Sony MDS-JB920 service manual Section Servicing Notes, Table of Contents, Diagrams

	TABLE OF CONTENTS
1.	SERVICING NOTES	4
2.	GENERAL	11
3.	DISASSEMBLY	14
4.	TEST MODE	18
5.	ELECTRICAL ADJUSTMENTS	23

6.DIAGRAMS

6-1. IC Pin Function Description		32
6-2.	Block Diagram – SERVO Section –	41
6-3.	Block Diagram – MAIN Section –	43
6-4.	Note for Printed Wiring Boards and
	Schematic Diagrams	46
6-5.	Printed Wiring Board – BD Section –	47
6-6.	Schematic Diagram – BD Section (1/2) –	49
6-7.	Schematic Diagram – BD Section (2/2)–	51
6-8.	Schematic Diagram – MAIN Section (1/3)–	55
6-9.	Schematic Diagram – MAIN Section (2/3)–	57
6-10. Schematic Diagram – MAIN Section (3/3)–		59
6-11.	Printed Wiring Board
	– MAIN Board (Side A)	61
6-12.	Printed Wiring Boards
	– MAIN Board (Side B), AC/BAT Boards	63
6-13.	Printed Wiring Boards
	– PANEL Section –	65
6-14. Schematic Diagram – PANEL Section –		67
6-15.	Schematic Diagram
	– BD SWITCH Section –	69
6-16.	Printed Wiring Board
	– BD SWITCH Section –	69
7.	EXPLODED VIEWS	75
8.	ELECTRICAL PARTS LIST	79

SECTION 1

SERVICING NOTES

SAFETY CHECK-OUT

After correcting the original service problem, perform the follow- ing 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.

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” indica- tion is 0.75 V, so analog meters must have an accurate low- voltage scale. The Simpson 250 and Sanwa SH-63Trd are ex- amples of a passive VOM that is suitable. Nearly all battery operated digital multimeters that have a 2 V AC range are suit- able. (See Fig. A)

To Exposed Metal

Parts on Set

0.15 ∝F	1.5 k Ω	AC
		voltmeter
		(0.75 V)

Earth Ground

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

MODEL IDENTIFICATION

— BACK PANEL —

Part No.

4-998-603-1 ¹ AEP and UK models 4-998-603-3 ¹ US model

4-998-603-4 ¹ Canadian model

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