Sony SDM-V72W Service Manual ▷ View online
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SDM-V72W
WARNINGS AND CAUTIONS
CAUTION
Short circuit the anode of the picture tube and the anode cap to the metal chassis, CRT shield, or carbon painted on the CRT, after
removing the anode.
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!!
Apres avoir deconnecte le cap de l’anode, court-circuiter l’anode du tube cathodique et celui de l’anode du cap au chassis metallique
de l’appareil, ou la couche de carbone peinte sur le tube cathodique ou au blindage du tube cathodique.
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.
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SDM-V72W
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 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 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 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.
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).
How to Find a Good Earth Ground
A cold-water pipe is a guaranteed earth ground; the cover-plate
retaining screw on most AC outlet boxes is also at earth ground. If the
retaining screw is to be used as your earth ground, verify that it is at
ground by measuring the resistance between it and a cold-water pipe
with an ohmmeter. The reading should be zero ohms.
If a cold-water pipe is not accessible, connect a 60- to 100-watt
trouble- light (not a neon lamp) between the hot side of the receptacle
and the retaining screw. Try both slots, if necessary, to locate the hot
side on the line; the lamp should light at normal brilliance if the screw
is at ground potential (see Figure B).
Trouble Light
AC Outlet Box
Ohmmeter
Cold-water Pipe
Figure A. Using an AC voltmeter to check AC leakage.
Figure B. Checking for earth ground.
To Exposed Metal
Parts on Set
0.15 µF
1.5 K Ω
AC
Voltmeter
(0.75 V)
Earth Ground
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SDM-V72W
1-1. REAR PANEL REMOVAL
SECTION 1: DISASSEMBLY
1
Gently pull off rear panel.
1
1-2. REAR COVER ASSEMBLY REMOVAL
3
1
4
2
Place the unit face down on a protective sheet
to avoid scratching.
Remove (4) screws (+BVTP 4 x 10)
from the bottom of the rear panel.
Remove (9) screws (+BVTP 3 x 10)
from the sides of the rear panel.
Lift and remove the
rear cover assembly.
1
2
3
4
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SDM-V72W
Unplug the connector.
Remove (1) screw (+BVTP 3 x 10) from H2 Board.
Lift and remove H2 Board.
1
2
2
3
1-3. H2 BOARD REMOVAL
Unplug connectors.
Remove (2) screws (+BVTP 3 x 6) from the D1 Board.
Release the D1 Board from the tabs, then lift to remove .
1
2
2
3
1-4. D1 BOARD REMOVAL
1
3
3
2
1
1
3
2
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