Sony ta e 741 service manual

Page 2

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.

1. A commercial leakage tester, such as the
Simpson 229 or RCA WT-540A. Follow the
manufacturers instructions to use these instru-
ments.

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 volt-
meter. 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 2 V AC range are
suitable. (See Fig. A)

Ta Exposed Metal
Parts on Set

A C
0.15% g 1.5km / voltmeter
T- 1015 w

7 Earth Ground

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

SAFETvvR E LATED COMPONENT WARNI NGI I

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.

TABLE OF CONTENTS
Section m fig;
1- GENERAL ............. .....l.......l. ........ . ......... non-cooc-Iheno3
2. DIAGRAMS

2-1, IC pin Function

22 Block Diagram --
2-3. Circuit Boards Location
24, Semiconductor Lead Layouls ~~~~~~
2-5. Printed Wiring Boards -Main Section-
2.6. Schematic Diagram -Main Section- -
2~7. Schematic Diagram -Display Section-
2-8, Primed Wiring Boards -Display Section- ------------------------ 23

3. EXPLODED VIEWS

3-1. Front PanelSeclion
3-2. Chassis Section

4_ ELECTRICAL PARTS LIST ....................................... 28