Sony Trinitron CPD-420GS Service Manual page 3

After correcting the original service problem,
perform the following safety checks before releasing the
set to the customer:
1. Check the area of your repair for unsoldered or
poorly-soldered connections. Check the entire
board surface for solder splashes and bridges.
2. Check the interboard wiring to ensure that no wires
are "pinched" or contact high-wattage resistors.
3. Check that all control knobs, shields, covers,
ground straps, and mounting hardware have been
replaced. Be absolutely certain that you have
replaced all the insulators.
4. Look for unauthorized
particularly transistors, that were installed during a
previous repair. Point them out to the customer and
recommend their replacement.
5. Look for parts which, though functioning, show
obvious signs of deterioration. Point them out to
the customer and recommend their replacement.
6. Check the line cords for cracks and abrasion.
Recommend the replacement of any such line cord
to the customer.
7. Check the B+ and HV to see if they are specified
values. Make sure your instruments are accurate;
be suspicious of your HV meter if sets always have
low HV.
8. Check the antenna
"metallized" knobs, screws, and all other exposed
metal parts for AC leakage.
described next.
To Exposed Metal
Parts on Set
0.15 µF
Fig A
SAFETY CHECK-OUT
replacement parts,
terminals, metal trim,
Check leakage as
AC
1.5 k W Voltmeter
(0.75 V)
Earth Ground
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 microampere). 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 instructions.
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's 250 and Sanwa SH-63Trd are examples
of passive VOMs that are suitable. Nearly all
battery operated digital multimeters that have a 2V
AC range are suitable. (See Fig. A)
NEVER TURN ON THE POWER IN A CONDITION IN
WHICH THE DEGAUSS COIL HAS BEEN REMOVED.
SAFETY-RELATED COMPONENT WARNING!!
COMPONENTS IDENTIFIED BY SHADING AND MARK
ON THE SCHEMATIC DIAGRAMS, EXPLODED VIEWS
AND IN THE PARTS LIST ARE CRITICAL FOR SAFE
OPERATION. REPLACE THESE COMPONENTS WITH
SONY PARTS WHOSE PART NUMBERS APPEAR AS
SHOWN IN THIS MANUAL OR IN SUPPLEMENTS
PUBLISHED BY SONY. CIRCUIT ADJUSTMENTS THAT
ARE CRITICAL FOR SAFE OPERATION ARE IDENTIFIED
IN THIS MANUAL. FOLLOW THESE PROCEDURES
WHENEVER CRITICAL COMPONENTS ARE REPLACED
OR IMPROPER OPERATION IS SUSPECTED.
AVERTISSEMENT!!
NE JAMAIS METTRE SOUS TENSION QUAND LA
BOBINE DE DEMAGNETISATION EST ENLEVEE.
ATTENTION AUX COMPOSANTS RELATIFS A LA
LES COMPOSANTS IDENTIFIES PAR UNE TRAME ET
PAR UNE MARQUE
PRINCIPE, LES VUES EXPLOSEES ET LES LISTES DE
PIECES SONT D'UNE IMPORTANCE CRITIQUE POUR
LA SECURITE DU FONCTIONNEMENT.
REMPLACER QUE PAR DES COMPOSANTS SONY
DONT LE NUMERO DE PIECE EST INDIQUE DANS LE
PRESENT MANUEL OU DANS DES SUPPLEMENTS
PUBLIES PAR SONY. LES REGLAGES DE CIRCUIT
DONT L'IMPORTANCE EST CRITIQUE POUR LA
SECURITE DU FONCTIONNEMENT SONT IDENTIFIES
DANS LE PRESENT
PROCEDURES LORS DE CHAQUE REMPLACEMENT
DE COMPOSANTS
MAUVAIS FONTIONNEMENT SUSPECTE.
—3—
CPD-420GS/GST
WARNING!!
SECURITE!!
SUR LES SCHEMAS DE
NE LES
MANUEL. SUIVRE
CRITIQUES, OU LORSQU'UN
CES