Sony SEQ-555ES - Model Identification; Leakage Test

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
————__|