Sony INT-W200 Service Manual page 2

INT-W200 / INT-WJ200
After correcting the original service problem, perform the following safety checks before releasing the unit 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 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 transistors, that were installed during
a previous repair. Point them out to the customer
and recommend their replacement.
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, mU.S.t not exceed 0.5 mA (500 microampere).
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 milliameter. 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 mU.S.t have an accu-
rate 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 2V AC range are suitable. (See Fig. A)
SAFETY CHECK-OUT
(U.S. Model only)
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.
0.15 µF
Fig. A. usng an AC voltmeter to check AC leakage.
— 2 —
To Exposed Metal
Parts on Set
AC
1.5 k W Voltmeter
(0.75 V)
Earth Ground