Safety Check Out; Warnings And Cautions - Dell P792 Service Manual

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
touching 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 replacement parts, 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 specifi ed values. Make
sure your instruments are accurate; be suspicious of your HV meter
if sets always have low HV.
8. 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 microamperes). Leakage current
can be measured by any one of three methods.
WARNING!!
NEVER TURN ON THE POWER IN A CONDITION IN WHICH THE
DEGAUSS COIL HAS BEEN REMOVED.
SAFETY REALTED COMPONENT WARNING!!
COMPONENTS IDENTIFIED BY SHADING 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.
SAFETY CHECK-OUT
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 milliampmeter. 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 2 VAC range are suitable (see Figure A).

WARNINGS AND CAUTIONS

NE JAMAIS METTRE SOUS TENSION QUAND LA BOBINE DE
DEMAGNETISATION EST ENLEVEE.
ATTENTION AUX COMPOSANTS RELATIFS A LA SECURITE!!
LES COMPOSANTS IDENTIFIES PAR UNE TRAME ET PAR UNE
MARQUE SUR LES SCHEMAS DE PRINCIPE, LES VUES EXPLOSEES
ET LES LISTES DE PIECES SONT D'UNE IMPORTANCE CRITIQUE
POUR LA SECURITE DU FONCTIONNEMENT. NE LES 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 MANUEL.
SUIVRE CES PROCEDURES LORS DE CHAQUE REMPLACEMENT
DE COMPOSANTS
FONTIONNEMENT SUSPECTE.
— 5 —
To Exposed Metal
Parts on Set
1.5 K Ω
0.15 F
Earth Ground
Figure A. Using an AC voltmeter to check AC leakage.
AVERTISSEMENT!!
CRITIQUES,
P792
AC
Voltmeter
(0.75 V)
OU LORSQU'UN MAUVAIS