Sony KLV-21SG2 Service Manual page 3

SAFETY CHECK-OUT
After correcting the original service problem, perform the fol-
lowing safety checks before releasing the set to the customer:
1. Check the area of your repair for unsoldered or poorly-sol-
dered 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 replacement parts, particularly tran-
sistors, 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 terminals, metal trim, "metallized"
knobs, screws, and all other exposed metal parts for AC
Leakage. Check leakage as described right.
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.
1. A commercial 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 0.75 V, so analog meters must have an accurate low-
voltage scale. The Simpson 250 and Sanwa SH-63Trd are
examples of a passive VOMs that are suitable. Nearly all
battery operated digital multimeters that have a 2 V AC
range are suitable. (See Fig. A)
To Exposed Metal
Parts on Set
0.15 µF
Fig. A. Using an AC voltmeter to check AC leakage.
AC
1.5 k Ω
Voltmeter
(0.75 V)
Earth Ground
CAUTION
These servicing instructions are for use by qualified service
personnel only. To reduce the risk of electric shock, do
not perform any servicing other than that contained in the
operating instructions unless you are qualified to do so.
WARNING!!
An isolation transformer should be used during any service
to avoid possible shock hazard, because of live chassis. The
chassis of this receiver is directly connected to the ac power
line.
!
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.
ATTENTION!!
Ces instructions de service sont à l'usage du personnel de
service qualifié seulement. Pour prévenir le risque de choc
électrique, ne pas faire l'entretien autre que celui contenu
dans le Mode d'emploi à moins que vous soyez qualifié faire
ainsi.
Afin d'eviter tout risque d'electrocution provenant d'un
chássis sous tension, un transformateur d'isolement doit etre
utilisé lors de tout dépannage. Le chássis de ce récepteur
est directement raccordé à l'alimentation du secteur.
!
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 critiques, ou lorsqu'un
mauvais fonctionnement suspecte.
KLV-21SG2 (UC) 3