Sony mdp 650 service manual

Page 2

SAFETY CHECK-OUT

After correcting the original service problem, perform the following
safety checks beiore releasing the set to the customer.

Check the area of your repair for unsoldered or
poorly-soldered connections. Check the entire board
surface for solder splashes and bridges.

Check the interboard wiring to ensure that no wires
are "pinched or contact high-wattage resistors.

Look for unauthorized replacement parts, par-
ticularly transistors, that were installed during a
previous repair. Point them out to the customer and
recommend their replacement

Look for parts which, through functioning, show
obvious signs of deterioration. Point them out to the
customer and recommend their replace-ment.

Check the line cord for cracks and abrasion.
Recommend the replacement of any such line cord to
the customer.

Check the B+ voltage to see it is at the values
specified.

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

To Exposed metal
Parts on Set

AC
voltmeter

o. 15oF = 1.5m (0. 75V)

JVW

='-' Earth Ground

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

LEAKAGE TEST

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

1. A commercial leakage tester, such as Simpson 229 or
RCA WT-54OA. Follow the manufactures'
instructions to use these instruments,

2. A battery operated AC milliammerter. 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 0.75V, so analog meters
must have an accurate Iowvoltage 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 3 2V AC range are
suitable, (See Fig. A)

SAFETY-RELATED COMPONENT WARNING

COMPONENTS IDENTIFIED BY MARK A 0R DOTTED
LINE WITH MARK A ON THE SCHEMATIC DIAGRAMS
AND IN THE PARTS LIST ARE CRITICAL T0 SAFE
OPERATION. REPLACE THESE COMPONENTS WITH
SONY PARTS WHOSE PART NUMBERS APPEAR AS
SHOWN IN THIS MANUAL OR IN SUPPLEMENTS PUB-
LISHED BY SONY.

ATTENTION Au COMPOSANT AyANT RAPPORT
A LA sEcumTEI

LES couIPOSANTs IDENTIFIEs PAR UNE MAHOUE A
sun LEs DIAGRAMMES SCHEMATIQUES ET LA LISTE
DES PIECES SONT CRITIQUES POUR LA SECURITE
DE FONCTIONNEMENT. NE REMPLACER CES com-
POSANTS ouE PAR oEs PIECES SONY DONT LEs
NUMEROS SONT DONNEs DANS CE MANUEL ou
DANS LEs SUPPLEMENTS PUBLIEs PAR SONY.