Sony DHC-FL3 / GDM-C520 / GDM-C520K / HCD-FL3 Service Manual ▷ View online
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GDM-C520/C520K
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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GDM-C520/C520K
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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GDM-C520/C520K
SECTION 1: DISASSEMBLY
1-1. CABINET REMOVAL
1
Two screws
(+BVTP 4 x 16)
(+BVTP 4 x 16)
6
Slide the EMI shield in the direction
of arrow and remove four claws.
of arrow and remove four claws.
7
EMI shield
4
Four screws
(+BVTT 4 x 8)
(+BVTT 4 x 8)
5
Five screws
(+BVTT 4 x 8)
(+BVTT 4 x 8)
2
Two claws
Bezel
Bezel
EMI shield
Cabinet assembly
Cabinet assembly
Push in the tip of a screwdriver
about 10mm to unlock the claw.
about 10mm to unlock the claw.
B
A
C
3
Push the upper side of the cabinet assembly
in the direction of arrow , disconnect claws,
then remove the cabinet assembly
lifting it up in the direction of arrow .
in the direction of arrow , disconnect claws,
then remove the cabinet assembly
lifting it up in the direction of arrow .
C
B
A
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GDM-C520/C520K
1-2. SERVICE POSITION
1
2
4
1
Remove the D board.
D board
2
Remove the Video block assembly.
3
Install the Adaptor board
(XT MOUNT) (A-1391-123-A).
(XT MOUNT) (A-1391-123-A).
4
Lay the Video block assembly.
Video block assembly
3
Video block assembly
5
Install the video block assembly.
6
Put a box which is about 15cm in height
under the D board to fix it.
(Please disconnect the CN 701 first.)
under the D board to fix it.
(Please disconnect the CN 701 first.)
D board
Box
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