Safety Check-Out; Leakage Test - Sony AC-V500 Service Manual

AC-V500
SAFETY CHECK-OUT
| 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 splasher and bridges.
2. Check the interboard wiring to ensure that no wires
e "pinched" or contact high-wattage resistors.
3. Look for unauthorized replacement parts, particularly transis-.
tors, that were installed during a previous repair. Point them
out to the customer and recommend their replacement.
4. Look for parts which, though functioning, show obvious signs
of deterioration. Point them out to the customer and recom-
mend their replacement.
5. 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
___] (0.78v)
0.15uF
Earth Ground
Fig. A. Using an AC voltmeter to check AC leakage.
SAFETY-RELATED COMPONENT WARNING!!
COMPONENTS IDENTIFIED BY SHADING AND MARK A\ ON
THE. SCHEMATIC DIAGRAMS, EXPLODED VIEWS 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 PUBLISHED BY SONY. CIRCUIT ADJUST-
MENTS THAT ARE CRITICAL TO SAFE OPERATION ARE IDENTIFIED
IN THIS MANUAL. FOLLOW THESE PROCEDURES WHEN-
EVER CRITICAL COMPONENTS ARE REPLACED OR IMPROPER
OPERATION IS SUSPECTED.
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 0.5mA (500 microampers).
Leakage current can be measured by any one of three methods.
1. Acommercial 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 0.75V, 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 2V AC range are
suitable. (See Fig.A)
ATTENTION AU COMPOSANT AYANT RAPPORT
A LA SECURITE!!
LES COMPOSANTS IDENTIFIES PAR UN TRAME ET UNE
MARQUE A SUR LES DIAGRAMMES SCHEMATIQUES, LES
VUES EXPLOSEES ET LA LISTE DES PIECES SONT CRI-
TIQUES POUR LA SECURITE DE FONCTIONNEMENT. NE REMPLACER
CES COMPOSANTS QUE PAR DES PIECES SONY DONT LES
NUMEROS SONT DONNES DANS CE MANUEL OU DES SUP-
PLEMENTS PUBLIES PAR SONY. LES REGLAGES DU CIR-
'CUIT QUI SONT CRITIQUES POUR LA SECURITE DE FONCT [ONNEMENT
SONT IDENTIFIES DANS CE MANUEL. SUIVRE LES PROCEDURES
QUAND LES COMPOSANTS CRITIQUES SONT REMPLACES
OU LE FONCTIONNEMENT IMPROPRE EST SUSPECTE.