Sony KDL-40NX725 Service Manual ▷ View online
KDL-40NX725 4
SECTION 1 - SAFETY AND FEATURES
SPECIAL HANDLING INSTRUCTIONS WHEN REPLACING THE LCD PANEL ASSEMBLY
Use the following precautionary guidelines when handling the LCD Panel Assembly to avoid material degradation or screen coating degradation,
and ensure that dust, dirt, or fingerprints are not left between the glass and the LCD Panel Assembly.
1. After removing the boards and connectors, note where the frame is on the panel. (Figure 1)
2. Lift the LCD Panel Assembly by holding the top and bottom of the panel approximately 200mm from the edge with your palms
on the back of the panel. (Figure 2)
CAUTION: Lifting or holding the panel at the corners may damage the panel.
3. Use the same method when taking the replacement panel out of the carton. (Figure 3)
Figure 1
Figure 2
Figure 3
CAUTION: DO NOT lift the LCD Panel by holding the short side of the panel or by placing your palms on the front glass. (Figures 4 & 5)
Figure 4
Figure 5
KDL-40NX725 5
SECTION 1 - SAFETY AND FEATURES
SAFETY-RELATED WARNINGS
USE CAUTION WHEN HANDLING THE LCD PANEL
When repairing the LCD panel, be sure you are grounded by using a wrist band.
When installing the LCD panel on a wall, the LCD panel must be secured using the 4 mounting holes on the rear cover.
When installing the LCD panel on a wall, the LCD panel must be secured using the 4 mounting holes on the rear cover.
1. Do not press on the panel or frame edge to avoid the risk of electric shock.
2. Do not scratch or press on the panel with any sharp objects.
3. Do not leave the module in high temperatures or in areas of high humidity for an extended period of time.
4. Do not expose the LCD panel to direct sunlight.
5. Avoid contact with water. It may cause a short circuit within the module.
6. Disconnect the AC power when replacing the backlight or inverter circuit.
(High voltage occurs at the inverter circuit at 650Vrms.)
7. Always clean the LCD panel with a soft cloth material.
8. Use care when handling the wires or connectors of the inverter circuit. Damaging the wires may cause a short.
9. Protect the panel from ESD to avoid damaging the electronic circuit (C-MOS).
10. During the repair,
DO NOT leave the Power On for more than 1 hour while the TV is face down on a cloth
.
KDL-40NX725 6
SECTION 1 - SAFETY AND FEATURES
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 antenna terminals, metal trim, “metallized” knobs, screws, and all other exposed metal parts for AC leakage.
Check leakage as described below.
KDL-40NX725 7
SECTION 1 - SAFETY AND FEATURES
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.
4. 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
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
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 B. Checking for earth ground.
To Exposed Metal
Parts on Set
0.15 µF
Earth Ground
AC
Voltmeter
(0.75V)
Figure A. Using an AC voltmeter to check AC leakage.
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