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3. Microcomputer C (IC451)
Microcomputer
C
controls
LED
display,
and
should be checked when there are any abnormal-
ities in LED display.
@
Pins qd) - @) are input pins for data from
microcomputer
B. Check
that data is applied
to these pins when the power switch is turned
on and off.
@
Check
that
signals
are
being
output
from
output pins @) -
:
4. Microcomputer B (IC501)
This contorls microcomputers A and C and other
IC's. Therefore, this microcomputer should also be
checked
when
microcomputer
A
and/or C
is
thought to be defective.
MODE L IDENTIFICATION
— Specification Label —
SONY:
PROGRAM
EQUALIZER
WLLL
LLL
SEQ-555ES
MODEL NO.SEQ-555ES
US, Canadian model:
120V
60Hz
25W
AEP, E model:
120/220V
~
50/60Hz
25W
SAFETY
CHECK-OUT
(US Model)
After
correcting
the
original
service
problem,
perform the following safety check 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
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
0.5mA
(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 instru-
ments.
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 volt-
meter.
The
"limit"
indication
is 0.75V,
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)
|
weary
Fig. A.
Using an AC voltmeter to check AC leakage.
we
0.15 pF
S154:
voltmeter
(0.75 V)
_—
To Exposed Metal
Parts on Set
AC
Earth Ground
————__|
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