Sony KL-W9000 service manual Safety CHECK-OUT

SAFETY CHECK-OUT	KL-W7000/W9000
	RM-Y980
(US Model only)

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 transis- tors, 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 recom- mend 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 condition of the monopole antenna (if any).

Make sure the end is not broken off, and has the plastic cap on it. Point out the danger of impalement on a broken antenna to the customer, and recommend the antenna’s replacement.

8.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.

9.Check the antenna terminals, metal trim, “metallized” knobs, screws, and all other exposed metal parts for AC Leakage. Check leakage as described below.

To Exposed Metal

Parts on Set

AC

0.15 µF1.5 k ΩVoltmeter

(0.75 V)

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 microampers). 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 ex- amples of a passive VOMs that are suitable. Nearly all battery operated digital multimeters that have a 2 V AC range are suit- able. (See Fig. A)

HOW TO FIND A GOOD EARTH GROUND

A cold-water pipe is 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 – 100 watts trouble light (not a neon lamp) between the hot side of the recep- tacle and the retaining screw. Try both slots, if necessary, to locate the hot side of the line, the lamp should light at normal brilliance if the screw is at ground potential. (See Fig. B)

Trouble Light

AC Outlet Box Ohmmeter

Cold-water Pipe

Earth Ground

Fig. A. Using an AC voltmeter to check AC leakage.

Fig. B. Checking for earth ground.

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