– 2 –
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.
Look for unauthorized replacement parts, par-ticularly
transistors, that were installed during a previous repair.
Point them out to the customer and recommend their
replacement.
4.
Look for parts which, through functioning, show obvious
signs of deterioration. Point them out to the customer and
recommend their replace-ment.
5.
Check the line cord for cracks and abrasion.
Recommend the replacement of any such line cord to the
customer.
6.
Check the B+ voltage to see it is at the values specified.
6.
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 form any exposed metal parts to earth ground
and from all exposed metal parts to any exposed metal part
having a return to chassis, must not exceed 0.5mA (500
microampers).
Leakage current can be measured by any one of three methods.
1. A commercial leakage tester, such as Simpson 229 or RCA
WT-540A. Follow the manufactures' instructions to use these
instruments.
2. A battery operated AC milliammerter. 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 0.75V, so analog meters must have an accurate
lowvoltage scale. The Simpson 250 and Sanwa SH-63Trd are
examples of a passive VOM that is suitable. Nearly all battery
operated digital multimeters that have a 2V AC range are
suitable. (See Fig. A)
SAFETY CHECK-OUT
After correcting the original service problem, perform the following
safety checks before releasing the set to the customer.
SAFETY-RELATED COMPONENT WARNING!!
COMPONENTS IDENTIFIED BY MARK
!
OR DOTTED LINE
WITH MARK
!
ON THE SCHEMATIC DIAGRAMS AND IN THE
PARTS LIST ARE CRITICAL TO SAFE OPERATION. REPLACE
THESE COMPONENTS WITH SONY PARTS WHOSE PART
NUMBERS APPEAR AS SHOWN IN THIS MANUAL OR IN
SUPPLEMENTS PUB-LISHED BY SONY.
To Exposed Metal
Parts on Set
0.15
µ
F
1.5 k
Ω
AC
Voltmeter
(0.75 V)
Earth Ground
Fig. A. Using an AC voltmeter to check AC leakage.
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