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CAUTION
Use of controls or adjustments or performance
of
procedures other than those specified herein may result in
hazardous radiation exposure.
Notes on chip component
replacement
« Never reuse a disconnected chip component.
* Notice that the minus side of a tantalum capacitor may be
damaged by heat.
Flexible Circuit Board Repairing
¢« Keep the temperature of the soldering iron around 270 °C
during repairing.
¢ Do not touch the soldering iron on the same conductor ofthe
circuit board (within 3 times).
¢ Be careful not to apply force on the conductor when soldering
or unsoldering.
SAFETY
CHECK-OUT
After correcting the original service problem, perform
the following safety checks before releasing the set to the
customer:
Check the antenna terminals, metal trim, "metallized"
knobs, screws, and all other exposed metal parts for AC
leakage. Check leakage as described below.
LEAKAGE
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" indication is-0.75 V, so analog meters must
have. an accurate low-voltage 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)
To Exposed Metal
Parts on Set
AC
es
voltmeter
(0.75V)
=
Earth Ground
Fig. A. Using an AC voltmeter to check AC leakage.
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