KDL-42W650A - Sony TV Service Manual (repair manual). Page 4

KDL-42W650A iii

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 in “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.  

Follow the manufacturers’ instructions provided with the tester.

2.  A battery-operated AC milliammeter. 

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. Nearly all 
battery-operated digital multimeters that have a 2 VAC range are 
suitable. (see Figure A)

Figure A. Use an AC voltmeter to check AC leakage.

The cover-plate retaining screw on most AC outlet boxes is at earth ground. 
Verify the AC outlet box retaining screw ground by connecting a 60W to 

100W incandescent (not a neon or fluorescent 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)

Figure B. Checking for earth ground.

Trouble Light

AC Outlet Box