE 6 3. DIAGRAMS 3-1. Circuit Boards Location 8 3-2. Block Diagram Main Section 9 3-3. Block Diagram Display Section 10 3-4. Schematic Diagram Main Section (1/3 11 3-5. Schematic Diagram Main Section (2/3 12 3-6. Schematic Diagram Main Section (3/3 13 3-7. Printed Wiring Board Main Section 14 3-8. Schematic Diagram Digital Section 15 3-9. Printed Wiring Board Digital Section 16 3-10. Schematic Diagram Display Section 17 3-11. Printed Wiring Board Display Section 18 3-12. Schematic Diagram Video Section 19 3-13. Printed Wiring Board Power Section 20 3-14. Printed Wiring Board Video Section 20 3-15. IC Block Diagrams 21 3-16. IC Pin Function Description 23 4. EXPLODED VIEWS 25 5. ELECTRICAL PARTS LIST 27 0.15 µF 1.5 kΩ AC Voltmeter (0.75 V) Earth Ground Fig. A. Using an AC voltmeter to check AC leakage. SAFETY-RELATED COMPONENT WARNING!! COMPONENTS IDENTIFIED BY MARK 0 OR DOTTED LINE WITH MARK 0 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. ATTENTION AU COMPOSANT AYANT RAPPORT À LA SÉCURITÉ! LES COMPOSANTS IDENTIFÉS PAR UNE MARQUE 0 SUR LES DIAGRAMMES SCHÉMATIQUES ET LA LISTE DES PIÈCES SONT CRITIQUES POUR LA SÉCURITÉ DE FONCTIONNEMENT. NE REMPLACER CES COMPOSANTS QUE PAR DES PIÈSES SONY DONT LES NUMÉROS SONT DONNÉS DANS CE MANUEL OU DANS LES SUPPÉMENTS PUBLIÉS PAR SONY. 3